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1

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

PubMed

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

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

2014-09-15

2

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

PubMed Central

A simple adhesive-tape-based method for sampling of tomato surfaces was combined with fluorescence in situ hybridization for rapid culture-independent detection of Salmonella strains. Tapes could also be placed face-down on selective agar for on-tape enrichment of captured Salmonella cells. Overlay of cell-charged tapes with small volumes of liquid enrichment media enabled subsequent detection of tape-captured Salmonella via flow cytometry. PMID:19124588

Bisha, Bledar; Brehm-Stecher, Byron F.

2009-01-01

3

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

PubMed

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

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

2014-07-01

4

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

2014-11-01

5

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

PubMed

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

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

2013-06-18

6

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

PubMed

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

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

2013-07-01

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

Simple pyridyl-salicylimine-based fluorescence "turn-on" sensors for distinct detections of Zn2+, Al3+ and OH- ions in mixed aqueous media.  

PubMed

Simple pyridyl-salicylimine derivatives (F1, F2 and F3) are reported for the first time as fluorescence "turn-on" sensors for distinct detections of Zn(2+), Al(3+) and OH(-) ions in mixed-aqueous media CH3CN/H2O with volume ratios of 6/4 and 3/7 (at pH = 7 and 25 °C) via internal charge transfer (ICT), chelation enhanced fluorescence (CHEF), and deprotonation mechanisms. F1 and F2 show diverse turn-on sensing applications to Zn(2+), Al(3+) and OH(-) ions, but F3 exhibited the fluorescence turn-on sensing to Al(3+) and OH(-) ions in CH3CN/H2O (6/4; vol/vol). F1+Zn(2+) and F2+Zn(2+) complexes revealed the reversibilities and ratiometric displacements of Zn(2+) with ethylene diamine tetra acetic acid (EDTA) and Al(3+) ions, respectively, in CH3CN/H2O (6/4; vol/vol). On the other hand, F1, F2 and F3 in CH3CN/H2O (3/7; vol/vol) showed sensitivities only to Al(3+) ions but negligible selectivities to OH(-) ions. Stoichiometry of all sensor complexes were calculated as 1 : 1 by job's plots based on UV/Vis and PL titrations. The complex formation and binding sites of all sensor materials were well characterized by (1)H, (13)C NMR, and mass (FAB) spectral analysis. Detection limits were calculated from standard deviations and linear fitting calculations. The association constant (log K(a)) values of sensor complexes were evaluated from the fluorescence binding isotherms. The fluorescence decay constant (?) values were estimated from time resolved fluorescence studies. Time, temperature, pH and solvent concentration effects towards sensor responses were fully investigated in this report. PMID:23531941

Shellaiah, Muthaiah; Wu, Yen-Hsing; Lin, Hong-Cheu

2013-05-21

9

Development of a simple fluorescence-based microplate method for the high-throughput analysis of proline in wine samples.  

PubMed

This paper presents a simple, accurate and multi-sample method for the determination of proline in wines thanks to a 96-well microplate technique. Proline is the most abundant amino acid in wine and is an important parameter related to wine characteristics or maturation processes of grape. In the current study, an improved application of the general method based on sodium hypochlorite oxidation and o-phthaldialdehyde (OPA)-thiol spectrofluorometric detection is described. The main interfering compounds for specific proline detection in wines are strongly reduced by selective reaction with OPA in a preliminary step under well-defined pH conditions. Application of the protocol after a 500-fold dilution of wine samples provides a working range between 0.02 and 2.90gL(-1), with a limit of detection of 7.50mgL(-1). Comparison and validation on real wine samples by ion-exchange chromatography prove that this procedure yields accurate results. Simplicity of the protocol used, with no need for centrifugation or filtration, organic solvents or high temperature enables its full implementation in plastic microplates and efficient application for routine analysis of proline in wines. PMID:24360450

Robert-Peillard, Fabien; Boudenne, Jean-Luc; Coulomb, Bruno

2014-05-01

10

Fluorescence-based biosensors.  

PubMed

The field of optical sensors has been a growing research area over the last three decades. A wide range of books and review articles has been published by experts in the field who have highlighted the advantages of optical sensing over other transduction methods. Fluorescence is by far the method most often applied and comes in a variety of schemes. Nowadays, one of the most common approaches in the field of optical biosensors is to combine the high sensitivity of fluorescence detection in combination with the high selectivity provided by ligand-binding proteins. In this chapter we deal with reviewing our recent results on the implementation of fluorescence-based sensors for monitoring environmentally hazardous gas molecules (e.g. nitric oxide, hydrogen sulfide). Reflectivity-based sensors, fluorescence correlation spectroscopy-based (FCS) systems, and sensors relying on the enhanced fluorescence emission on silver island films (SIFs) coupled to the total internal reflection fluorescence mode (TIRF) for the detection of gliadin and other prolamines considered toxic for celiac patients are also discussed herein. PMID:22573441

Strianese, Maria; Staiano, Maria; Ruggiero, Giuseppe; Labella, Tullio; Pellecchia, Claudio; D'Auria, Sabato

2012-01-01

11

Fluorescence Based Sensor Arrays  

Microsoft Academic Search

\\u000a Fluorescence-based cross reactive sensor arrays have experienced significant development in the last decade because of the\\u000a advantages that they can offer with respect to other transduction mechanisms, in terms of the usual performance parameters\\u000a such as sensitivity, selectivity and so on. From this point of view, a great impulse to this development has been due to the\\u000a realization of novel

Roberto Paolesse; Donato Monti; Francesca Dini; Corrado Di Natale

12

A simple and sensitive HPLC method based on pre-column fluorescence labelling for multiple classes of plant growth regulator determination in food samples.  

PubMed

The determination of trace plant growth regulator (PGR) has received more and more attentions in the field of phytophysiology and food safety. But the simple and sensitive method for simultaneously analysing multiple classes of PGR remains poorly investigated. In this study, a new pre-column fluorescence labelling method using 2-(11H-benzo[a]carbazol-11-yl)-ethyl-4-methylbenzenesulfonate (BCETS) as the labelling reagent has been developed for simultaneous determination of seven PGRs (i.e., indole-3-acetic acid, 3-indolybutyric acid, 3-indolepropionic acid, jasmonic acid, gibberellin A3, 1-naphthylacetic acid and 2-naphthaleneacetic acid) by HPLC with fluorescent detection (FLD). The proposed method offered the LOD of 0.34-0.73ng/mL for seven PGRs, which were significantly lower than the reported methods. The crude extract without complex pre-treatments and purification was directly labelled by BCETS and analysed by HPLC-FLD, which facilitates the high-throughput sample screening. This method was proven to be inexpensive, simple, selective, sensitive, accurate and reliable for trace PGR determination. PMID:25306326

Li, Guoliang; Liu, Shucheng; Sun, Zhiwei; Xia, Lian; Chen, Guang; You, Jinmao

2015-03-01

13

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

PubMed

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

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

2013-11-01

14

(2-Naphthoxy)acetyl chloride, a simple fluorescent reagent.  

PubMed

In continuing the search for fluorescent reagents for analytical derivatization in chromatography, we found a simple chemical, (2-naphthoxy)acetyl chloride, with potential fluorophore/chromophore characteristics for the highly sensitive detection of analytes with an amino function. The reagent has an auxochrome (a substituted alkoxy moiety) attached to the fluorophoric/chromophoric naphthalene system, resulting in favorable spectrophotometric properties. The reagent can be easily prepared from (2-naphthoxy)acetic acid and has been used in organic synthesis; it is initially introduced as a fluorescent reagent to derivatise amantadine and memantine (amino pharmaceuticals) as model analytes. The resulting naphthoxy derivatives of the drugs can be analyzed at sub-microM levels by HPLC with fluorimetric detection (excitation wavelength 227 nm, emission wavelength 348 nm). Application of the reagent to the fluorimetric derivatization of important biological amines for sensitive detection can be expected. PMID:12613813

Duh, Tsai-Hui; Wu, Hsin-Lung; Kou, Hwang-Shang; Lu, Chi-Yu

2003-02-14

15

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

16

Aluminum oxide nanostructure-based substrates for fluorescence enhancement.  

PubMed

A new fluorescence enhancement technical platform based on anodic aluminum oxide (AAO) nanostructure substrate is reported for the first time. Several fluorophores have been examined on the AAO nanostructure substrates. Systematic experiments found that the enhancement factor can be up to two orders of magnitude compared to the fluorescence signals on a glass substrate, indicating its great potential for ultrasensitive fluorescence detection. Given the simple and cost-effective fabrication process of lithographically patterned AAO nanostructure, this type of AAO nanostructure platform has great potential applications, especially its integration with microdevices and microfluidic devices for fluorescence-based biological analysis. PMID:23037250

Li, Xiang; He, Yuan; Zhang, Tianhua; Que, Long

2012-09-10

17

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

PubMed

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

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

2004-04-01

18

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

NASA Astrophysics Data System (ADS)

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

Badiei, Alireza; Goldooz, Hassan

19

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

20

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

21

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

PubMed

Nanoparticles are now utilized in many diverse biological and medical applications. Despite this, it remains challenging to tailor their surface for specific molecular targeting while maintaining high biocompatibility. To address this problem, we evaluate a phytochelatin-related peptide surface coating to produce functional and biocompatible nanoparticles (NPs) based on fluorescent InP/ZnS and CdSe/ZnS or superparamagnetic FePt and Fe(3)O(4). Using a combination of transmission electron microscopy, size-exclusion chromatography and gel electrophoresis (GE), we demonstrate the excellent colloidal properties of the peptide-coated NPs (pNPs) and the compact nature of the coating (?4 nm thickness). We develop a simple protocol for the monofunctionalization of the pNPs with targeting biomolecules, by combining covalent conjugation with GE purification. We then employ functionalized InP/ZnS pNPs in a live-cell, single-molecule imaging application to specifically target and detect individual proteins in the cell membrane. These findings showcase the versatility of the peptides for preparing compact NPs of various compositions and sizes, which are easily functionalized, and suitable for a broad range of biomedical applications. PMID:21411925

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

2011-04-29

22

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

23

Implantable fluorescence-based glucose sensor development  

NASA Astrophysics Data System (ADS)

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

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

2005-03-01

24

Fluorescence lifetime-based sensing and imaging  

Microsoft Academic Search

Time-resolved fluorescence spectroscopy is presently regarded as a research tool in biochemistry, biophysics and chemical physics. However, time-resolved methods can also be used for chemical sensing. Lifetime-based sensing has several advantages over intensity-based methods. Since the lifetime is independent of the total probe intensity, its measurement can provide quantitative sensing of many analytes without the requirement for wavelength-ratiometric probes. Analytes

Henryk Szmacinski; Joseph R. Lakowicz

1995-01-01

25

Fluorescent Proton Sensors Based On Energy Transfer  

PubMed Central

Photophysical data and orbital energy levels (from electrochemistry) were compared for molecules with the same BODIPY acceptor part (red) and perpendicularly oriented xanthene or BODIPY donor fragments (green). Transfer of energy, hence the photophysical properties of the cassettes, including the pH dependant fluorescence in the xanthene containing molecules, correlates with the relative energies of the frontier orbitals in these systems. Intracellular sensing of protons is often achieved via sensors that switch off completely at certain pH values, but probes of this type are not easy to locate inside cells in their “off-state”. A communication from these laboratories (J. Am. Chem. Soc., 2009, 131, 1642 – 3) described how the energy transfer cassette 1 could be used for intracellular imaging of pH. This probe is fluorescent whatever the pH, but its exact photophysical properties are governed by the protonation-states of the xanthene donors. This work was undertaken to further investigate correlations between structure, photophysical properties, and pH for energy transfer cassettes. To achieve this, three other cassettes 2 – 4 were prepared another one containing pH-sensitive xanthene donors (2), and two “control cassettes” that each have two BODIPY-based donors (3 and 4). Both the cassettes 1 and 2 with xanthene-based donors fluoresce red under slightly acidic conditions (pH < ca 6), and green when the medium is more basic (> ca 7), whereas the corresponding cassettes with BODIPY donors give almost complete energy transfer regardless of pH. The cassettes that have BODIPY donors by contrast, show no significant fluorescence from the donor parts, but the overall quantum yields of the cassettes when excited at the donor (observation of acceptor fluorescence) are high (ca 0.6 and 0.9). Electrochemical measurements were performed to elucidate orbital energy level differences between the pH-fluorescence profiles of cassettes with xanthene donors, relative to the two with BODIPY donors. These studies confirm energy transfer in the cassettes is dramatically altered by analytes that perturb relative orbital levels. Energy transfer cassettes with distinct fluorescent donor and acceptor units provide a new, and potentially useful, approach to sensors for biomedical applications. PMID:21618970

Thivierge, Cliferson; Han, Junyan; Jenkins, Roxanne M.

2011-01-01

26

Adaptive finite element based tomography for fluorescence optical  

E-print Network

Adaptive finite element based tomography for fluorescence optical imaging in tissue Amit Joshi,1@ices.utexas.edu, eva-m-sevick@tamu.edu Abstract: A three-dimensional fluorescence-enhanced optical tomogra- phy scheme based upon an adaptive finite element formulation is developed and employed to reconstruct fluorescent

Bangerth, Wolfgang

27

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

28

Simple road detection based on vanishing point  

NASA Astrophysics Data System (ADS)

Vision-based road detection is one of the key techniques of autonomous driving, intelligent vehicles, and visual navigation. At present, methods based on vanishing point perform best with general roads. However, it is difficult for them to meet the needs of a real-time system due to high time consumption. This paper presents a fast detection method, namely simple road detection, which achieves high efficiency by employing sky segmentation and two new optimization schemes-sample convolution and fast voting. The optimizations are based on lookup tables, sample computing, and computing simplification. The interval sampling in sample convolution makes the proposed method flexible to meet various efficiency and accuracy demands by different sample-step values. Mean filter and vote orientation limitation are also proposed to help improve detection accuracy. Experiments have been conducted with a large number of road images under different environmental conditions, and the results demonstrate that our proposed method is efficient and effective in detecting both structured and unstructured roads.

Ziyu, Chen; Zhen, He

2014-05-01

29

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

PubMed Central

In the recent years, the use of light emitting diodes (LEDs) has become commonplace in fluorescence microscopy. LEDs are economical, easy to couple to commercial microscopes and provide powerful and stable light that can be triggered by TTL pulses in the range of tens of microseconds or shorter. LEDs are usually installed on the epifluorescence port of the microscope to obtain whole field illumination which is ideal for fluorescence imaging. In contrast, photolysis or channelrhodopsin stimulation often requires localised illumination, typically achieved using lasers. Here we show that insertion of a long-pass (>411 nm) filter with appropriately sized pinhole in the epifluorescence pathway, combined with dual UV/visible illumination, can produce efficient whole field visible illumination and spot UV illumination of 15–20 ?m. We tested our system by performing calcium imaging experiments combined with L-glutamate or NMDA photo-release in hippocampal neurons from brain slices or dissociated cultures, demonstrating the ability to obtain local activation of NMDA receptors exclusively in the illuminated spot. The very inexpensive and simple system that we report here will allow many laboratories with limited budget to run similar experiments in a variety of physiological applications. PMID:23764747

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

2013-01-01

30

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

31

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

32

A general fluorescence-based coupled assay for S-adenosylmethionine-dependent methyltransferases  

E-print Network

Available online 2 April 2005 Abstract We have developed a simple and sensitive fluorescence-based two assays for these enzymes. Most existing assays for MTases rely on costly radio-labeled materials, time­7]. Recently, a three-step coupled enzymatic assay for salicylic acid car- boxyl MTase based on absorption

Hrycyna, Christine A.

33

Fluorescence-lifetime-based sensing: applications to clinical chemistry and cellular imaging  

NASA Astrophysics Data System (ADS)

Measurements of fluorescence lifetimes, rather than intensity or intensity ratios, offer many advantages in clinical chemistry and imaging. However, measurements of time-resolved fluorescence are normally associated with complex laser light sources and instrumentation. In this lecture, we show how emerging technology is enabling the design and use of simple instrumentation for time-resolved fluorescence. In particular, it is now possible to imagine lifetime-based measurements of blood gases and blood glucose, and lifetime imaging of calcium and other ions in microscopic samples.

Lakowicz, Joseph R.; Szmacinski, Henryk; Thompson, Richard B.

1993-06-01

34

A SIMPLE FLUORESCENT LABELING METHOD FOR STUDIES OF PROTEIN OXIDATION, PROTEIN MODIFICATION, AND PROTEOLYSIS  

PubMed Central

Proteins are sensitive to oxidation, and oxidized proteins are excellent substrates for degradation by proteolytic enzymes such as the Proteasome and the mitochondrial Lon protease. Protein labeling is required for studies of protein turnover. Unfortunately, most labeling techniques involve 3H or 14C methylation which is expensive, exposes researchers to radioactivity, generates large amounts of radioactive waste, and allows only single-point assays because samples require acid-precipitation. Alternative labeling methods, have largely proven unsuitable, either because the probe itself is modified by the oxidant(s) being studied, or because the alternative labeling techniques are too complex or too costly for routine use. What is needed is a simple, quick, and cheap labeling technique that uses a non-radioactive marker, that binds strongly to proteins, is resistant to oxidative modification, and emits a strong signal. We have devised a new reductive method for labeling free carboxyl groups of proteins with the small fluorophore 7-amino-4-methycoumarin (AMC). When bound to target proteins, AMC fluoresces very weakly but when AMC is released by proteinases, proteases, or peptidases, it fluoresces strongly. Thus, without acid-precipitation, the proteolysis of any target protein can be studied continuously, in multiwell plates. In direct comparisons, 3H-labeled proteins and AMC-labeled proteins exhibited essentially identical degradation patterns during incubation with trypsin, cell extracts, and purified proteasome. AMC-labeled proteins are well-suited to study increased proteolytic susceptibility following protein modification, since the AMC-protein bond is resistant to oxidizing agents such as hydrogen peroxide and peroxynitrite, and is stable over time and to extremes of pH, temperature (even boiling), freeze-thawing, mercaptoethanol, and methanol. PMID:21988844

Pickering, Andrew. M.; Davies, Kelvin. J. A.

2014-01-01

35

Time resolved fluorescence tomography of turbid media based on lifetime  

E-print Network

Time resolved fluorescence tomography of turbid media based on lifetime contrast Anand T. N. Kumar-based analysis of the entire temporal fluorescence response from a turbid medium. Simulations are used to show, (170.3650) Lifetime-based sensing, (170.6920) Time-resolved imaging, (170.7050) Turbid media References

Kumar, Anand T.N.

36

Fluorescence sensor for Cu(II) in the serum sample based on click chemistry.  

PubMed

Cu(II) can be reduced to Cu(I) by sodium ascorbate (SA) in situ, which in turn induces CuAAC reaction between the weak fluorescent compound (3-azido-7-hydroxycoumarin) and propargyl alcohol to form a strong fluorescent compound. Based on such principle, a simple and sensitive fluorescence sensor for Cu(II) can be developed, which combines the character of high selectivity of click chemistry and high sensitivity of fluorescence detection. The value of fluorescence increase factor shows a good linear relationship with the concentration of Cu(II) in the range of 0.25 ?M-2.5 ?M with a detection limit of 0.08 ?M. In addition, the developed sensor shows high selectivity towards Cu(II) assay even in the presence of other common metal ions and it has been successfully applied to detect Cu(II) in human serum with satisfactory results. PMID:24350327

Wang, Chunmei; Lu, Lijun; Ye, Wenmei; Zheng, Ou; Qiu, Bin; Lin, Zhenyu; Guo, Longhua; Chen, Guonan

2014-02-01

37

Simple, rapid and inexpensive quantitative fluorescent PCR method for detection of microdeletion and microduplication syndromes.  

PubMed

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

38

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

2013-01-01

39

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

40

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...

41

Capillary scale liquid core waveguide based fluorescence detectors for liquid chromatography and flow analysis  

Microsoft Academic Search

A versatile, simple, liquid core waveguide (LCW)-based fluorescence detector design is described for capillary systems. A Teflon AF coated fused silica capillary serves as the LCW. The LCW is transversely excited. The light source can be a conventional or high power (HP) light emitting diode (LED) or a laser diode (LD). The source can be coupled to the LCW directly

Guanqun Song; Ignacio Villanueva-Fierro; Shin-Ichi Ohira; Santosh Mishra; Howard Bailiff; Charles R. Savage; Purnendu K. Dasgupta

2008-01-01

42

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

EPA Science Inventory

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

43

Fluorescence-based optical glucose sensing  

E-print Network

Previous studies have indicated that optical means of blood glucose detection are feasible and provide a minimally invasive alternative to current commercially available modalities. Fluorescence spectroscopy has shown promise in many examples...

Meledeo, Michael Adam

2012-06-07

44

A label-free fluorescent aptamer sensor based on regulation of malachite green fluorescence  

PubMed Central

We report a label-free fluorescent aptamer sensor for adenosine based on the regulation of malachite green (MG) fluorescence, with comparable sensitivity and selectivity to other labeled adenosine aptamer-based sensors. The sensor consists of free MG, an aptamer strand containing an adenosine aptamer next to an MG aptamer, and a bridging strand that partially hybridizes to the aptamer strand. Such a hybridization prevents MG from binding to MG aptamer, resulting in low fluorescence of MG in the absence of adenosine. Addition of adenosine causes the adenosine aptamer to bind adenosine, weakening the hybridization of the aptamer strand with the bridging strand, making it possible for MG to bind to the aptamer strand and exhibits high fluorescence intensity. Since this design is based purely on nucleic acid hybridization, it can be generally applied to other aptamers for the label-free detection of a broad range of analytes. PMID:20017558

Xu, Weichen; Lu, Yi

2009-01-01

45

Phytoplankton photocompensation from space-based fluorescence measurements  

NASA Astrophysics Data System (ADS)

Recent satellite-derived observations linked global scale phytoplankton fluorescence variability with iron stress and hinted at photophysiological responses associated with changing light levels. These photocompensation reactions, the sum of photoacclimation and photoadaptation, were examined with climatological data for the Gulf of Maine. Significant seasonal variability was observed in the fluorescence quantum yield that was unrelated to patterns of biomass. Up to 89% of the variability in the fluorescence quantum yield was explained by a physiology-based photocompensation model. Spatial variability in seasonal patterns was associated with differing hydrodynamic regimes. This variability in the quantum yield demonstrates that satellite-based fluorescence is inappropriate for phytoplankton biomass determinations. More importantly, the work presented here provides the modeling foundation for fluorescence-based investigations of temporal and spatial variability in phytoplankton physiology associated with growth irradiance. These space-based physiological observations have the potential to decrease uncertainties in future ocean color derived primary productivity estimates.

Morrison, J. Ruairidh; Goodwin, Deborah S.

2010-03-01

46

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

47

Rapid and ratiometric fluorescent detection of cysteine with high selectivity and sensitivity by a simple and readily available probe.  

PubMed

We report a simple and readily available fluorescent probe for rapid, specific, and ratiometric fluorescent detection of the biologically important cysteine (Cys). This probe uses a visible-light excitable excited-state intramolecular proton transfer (ESIPT) dye (4'-dimethylamino-3-hydroxyflavone) as the fluorophore and an acrylate group as the ESIPT blocking agent as well as the recognition unit. Cleavage of the acrylate moiety can be achieved specifically and rapidly by Cys in aqueous solution under mild conditions, which leads to restore the ESIPT process and enables the probe to show a rapid, ratiometric fluorescent detection process for Cys with high selectivity over various analytes, including homocysteine (Hcy) and glutathione (GSH). The detection limit of this probe for Cys was found to be ?0.2 ?M and bioimaging of intracellular Cys by this probe was successfully applied in living cells, indicating that this probe holds great potential for biological applications. PMID:25253409

Liu, Yao; Yu, Dehuan; Ding, Shuangshuang; Xiao, Qi; Guo, Jun; Feng, Guoqiang

2014-10-22

48

Fluorescence-based resource for semi-automated genomic analyses  

SciTech Connect

To facilitate the practical application of highly efficient semi-automated methods for general application in genomic analyses, we have developed a fluorescence-based marker resource. Ninety highly polymorphic simple tandem repeat markers were combined to provide a rapid, accurate, and highly efficient initial genome-wide screening system. These markers are spaced on average every 33 recombination units, with a mean heterozygosity of 81% (range 65-94%), covering 22 autosomes and the X and Y chromosomes. Less than 3% of the genome lies beyond 30 cM of the nearest marker. Markers were placed in a vertical ladder that we have termed a SET according to the size of the PCR fragments they produce during electrophoresis. Each SET was designed to avoid overlap between loci during gel separations to assure accuracy when scoring genotypes. We have constructed 15 SETS of markers. Three SETS, each labelled with one of three fluors, were combined into what we have termed a GROUP, which is co-electrophoresed with internal size standards that are labelled with a fourth flour. Five GROUPS of markers were assembled that contain a total of 15 SETS of markers. Each GROUP cover 18 regions of the genome that can be detected simultaneously, since this genomic analysis system is fully compatible with automated fragment analyzers using simultaneous four-color fluorescence-based detection systems. This allows for multiplex detection and a throughput of 1,944 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.

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

1994-09-01

49

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.  

Code of Federal Regulations, 2012 CFR

...false Bare or covered (no reflector) medium base compact fluorescent lamps. 429...35 Bare or covered (no reflector) medium base compact fluorescent lamps. ...applicable to bare or covered (no reflector) medium base compact fluorescent lamps;...

2012-01-01

50

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.  

...false Bare or covered (no reflector) medium base compact fluorescent lamps. 429...35 Bare or covered (no reflector) medium base compact fluorescent lamps. ...applicable to bare or covered (no reflector) medium base compact fluorescent lamps;...

2014-01-01

51

10 CFR 429.35 - Bare or covered (no reflector) medium base compact fluorescent lamps.  

Code of Federal Regulations, 2013 CFR

...false Bare or covered (no reflector) medium base compact fluorescent lamps. 429...35 Bare or covered (no reflector) medium base compact fluorescent lamps. ...applicable to bare or covered (no reflector) medium base compact fluorescent lamps;...

2013-01-01

52

Reversible "off-on" fluorescent chemosensor for Hg2+ based on rhodamine derivative.  

PubMed

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, (1)H 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. PMID:22018584

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

2012-01-01

53

Highly fluorescent BF2 complexes of hydrazine-Schiff base linked bispyrrole.  

PubMed

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

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

2014-06-01

54

Selective chemosensor for copper ions based on fluorescence quenching of a Schiff-base fluorophore.  

PubMed

A Schiff base-based fluorescent chemosensor has been studied for divalent copper detection. The formation of 2-hydroxybenzaldehyde benzoylhydrazone-Cu(2+) complex induced a fluorescence quenching of this compound in a medium of water/ethanol (53% v/v) and 0.05 M phosphate buffer (pH 7.0). The continuous variations and mole-ratio plots of absorbance suggested a complex formation with a 1:1 metal-ligand stoichiometry. The conditional stability constant for the complex was evaluated to be 6 x 10(6) M(-1). A modified Stern-Volmer relationship was employed to obtain a linear calibration plot, obtaining a dynamic working range up to 157.4 microM. The detection limit of this system was found to be 5.6 microM and the relative standard deviation for five measurements of 78.7 microM concentration was 5.2%. This fluorescent chemosensor also showed a high selectivity for copper ions over other metal ions, such as Al(3+), Ca(2+), Cd(2+), Fe(2+), K(+), Mg(2+), Na(+), Pb(2+), or Zn(2+). The results of this investigation show a simple, rapid, low-cost, and selective method that can operate in neutral solutions and is useful for biological and environmental applications. PMID:20615285

Espada-Bellido, Estrella; Galindo-Riaño, Maria Dolores; García-Vargas, Manuel; Narayanaswamy, Ramaier

2010-07-01

55

Fluorescent ester dye-based assays for the in vitro measurement of Neospora caninum proliferation.  

PubMed

Techniques for the measurement of parasite loads in different experimental models have evolved throughout the years. The quantification of stained slides using regular cytological stains is currently the most common technique. However, this modality of evaluation is labor-intensive, and the interpretation of the results is subjective because the successes of the assays mainly rely on the abilities of the professionals involved. Moreover, the novel genetic manipulation techniques that are commonly applied for closely related Toxoplasma gondii have not yet been developed for Neospora caninum. Thus, we aimed to develop a simple protocol for parasite quantification using pre-stained N. caninum tachyzoites and fluorescent probes based on ester compounds (i.e., CFSE and DDAO). For this purpose, we employed a quantification procedure based on flow cytometry analysis. Pre-stained parasites were also examined with a fluorescent microscope, which revealed that both dyes were detectable. Direct comparison of the numbers of CFSE+ and DDAO+ cells to the values obtained with classical cytology techniques yielded statistically comparable results that also accorded with genomic DNA amplification results. Although the fluorescence emitted by DDAO was more intense and provided better discrimination between the populations of parasitized cells, CFSE+ tachyzoites were detected for several days. In conclusion, this study describes a simple, fast, low-cost and reproducible protocol for N. caninum quantification that is based on parasite pre-staining with fluorescent ester-based probes. PMID:25095733

Mota, Caroline M; Ferreira, Marcela D; Costa, Lourenço F; Barros, Patrício S C; Silva, Murilo V; Santiago, Fernanda M; Mineo, José R; Mineo, Tiago W P

2014-09-15

56

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

PubMed

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

Ray, Debarati; Dalapati, Sasanka; Guchhait, Nikhil

2013-11-01

57

Continuous wave-based multiphoton excitation fluorescence for capillary electrophoresis  

Microsoft Academic Search

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

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

2006-01-01

58

Quinoline-based, glucose-pendant fluorescent zinc probes.  

PubMed

Quinoline-based tetradentate ligands with glucose pendants, N,N'-bis[2-(?-d-glucopyranosyloxy)ethyl]-N,N'-bis[(6-methoxyquinolin-2-yl)methyl]ethylenediamine (N,N'-6-MeOBQBGEN) and its N,N-counterpart, N,N-6-MeOBQBGEN, have been prepared, and their fluorescence-spectral changes upon Zn binding were investigated. Upon excitation at 336 nm, N,N'-6-MeOBQBGEN showed weak fluorescence (? ? 0.016) in HEPES buffer (HEPES 50 mM, KCl 100 mM, pH 7.5). In the presence of Zn, N,N'-6-MeOBQBGEN exhibited a significant increase in fluorescence (? = 0.096) at 414 nm. The fluorescence enhancement is specific for Zn and Cd (I(Cd) /I(Zn) of 50% at 414 nm). On the other hand, N,N-6-MeOBQBGEN exhibited a smaller fluorescence enhancement upon Zn complexation (? = 0.043, ?(ex) = 334 nm, ?(em) = 407 nm) compared with N,N'-6-MeOBQBGEN. Fluorescence microscopic analysis using PC-12 rat adrenal cells revealed that N,N'-6-MeOBQBGEN exhibits a 1.8-fold higher fluorescence-signal response to Zn ion concentration compared with sugar-depleted compound 2 (N,N'-bis[(6-methoxyquinolin-2-yl)methyl]ethylenediamine), due to its enhanced uptake into cells due to the targeting ability of the attached carbohydrates. PMID:22976991

Mikata, Yuji; Ugai, Anna; Yasuda, Keiko; Itami, Saori; Tamotsu, Satoshi; Konno, Hideo; Iwatsuki, Satoshi

2012-09-01

59

Doped semiconductor nanocrystal based fluorescent cellular imaging probes.  

PubMed

Doped semiconductor nanocrystals such as Mn doped ZnS, Mn doped ZnSe and Cu doped InZnS, are considered as new classes of fluorescent biological probes with low toxicity. Although the synthesis in high quality of such nanomaterials is now well established, transforming them into functional fluorescent probes remains a challenge. Here we report a fluorescent cellular imaging probe made of high quality doped semiconductor nanocrystals. We have identified two different coating approaches suitable for transforming the as synthesized hydrophobic doped semiconductor nanocrystals into water-soluble functional nanoparticles. Following these approaches we have synthesized TAT-peptide- and folate-functionalized nanoparticles of 10-80 nm hydrodynamic diameter and used them as a fluorescent cell label. The results shows that doped semiconductor nanocrystals can be an attractive alternative for conventional cadmium based quantum dots with low toxicity. PMID:23674276

Maity, Amit Ranjan; Palmal, Sharbari; Basiruddin, S K; Karan, Niladri Sekhar; Sarkar, Suresh; Pradhan, Narayan; Jana, Nikhil R

2013-06-21

60

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

PubMed

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

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

2014-03-01

61

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

62

Transparency-based microplates for fluorescence quantification.  

PubMed

Microplates for use in resource-limited laboratories should ideally not require processes that involve substantial large-scale production in order to be viable. We describe and demonstrate here an approach of using a silicone sheet with holes, conveniently cut out precisely using an inexpensive cutting plotter to correspond with regions where liquid is to be dispensed, and attaching it to a transparency to create very thin well arrays. With this, the contact angle hysteresis behavior of liquid could be harnessed to produce taller drop shapes so that the fiber probe used could read in the emitted light more effectively. Experimentation conducted revealed fluorescence measurements that were significantly more sensitive than standard microplates, notwithstanding that smaller volumes of liquid were needed. This was achieved using both the fiber optic and imaging evaluation modes. The two methods investigated, one with a lid placed and one without, showed the latter to produce marginally more sensitive readings as opposed to improved immunity from the environment with the former. These favorable measurement characteristics were found to be achievable with an estimated production cost of AU $0.40 and fabrication times of 3.5 min (96 wells) and 6.5 min (384 wells) per plate. PMID:22266206

Cheong, Brandon Huey-Ping; Diep, Vu; Ng, Tuck Wah; Liew, Oi Wah

2012-03-01

63

Recent progress on polymer-based fluorescent and colorimetric chemosensors.  

PubMed

Recently, fluorescent or colorimetric chemosensors based on polymers have attracted great attention due to several important advantages, such as their simplicity of use, signal amplification, easy fabrication into devices, and combination of different outputs, etc. This tutorial review will cover polymer-based optical chemosensors from 2007 to 2010. PMID:21107482

Kim, Ha Na; Guo, Zhiqian; Zhu, Weihong; Yoon, Juyoung; Tian, He

2011-01-01

64

Continuous wave-based multiphoton excitation fluorescence for capillary electrophoresis.  

PubMed

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

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

2006-03-24

65

Simple fluorescent enzyme immunoassay for detection and quantification of hepatitis C viremia  

Microsoft Academic Search

Background\\/Aims: The viral load of hepatitis C virus, as reflected by hepatitis C virus viremia, has been shown to have important clinical implications. In this study the hepatitis C virus core protein level in serum was evaluated for the detection and quantification of hepatitis C virus viremia.Methods: Hepatitis C virus core protein in serum was detected using a simple and

Takeshi Tanaka; Johnson Y. N. Lau; Masashi Mizokami; Etsuro Orito; Eiji Tanaka; Kendo Kiyosawa; Koichiro Yasui; Yohsuke Ohta; Akira Hasegawa; Satoshi Tanaka; Michinori Kohara

1995-01-01

66

Fluorescence lifetime-based glucose sensor using NADH  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

67

A Rapid Fluorescence-based Assay for Soluble Methane Monooxgyenase  

SciTech Connect

A fluorescence-based assay was developed to estimate soluble methane monooxygenase (sMMO) activity in solution. Whole cells of Methylosinus trichosporium OB3b expressing sMMO were used to oxidize various compounds to screen for fluorescent products. Of the 12 compounds tested, only coumarin yielded a fluorescent product. The UV absorbance spectrum of the product matches that of 7-hydroxycoumarin, and this identification was confirmed by 13C-NMR spectroscopy. The dependence of the fluorescent reaction on sMMO activity was investigated by pre-incubation with acetylene, a known inhibitor of sMMO activity. Apparent kinetic parameters for whole cells were determined to be Km(app)=262 µM and Vmax(app)=821 nmol 7-hydroxycoumarin min–1 mg protein–1. The rate of coumarin oxidation by sMMO correlates well with those of trichloroethylene degradation and naphthalene oxidation. Advantages of the fluorescence-based coumarin oxidation assay over the naphthalene oxidation assay include a more stable product, direct detection of the product without additional reagents, and greater speed and convenience.

Miller, Amber Reese; Keener, William Kelvin; Roberto, Francisco Figueroa; Watwood, Maribeth E.

2002-01-01

68

Analysis of plasma catecholamines by high-performance liquid chromatography with fluorescence detection: simple sample preparation for pre-column fluorescence derivatization.  

PubMed

Analysis of plasma catecholamines (norepinephrine, epinephrine and dopamine) by high-performance liquid chromatography using 1,2-diphenylethylenediamine as a fluorescent reagent is described. We have developed an automatic catecholamine analyser, based on pre-column fluorescence derivatization and column switching. The analysis time for one assay was 15 min. The correlation coefficients of the linear regression equations were greater than 0.9996 in the range 10-10,000 pg/ml. The detection limit, at a signal-to-noise ratio of 3, was 2 pg/ml for dopamine. A new method of sample preparation for the pre-column fluorescence derivatization of plasma catecholamines was used. In order to protect the catecholamines from decomposition, an ion-pair complex between boric acid and the diol group in the catecholamine was formed at a weakly alkaline pH. The stabilities of plasma catecholamines were evaluated at several temperatures. After complex formation, the catecholamines were very stable at 17 degrees C for 8 h, and the coefficients of variation for norepinephrine, epinephrine and dopamine were 1.2, 4.2 and 9.3%, respectively. PMID:1939468

Kamahori, M; Taki, M; Watanabe, Y; Miura, J

1991-07-01

69

A general fluorescence-based coupled assay for S-adenosylmethionine-dependent methyltransferases.  

PubMed

We have developed a simple and sensitive fluorescence-based two-step coupled enzyme assay to report the activity of S-adenosylmethionine-dependent methyltransferases. This assay relies on a fluorescein-cystamine-methyl red (FL-S-S-MR) reporter molecule that can be activated by thiols. In the absence of thiols, fluorescence from the reporter is quenched through fluorescence resonance energy transfer between the two chromophores. In this report, we use catechol-O-methyltransferase with the addition of S-adenosylhomocysteine hydrolase to produce the thiol homocysteine. The presence of homocysteine leads to disulfide bond cleavage in the cystamine tether and fluorescence dequenching as the uncoupled chromophores are diluted into the surrounding media. The sensitivity and specificity of FL-S-S-MR to thiols enabled detection of fluorescence reporter approach may be generalizable to all enzymatic or chemical assays that produce thiols. PMID:15845399

Wang, Caihua; Leffler, Scott; Thompson, David H; Hrycyna, Christine A

2005-05-27

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

2014-10-15

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

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

73

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

PubMed Central

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.

2013-01-01

74

Keep It Simple: A Case-Base Maintenance Policy Based on Clustering and Information  

E-print Network

Keep It Simple: A Case-Base Maintenance Policy Based on Clustering and Information Theory Qiang in this distributed case-base network, we present a method that is based on a decision forest built Heidelberg 2000 #12;Keep It Simple 103 on the speed and quality of the case base retrieval process

Yang, Qiang

75

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

76

Simple HPLC evaluation of lipoamidase activity in tissue using a newly synthesized fluorescent substrate, dansyl-?-lipoyllysine.  

PubMed

?-Lipoic acid (LA) is a naturally occurring disulfide-containing compound used as an antioxidant supplement which also has been used as a medicine for diabetic neuropathy in Europe. Physiologically LA acts as a coenzyme of mitochondrial multienzyme complex in its protein bound form but it is not yet clear how the externally administrated LA is incorporated into other proteins in the same protein-bound form or why the bound form is active as an antioxidant. The binding and cleavage of LA to or from the protein is mediated by lipoamidase and thus determines LA distribution in tissues. We have developed a simple sensitive assay for lipoamidase using a fluorescent substrate, dansyl-?-lipoyllysine (DLL). Lipoamidase in tissues cleaves the amide bond between LA and the ?-amino-lysine moiety to release dansylated lysine (DL). A HPLC comparison of the fluorescence intensity between DLL and DL was used to quantify the enzyme activity. The hydrolytic reaction did not occur when the tissue was heat-treated before incubation with DLL and was inhibited by free LA, especially by the R-enantiomer of LA (physiologically active form). N(?)-Acetyl-L-lysine did not compete with DLL in the cleavage reaction. The method was applied for the determination of lipoamidase activity levels in various rat tissues. It was revealed the spleen had the highest activity followed by the kidney, heart, lung and liver. The activity in the brain was below the detection limit of the assay. PMID:22293216

Motafakkerazad, Rouhollah; Wang, Man-Yuan; Wada, Naoki; Matsugo, Seiichi; Konishi, Tetsuya

2011-01-01

77

Simple Method to Enhance the Photostability of the Fluorescence Reporter R6G for Prolonged Single Molecule Studies  

PubMed Central

For fluorescence-based single-molecule studies, photobleaching of the dye reporter often limits the time window over which individual molecules can be followed. As such, many strategies, for example using a cocktail of chemical reagents, have been developed to decrease the rate of photobleaching. Herein, we introduce a new and highly effective method to enhance the photostability of one of the commonly used fluorescent dyes, rhodamine 6G (R6G). We show that micron-sized polydimethylsiloxane (PDMS) wells, when the PDMS surface is properly treated, not only provide a confined environment for single-molecule detection, but can also significantly increase the survival time of individual R6G molecules before photobleaching. Moreover, our results suggest, consistent with several previous studies, that R6G photobleaching involves a radical state. PMID:23641719

Guo, Lin; Gai, Feng

2013-01-01

78

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

PubMed

We demonstrate a simple method of stretching DNA to its full length, suitable for optical imaging and atomic force microscopy (AFM). Two competing forces on the DNA molecules, which are the electrostatic attraction between positively charged dye molecules (YOYO-1) intercalated into DNA and the negatively charged surface of glass substrate, and the centrifugal force of the rotating substrate, are mainly responsible for the effective stretching and the dispersion of single strands of DNA. The density of stretched DNA molecules could be controlled by the concentration of the dye-stained DNA solution. Stretching of single DNA molecules was confirmed by AFM imaging and the photoluminescence spectra of single DNA molecule stained with YOYO-1 were obtained, suggesting that our method is useful for spectroscopic analysis of DNA at the single molecule level. PMID:24407597

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

2014-05-01

79

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

PubMed Central

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

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

2007-01-01

80

Synthesis and fluorescence characteristics of ATP-based FRET probes.  

PubMed

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

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

2013-12-28

81

Electrospun sol-gel fibers for fluorescence-based sensing  

NASA Astrophysics Data System (ADS)

Fluorescence based biosensors have the ability to provide reliable pathogen detection. However, the performance could be improved by enhancing the effective surface area of the biosensor. We report on a new nanofibrous fluorescencebased biosensor, whereas a sol-gel platform mesh was constructed by utilizing electrospinning techniques. Furthermore, incorporating cetyltrimethylammonium bromide (CTAB) and conducting pore-forming techniques resulted in a high surface area material suitable for biosensor immobilization. The biosensor was designed to detect Helicobacter hepaticus bacterium by sandwiching the pathogen between two antibodies, one labeled with Alexa Fluor 546 fluorescent dye and the other with 20nm Au nanoparticles. In the presence of pathogen, the close proximity of Au nanoparticles quenched the Alexa Fluor fluorescence, suggesting that the electrospun fiber platforms are suitable for sensing H. Hepaticus. Additionally, sol-gel fibers used as biosensor platform have the added benefit of increased immobilization, as fluorescence intensity from immobilized biosensors is 8.5x106 cps higher on fibers than on a flat, non-porous substrate.

Memisevic, Jasenka; Riley, Lela; Grant, Sheila A.

2009-05-01

82

Simple linearization of measurement based on photovoltaic voltage  

NASA Astrophysics Data System (ADS)

Based on the logarithmic relationship between photovoltaic voltage and incident light intensity of a photo-detector, a simple and low-cost method is proposed to linearize the measurement of nonlinear variables related to light intensity. Theoretical analysis shows that this linear measurement method is feasible in a large measurement range if we choose a proper load resistance for the photodiode. Based on the Lambert-Beer law and the photovoltaic voltage-based measurement method, the linear measurements of liquid level and liquor concentration have been achieved experimentally by directly detecting the output voltage of a solar cell, and their nonlinearities are both less than 2.0%.

Li, Changsheng

2008-10-01

83

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

84

Simple super-resolution live-cell imaging based on diffusion-assisted Förster resonance energy transfer  

PubMed Central

Despite the recent development of several super-resolution fluorescence microscopic techniques, there are still few techniques that can be readily employed in conventional imaging systems. We present a very simple, rapid, general and cost-efficient super-resolution imaging method, which can be directly employed in a simple fluorescent imaging system with general fluorophores. Based on diffusion-assisted Förster resonance energy transfer (FRET), fluorescent donor molecules that label specific target structures can be stochastically quenched by diffusing acceptor molecules, thereby temporally separating otherwise spatially overlapped fluorescence signals and allowing super-resolution imaging. The proposed method provides two- to three-fold-enhancement in spatial resolution, a significant optical sectioning property, and favorable temporal resolution in live-cell imaging. We demonstrate super-resolution live-cell dynamic imaging using general fluorophores in a standard epi-fluorescence microscope with light-emitting diode (LED) illumination. Due to the simplicity of this approach, we expect that the proposed method will prove an attractive option for super-resolution imaging. PMID:23383376

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

2013-01-01

85

Two new rhodamine-based fluorescent chemosensors for Fe(3+) in aqueous solution.  

PubMed

Two new rhodamine-based fluorescent probes were synthesized and characterized by NMR, high resolution mass spectrometer (HR-MS) and IR. The probes displayed a high selectivity for Fe(3+) among environmentally and biologically relevant metal ions in aqueous solution (CH3 OH-H2 O?=?3 : 2, v/v). The significant changes in the fluorescence color could be used for naked-eye detection. Job's plot, IR and (1) H NMR indicated the formation of 1: 1 complexes between sensor 1 and Fe(3+) . The reversibility establishes the potential of both probes as chemosensors for Fe(3+) detection. The probe showed highly selectivity in aqueous solution and could be used over the pH range between 5 and 9. A simple paper test-strip system for the rapid monitoring of Fe(3+) was developed, indicating its convenient use in environmental samples. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24700778

Liu, Yaqi; Xu, Zhanhui; Wang, Jinhui; Zhang, Di; Ye, Yong; Zhao, Yufen

2014-11-01

86

Reaction-based fluorescent probe for detection of endogenous cyanide in real biological samples.  

PubMed

Herein, two compounds (1?a and 1?b) were rationally constructed as novel reaction-based fluorescent probes for CN(-) by making use of the electron-withdrawing ability of the cyano group that was formed from the sensing reaction. Notably, this design strategy was first employed for the development of fluorescent CN(-) probes. The experimental details showed that probe 1?a exhibited a fluorescence turn-on response to CN(-) , whereas other anions, biological thiols, and hydrogen sulfide gave almost no interference. The detection limit of probe 1?a for CN(-) was found to be 0.12??M. The sensing reaction product of 1?a with CN(-) was characterized by NMR spectroscopy and mass spectrometry. TD-DFT calculations demonstrated that the formed cyano group drives the intramolecular charge transfer (ICT) process from coumarin dye to the cyano group and thus the original strong ICT from the coumarin dye to the 3-position pyridyl vinyl ketone substituent is weakened, which results in recovery of coumarin fluorescence. The practical utility of 1?a was also examined. By fabricating paper strips, probe 1?a can be used as a simple tool to detect CN(-) in field measurements. Moreover, probe 1?a has been successfully applied for quantitative detection of endogenous CN(-) from cassava root. PMID:25156974

Long, Lingliang; Wang, Lin; Wu, Yanjun; Gong, Aihua; Da, Zulin; Zhang, Chi; Han, Zhixiang

2014-11-01

87

Fluorescent artificial enzyme-linked immunoassay system based on Pd/C nanocatalyst and fluorescent chemodosimeter.  

PubMed

Artificial enzyme mimics have recently attracted considerable interest because they possess many advantages compared with natural enzymes, such as low cost of preparation and high stability. Herein, we present a novel fluorescent artificial enzyme-linked immunoassay strategy by utilizing Pd/C nanocatalyst as the enzyme mimic and bis-allyloxycarbonyl rhodamine 110 (BI-Rho 110) as the substrate, and the amplification procedure is based on the palladium-catalyzed Tsuji-Trost reaction. Pd/C nanocatalyst with the average size of 150 nm was prepared by the impregnation-reduction method, and high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses reveal that Pd clusters with an average size of about 1 nm are dispersed uniformly on each carbon nanosphere's surface. Kinetic studies show that this reaction follows Michaelis-Menten kinetics and the fluorescence intensity is proportional to the concentration of Pd/C nanocatalyst under certain conditions. The turnover number of Pd/C nanocatalyst reaches up to 3.3 × 10(7) (h(-1)). The analytical performance of this system in detecting hCG shows that after a 24 h incubation the sensitivity limit can reach 0.1 ng/mL and the dynamic linear working range is 1-10 ng/mL. Our findings pave the way to use Pd-catalyzed reaction for design and development of novel analytical methods. PMID:24160777

Wang, Zhifei; Zheng, Shuang; Cai, Jin; Wang, Peng; Feng, Jie; Yang, Xia; Zhang, Liming; Ji, Min; Wu, Fugen; He, Nongyue; Wan, Neng

2013-12-01

88

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

89

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

90

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

PubMed Central

Sulfated polysaccharides (SP) from algae are of great interest due to their manifold biological activities. Obstacles to commercial (especially medical) application include considerable variability and complex chemical composition making the analysis and the quality control challenging. The aim of this study was to evaluate a simple microplate assay for screening the quality of SP. It is based on the fluorescence intensity (FI) increase of the sensor molecule Polymer-H by SP and was originally developed for direct quantification of SP. Exemplarily, 65 SP batches isolated from the red alga Delesseria sanguinea (D.s.-SP) and several other algae polysaccharides were investigated. Their FI increase in the Polymer-H assay was compared with other analytical parameters. By testing just one concentration of a D.s.-SP sample, quality deviations from the reference D.s.-SP and thus both batch-to-batch variability and stability can be detected. Further, structurally distinct SP showed to differ in their concentration-dependent FI profiles. By using corresponding reference compounds, the Polymer-H assay is therefore applicable as identification assay with high negative predictability. In conclusion, the Polymer-H assay showed to represent not only a simple method for quantification, but also for characterization identification and differentiation of SP of marine origin. PMID:24727392

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

2014-01-01

91

Simple and rapid quantification of gadolinium in urine and blood plasma samples by means of total reflection X-ray fluorescence (TXRF).  

PubMed

A simple and rapid method to determine gadolinium (Gd) concentrations in urine and blood plasma samples by means of total reflection X-ray fluorescence (TXRF) was developed. With a limit of detection (LOD) of 100 ?g L(-1) in urine and 80 ?g L(-1) in blood plasma and a limit of quantification (LOQ) of 330 ?g L(-1) in urine and 270 ?g L(-1) in blood plasma, it allows analyzing urine samples taken from magnetic resonance imaging (MRI) patients during a period of up to 20 hours after the administration of Gd-based MRI contrast agents by means of TXRF. By parallel determination of the urinary creatinine concentration, it was possible to monitor the excretion kinetics of Gd from the patient's body. The Gd concentration in blood plasma samples, taken immediately after an MRI examination, could be determined after rapid and easy sample preparation by centrifugation. All measurements were validated with inductively coupled plasma mass spectrometry (ICP-MS). TXRF is considered to be an attractive alternative for fast and simple Gd analysis in human body fluids during daily routine in clinical laboratories. PMID:21847492

Telgmann, Lena; Holtkamp, Michael; Künnemeyer, Jens; Gelhard, Carsten; Hartmann, Marcel; Klose, Annika; Sperling, Michael; Karst, Uwe

2011-10-01

92

Simple and rapid quality control of sulfated glycans by a fluorescence sensor assay--exemplarily developed for the sulfated polysaccharides from red algae Delesseria sanguinea.  

PubMed

Sulfated polysaccharides (SP) from algae are of great interest due to their manifold biological activities. Obstacles to commercial (especially medical) application include considerable variability and complex chemical composition making the analysis and the quality control challenging. The aim of this study was to evaluate a simple microplate assay for screening the quality of SP. It is based on the fluorescence intensity (FI) increase of the sensor molecule Polymer-H by SP and was originally developed for direct quantification of SP. Exemplarily, 65 SP batches isolated from the red alga Delesseria sanguinea (D.s.-SP) and several other algae polysaccharides were investigated. Their FI increase in the Polymer-H assay was compared with other analytical parameters. By testing just one concentration of a D.s.-SP sample, quality deviations from the reference D.s.-SP and thus both batch-to-batch variability and stability can be detected. Further, structurally distinct SP showed to differ in their concentration-dependent FI profiles. By using corresponding reference compounds, the Polymer-H assay is therefore applicable as identification assay with high negative predictability. In conclusion, the Polymer-H assay showed to represent not only a simple method for quantification, but also for characterization identification and differentiation of SP of marine origin. PMID:24727392

Lühn, Susanne; Grimm, Juliane C; Alban, Susanne

2014-04-01

93

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

94

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

PubMed

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

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

2013-08-14

95

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.

96

Conditionally fluorescent molecular probes for detecting single base changes in  

E-print Network

to pathogenic bac- teria or viruses3,4 . Consequently, the fast, simple and accurate detec- tion, analysis, dissociate slowly) and practically prevent the intended hybridization reactions. To achieve single molecules for single base changes. A comprehensive review of SNP detection methods is given in Kim and Misra

Zhang, David Yu

97

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

98

Miniature fiber optic sensor based on fluorescence energy transfer  

NASA Astrophysics Data System (ADS)

Optical fiber biosensors based on fluorescence assays have several distinct advantages when measuring biological analytes such as metabolites, cofactors, toxins, etc. Not only are optical signals immune to electronic interferences, but the polychromatic nature of most fluorochemical assays provides more potentially useful data about the system being studied. One of the most common difficulties normally encountered with optical biosensors is the inability to routinely recalibrate the optical and electronic components of the system throughout the life of the sensor. With this in mind, we present an optical fiber assay system for glucose based on a homogeneous singlet/singlet energy transfer assay along with the electronic instrumentation built to support the sensor system. In the sensor probe, glucose concentrations are indirectly measured from the level of fluorescence quenching caused by the homogeneous competition assay between TRITC labeled concanavalin A (receptor) and FITC labeled Dextran (ligand). The FITC signal is used to indicate glucose concentrations and the TRITC signal is used for internal calibration. Data is also presented on a protein derivatization procedure that was used to prevent aggregation of the receptor protein in solution. Also, a molecular model is described for the singlet/singlet energy transfer interactions that can occur in a model system composed of a monovalent ligand (FITC labeled papain) and a monovalent receptor (TRITC labeled concanavalin A).

Meadows, David L.; Schultz, Jerome S.

1992-04-01

99

A simple sequence repeat-based linkage map of barley.  

PubMed Central

A total of 568 new simple sequence repeat (SSR)-based markers for barley have been developed from a combination of database sequences and small insert genomic libraries enriched for a range of short simple sequence repeats. Analysis of the SSRs on 16 barley cultivars revealed variable levels of informativeness but no obvious correlation was found with SSR repeat length, motif type, or map position. Of the 568 SSRs developed, 242 were genetically mapped, 216 with 37 previously published SSRs in a single doubled-haploid population derived from the F(1) of an interspecific cross between the cultivar Lina and Hordeum spontaneum Canada Park and 26 SSRs in two other mapping populations. A total of 27 SSRs amplified multiple loci. Centromeric clustering of markers was observed in the main mapping population; however, the clustering severity was reduced in intraspecific crosses, supporting the notion that the observed marker distribution was largely a genetical effect. The mapped SSRs provide a framework for rapidly assigning chromosomal designations and polarity in future mapping programs in barley and a convenient alternative to RFLP for aligning information derived from different populations. A list of the 242 primer pairs that amplify mapped SSRs from total barley genomic DNA is presented. PMID:11102390

Ramsay, L; Macaulay, M; degli Ivanissevich, S; MacLean, K; Cardle, L; Fuller, J; Edwards, K J; Tuvesson, S; Morgante, M; Massari, A; Maestri, E; Marmiroli, N; Sjakste, T; Ganal, M; Powell, W; Waugh, R

2000-01-01

100

Quantum dot-based immunochromatographic fluorescent biosensor for biomonitoring trichloropyridinol, a biomarker of exposure to chlorpyrifos.  

PubMed

A novel and portable fluorescent sensor that integrates an immunochromatographic test strip assay (ITSA) with a quantum dot (QD) label and a test strip reader was described in this study for simple, rapid, and sensitive biomonitoring of an organophosphorus pesticide metabolite. The principle of this sensor is based on a competitive immunoreaction that was performed on an immunochromatographic test strip, where analytes compete with competitors (QD-conjugated analogs) to bind to antibodies on a test zone. Captured QDs serve as signal vehicles for fluorescent readout. In this work, 3,5,6-trichloropyridinol (TCP) is used as a model analyte to demonstrate the performance of the immunosensor. QD-TCP conjugates were synthesized and characterized with X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. Some parameters (e.g., the amount of QD-modified TCP and immunoreaction time) that govern sensitivity and reproducibility of ITSA were optimized. Under optimal conditions, the sensor has a wide dynamic range and is capable of detecting a minimum 1.0 ng/mL TCP standard analyte in 15 min. The sensor has been successfully applied for detection of TCP spiked in rat plasma with average recovery of 102.0%. Results demonstrate that this sensor provides a rapid, clinically accurate, and quantitative tool for TCP detection and shows great promise for in-field and point-of-care (POC) quantitative testing and screening for metabolite biomarkers, e.g., TCP, for humans exposed to pesticides. PMID:20507134

Zou, Zhexiang; Du, Dan; Wang, Jun; Smith, Jordan N; Timchalk, Charles; Li, Yaoqun; Lin, Yuehe

2010-06-15

101

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

102

Bispectral Photometric Stereo based on Fluorescence National Institute of Informatics  

E-print Network

natural gems and corals, to fluorescent dyes used in clothing. One of the important characteristics phenomenon oc- curring in many objects from natural gems and corals, to fluorescent dyes used for clothing), fluorescent-only image observed in the red channel (mid- dle), and reflective-component-only images observed

Tokyo, University of

103

Simple-Random-Sampling-Based Multiclass Text Classification Algorithm  

PubMed Central

Multiclass text classification (MTC) is a challenging issue and the corresponding MTC algorithms can be used in many applications. The space-time overhead of the algorithms must be concerned about the era of big data. Through the investigation of the token frequency distribution in a Chinese web document collection, this paper reexamines the power law and proposes a simple-random-sampling-based MTC (SRSMTC) algorithm. Supported by a token level memory to store labeled documents, the SRSMTC algorithm uses a text retrieval approach to solve text classification problems. The experimental results on the TanCorp data set show that SRSMTC algorithm can achieve the state-of-the-art performance at greatly reduced space-time requirements. PMID:24778587

Liu, Wuying; Wang, Lin; Yi, Mianzhu

2014-01-01

104

Simple-random-sampling-based multiclass text classification algorithm.  

PubMed

Multiclass text classification (MTC) is a challenging issue and the corresponding MTC algorithms can be used in many applications. The space-time overhead of the algorithms must be concerned about the era of big data. Through the investigation of the token frequency distribution in a Chinese web document collection, this paper reexamines the power law and proposes a simple-random-sampling-based MTC (SRSMTC) algorithm. Supported by a token level memory to store labeled documents, the SRSMTC algorithm uses a text retrieval approach to solve text classification problems. The experimental results on the TanCorp data set show that SRSMTC algorithm can achieve the state-of-the-art performance at greatly reduced space-time requirements. PMID:24778587

Liu, Wuying; Wang, Lin; Yi, Mianzhu

2014-01-01

105

A simple parallel tandem organic solar cell based on metallophthalocyanines  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

106

A simple method to improve ensemble-based ozone forecasts  

NASA Astrophysics Data System (ADS)

Forecasts from seven air quality models and ozone data collected over the eastern USA and southern Canada during July and August 2004 are used in creating a simple method to improve ensemble-based forecasts of maximum daily 1-hr and 8-hr averaged ozone concentrations. The method minimizes least-square error of ensemble forecasts by assigning weights for its members. The real-time ozone (O3) forecasts from this ensemble of models are statistically evaluated against the ozone observations collected for the AIRNow database comprising more than 350 stations. Application of this method is shown to significantly improve overall statistics (e.g., bias, root mean square error, and index of agreement) of the weighted ensemble compared to the averaged ensemble or any individual ensemble member. If a sufficient number of observations is available, we recommend that weights be calculated daily; if not, a longer training phase will still provide a positive benefit.

Pagowski, M.; Grell, G. A.; McKeen, S. A.; Dévényi, D.; Wilczak, J. M.; Bouchet, V.; Gong, W.; McHenry, J.; Peckham, S.; McQueen, J.; Moffet, R.; Tang, Y.

2005-04-01

107

Highly adaptable and sensitive protease assay based on fluorescence resonance energy transfer.  

PubMed

Proteases are widely used in analytical sciences and play a central role in several widespread diseases. Thus, there is an immense need for highly adaptable and sensitive assays for the detection and monitoring of various proteolytic enzymes. We established a simple protease fluorescence resonance energy transfer (pro-FRET) assay for the determination of protease activities, which could in principle be adapted for the detection of all proteases. As proof of principle, we demonstrated the potential of our method using trypsin and enteropeptidase in complex biological mixtures. Briefly, the assay is based on the cleavage of a FRET peptide substrate, which results in a dramatic increase of the donor fluorescence. The assay was highly sensitive and fast for both proteases. The detection limits for trypsin and enteropeptidase in Escherichia coli lysate were 100 and 10 amol, respectively. The improved sensitivity for enteropeptidase was due to the application of an enzyme cascade, which leads to signal amplification. The pro-FRET assay is highly specific as even high concentrations of other proteases did not result in significant background signals. In conclusion, this sensitive and simple assay can be performed in complex biological mixtures and can be easily adapted to act as a versatile tool for the sensitive detection of proteases. PMID:21892820

Zauner, Thomas; Berger-Hoffmann, Renate; Müller, Katrin; Hoffmann, Ralf; Zuchner, Thole

2011-10-01

108

Fluorescence-lifetime-based tomography for turbid Anand T. N. Kumar  

E-print Network

Fluorescence-lifetime-based tomography for turbid media Anand T. N. Kumar Athinoula A. Martinos of time-domain fluorescence measurements with turbid tissue. We experimentally demon- strate the advantage- sitive fluorescent probes to 3-D in vivo imaging in several-centimeter-thick turbid tissue. Let

109

Synthesis and characterization of Rhodamine based Pb 2+ selective fluorescence sensor  

Microsoft Academic Search

We have synthesized and characterized a new Rhodamine-based Pb2+ selective fluorescent sensor. The fluorescent Pb2+ sensor Rh2 was synthesized by reaction of Rhodamine B with 2-bromoethylamine followed by sodium azide in high yield. We found\\u000a that fluorescent sensor Rh2 exhibits a good selectivity toward Pb2+ over other metal ions in chloroform solution. In the absence of Pb2+, fluorescent sensor Rh2

Tielong Gao; Kyung Mi Lee; Sung Ik Yang

2009-01-01

110

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

111

Optical biopsy fiber-based fluorescence spectroscopy instrumentation  

NASA Astrophysics Data System (ADS)

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

Katz, Alvin; Ganesan, Singaravelu; Yang, Yuanlong; Tang, Gui C.; Budansky, Yury; Celmer, Edward J.; Savage, Howard E.; Schantz, Stimson P.; Alfano, Robert R.

1996-04-01

112

A Simple, Scalable, Script-based Science Processor  

NASA Technical Reports Server (NTRS)

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

Lynnes, Christopher

2004-01-01

113

Simple, Defensible Sample Sizes Based on Cost Efficiency  

PubMed Central

Summary The conventional approach of choosing sample size to provide 80% or greater power ignores the cost implications of different sample size choices. Costs, however, are often impossible for investigators and funders to ignore in actual practice. Here, we propose and justify a new approach for choosing sample size based on cost efficiency, the ratio of a study’s projected scientific and/or practical value to its total cost. By showing that a study’s projected value exhibits diminishing marginal returns as a function of increasing sample size for a wide variety of definitions of study value, we are able to develop two simple choices that can be defended as more cost efficient than any larger sample size. The first is to choose the sample size that minimizes the average cost per subject. The second is to choose sample size to minimize total cost divided by the square root of sample size. This latter method is theoretically more justifiable for innovative studies, but also performs reasonably well and has some justification in other cases. For example, if projected study value is assumed to be proportional to power at a specific alternative and total cost is a linear function of sample size, then this approach is guaranteed either to produce more than 90% power or to be more cost efficient than any sample size that does. These methods are easy to implement, based on reliable inputs, and well justified, so they should be regarded as acceptable alternatives to current conventional approaches. PMID:18482055

Bacchetti, Peter; McCulloch, Charles E.; Segal, Mark R.

2009-01-01

114

Development of an image processing support system based on fluorescent dye to prevent elderly people with dementia from wandering.  

PubMed

The wandering of elderly people with dementia is a significant behavioral problem and is a heavy burden on caregivers in residential and nursing homes. Thus, warning systems have been developed to prevent elderly people with dementia from leaving the premises. Some of these systems use radio waves. However, systems based on radio waves present several practical problems. For instance, the transmitter must be carried and may become lost; in addition, the battery of the transmitter must be changed. To solve these problems, we developed a support system that prevents elderly people with dementia from wandering. The system employs image processing technology based on fluorescent dye. The composition of the support system can be described as follows: fluorescent dye is painted in a simple shape on the clothes of an elderly person. The fluorescent color becomes visible by irradiation with a long wavelength of ultraviolet light. In the present paper, the relationship between the color of the dye and the cloth was investigated. A 3D video camera was used to acquire a 3D image and detect the simple shape. As a preliminary experiment, 3 colors (red, green and blue) of fluorescent dye were applied to cloths of 9 different colors. All fluorescent colors were detected on 6 of the cloths, but red and blue dye could not be detected on the other 3 cloths. In contrast, green dye was detectable on all 9 of the cloths. Additionally, we determined whether green dye could be detected in an actual environment. A rectangular shaped patch of green fluorescent dye was painted on the shoulder area of a subject, from the scapula to the clavicle. As a result, the green dye was detected on all 9 different colored cloths. PMID:24111431

Nishigaki, Yutaka; Tanaka, Kentaro; Kim, Juhyon; Nakajima, Kazuki

2013-01-01

115

A fluorescence method for detection of DNA and DNA methylation based on graphene oxide and restriction endonuclease HpaII.  

PubMed

DNA methylation plays an important role in many biological events and is associated with various diseases. Most traditional methods for detection of DNA methylation are based on the complex and expensive bisulfite method. In this paper, we report a novel fluorescence method to detect DNA and DNA methylation based on graphene oxide (GO) and restriction endonuclease HpaII. The skillfully designed probe DNA labeled with 5-carboxyfluorescein (FAM) and optimized GO concentration keep the probe/target DNA still adsorbed on the GO. After the cleavage action of HpaII the labeled FAM is released from the GO surface and its fluorescence recovers, which could be used to detect DNA in the linear range of 50pM-50nM with a detection limit of 43pM. DNA methylation induced by transmethylase (Mtase) or other chemical reagents prevents HpaII from recognizing and cleaving the specific site; as a result, fluorescence cannot recover. The fluorescence recovery efficiency is closely related to the DNA methylation level, which can be used to detect DNA methylation by comparing it with the fluorescence in the presence of intact target DNA. The method for detection of DNA and DNA methylation is simple, reliable and accurate. PMID:25281112

Wei, Wei; Gao, Chunyan; Xiong, Yanxiang; Zhang, Yuanjian; Liu, Songqin; Pu, Yuepu

2015-01-01

116

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

PubMed

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

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

2014-01-21

117

High power light emitting diode based setup for photobleaching fluorescent impurities  

E-print Network

High power light emitting diode based setup for photobleaching fluorescent impurities Tobias K be photobleached before final sample preparation. The instrument consists of high power light emitting diodes

Kaufman, Laura

118

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

119

Fluorescence Rise Time Measurements for High Temperature Fluorescence-Based Thermometry  

SciTech Connect

Certain ceramic-like phosphor materials exhibit bright fluorescence with a pronounced temperature dependence over a range which spans the cryogenic to 1700 C, depending on the specific phosphor. To measure temperature, a surface, for instance a turbine blade, is coated with the material. An optical system, sometimes including optical fibers, conveys stimulating light and collects the emission for analysis. Either emission intensity or decay time may indicate temperature. Previously fielded tests have involved surfaces such as blades, vanes, pistons, in-take valves, sheets of galvanneal steel, etc. The fluorescent coatings may be applied to small parts via sputtering methods or to large areas by mixture with inorganic binders. Presented here are results characterizing fluorescence rise times as a means of determining temperature from ambient to 700 C for Y{sub 2}O{sub 3}:Eu.

Allison, S.W.

2005-03-24

120

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

121

Hypochlorous acid turn-on fluorescent probe based on oxidation of diphenyl selenide.  

PubMed

A BODIPY-based fluorescent probe, HCSe, has been successfully developed for the rapid detection of hypochlorous acid based on the specific HOCl-promoted oxidation of diphenyl selenide in response to the amount of HOCl. Confocal fluorescence microscopy imaging using RAW264.7 cells showed that the new probe HCSe could be used as an effective fluorescent probe for detecting HOCl in living cells. PMID:23373559

Liu, Shi-Rong; Wu, Shu-Pao

2013-02-15

122

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

PubMed Central

Novel fluorescent chalcone-based ligands at human histamine H3 receptors (hH3R) have been designed, synthesized, and characterized. Compounds described are non-imidazole analogs of ciproxifan with a tetralone motif. Tetralones as chemical precursors and related fluorescent chalcones exhibit affinities at hH3R in the same concentration range like the reference antagonist ciproxifan (hH3R pKi value of 7.2). Fluorescence characterization of our novel ligands shows emission maxima about 570?nm for yellow fluorescent chalcones and ?600?nm for the red fluorescent derivatives. Interferences to cellular autofluorescence could be excluded. All synthesized chalcone compounds could be used to visualize hH3R proteins in stably transfected HEK-293 cells using confocal laser scanning fluorescence microscopy. These novel fluorescent ligands possess high potential to be used as pharmacological tools for hH3R visualization in different tissues. PMID:22470321

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

2012-01-01

123

A simple but highly selective and sensitive fluorescence reporter for toxic CdII ion via excimer formation  

NASA Astrophysics Data System (ADS)

High selectivity and fluorescence sensitivity of a well-recognized antiexcitotoxic and anticonvulsant drug, kynurenic acid (KA), toward CdII ion has been demonstrated by UV-vis, fluorescence, 1H NMR spectroscopy in combination with computational calculations. Upon complexation with CdII, KA exhibits a distinct excimer emission at 528 nm along with monomer emission at 402 nm. The sensing ability of drug KA toward CdII ion is distinctly different from sensing for HgII or CuII ion. KA can form dimer by intermolecular O-H⋯O hydrogen bonding between the -COOH groups. Presence of CdII metal ions promotes dimer formation in the excited state which exhibits excimer fluorescence.

Samanta, Anuva; Guchhait, Nikhil; Bhattacharya, Subhash Chandra

2014-09-01

124

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

PubMed

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

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

2014-07-24

125

Immunosensor based on fluorescence quenching matrix of the conducting polymer polypyrrole.  

PubMed

In this study, the combination of autofluorescent proteins and fluorescence quenching polymers was shown to be a design which can increase the selectivity and sensitivity of immunosensors. With this objective, the conducting polymer polypyrrole (Ppy) was used as a matrix for immobilization of proteins, which enables biological recognition of the analyte, and as a fluorescence quencher, which increases the selectivity of fluorescence-based detection. In this study, bovine leukemia virus proteins gp51 were immobilized within the Ppy matrix and formed a polymeric layer with affinity for antibodies against protein gp51 (anti-gp51). The anti-gp51 antibodies are present at high levels in the blood serum of cattle infected by bovine leukemia virus. Secondary antibodies labeled with horseradish peroxidase (HRP) were used as specific fluorescent probes for detection of a particular target, because the fluorescence of HRP was readily detectable at the required sensitivity. The Ppy was used as fluorescent background, because its fluorescence was almost undetectable when excited by near UV light at 325 nm. Moreover the Ppy quenched the fluorescence of some fluorescent agents including fluorescein-5(6)-isothiocyanate (fluorescein), rhodamine B, and HRP by almost 100% when these fluorescent agents were adsorbed on the surface of Ppy. It is predicted that Ppy-induced fluorescence quenching could be used in the design of immunosensors to increase selectivity and sensitivity. PMID:20941482

Ramanavicius, A; Ryskevic, N; Oztekin, Y; Kausaite-Minkstimiene, A; Jursenas, S; Baniukevic, J; Kirlyte, J; Bubniene, U; Ramanaviciene, A

2010-12-01

126

Determination of local high temperature excursion in an intrinsic doped fiber fluorescence-based sensor  

Microsoft Academic Search

A fluorescence-based intrinsic doped fiber temperature sensing system for determining local extremes of high temperatures has been demonstrated in this work. Data on this temperature rise are analyzed using a mathematical relationship, based on a correlation coefficient ratio scheme, to relate to the reduced fluorescence decay time information thus associated with the hot part of the fiber. In schemes incorporating

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

1998-01-01

127

Optical fiber-based fluorescent viscosity sensor Mark A. Haidekker and Walter J. Akers  

E-print Network

Optical fiber-based fluorescent viscosity sensor Mark A. Haidekker and Walter J. Akers Department bound to a fiber-optic tip without loss of viscosity sensi- tivity. The optical fiber itself may be used to molecular rotors in solution. An optical fiber-based fluorescent vis- cosity sensor may be used in real

Theodorakis, Emmanuel

128

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

PubMed

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

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

2014-05-01

129

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

NASA Astrophysics Data System (ADS)

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

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

2006-02-01

130

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

131

Turn-on fluorescent dopamine sensing based on in situ formation of visible light emitting polydopamine nanoparticles.  

PubMed

Dopamine is the principle biomarker for diseases such as schizophrenia, Huntington's, and Parkinson's, and the need is urgent for rapid and sensitive detection methods for diagnosis and monitoring of such diseases. In this Article, we report a turn-on fluorescent method for rapid dopamine sensing which is based on monitoring the intrinsic fluorescence of in situ synthesized polydopamine nanoparticles. The assay uses only a common base and an acid, NaOH and HCl to initiate and stop the polymerization reaction, respectively, which makes the assay extremely simple and low cost. First, we studied the in situ optical properties of polydopamine nanoparticles, for the first time, which formed under different alkaline conditions in order to determine optimum experimental parameters. Then, under optimized conditions we demonstrated high sensitivity (40 nM) and excellent selectivity of the assay. With its good analytical figures of merit, the described method is very promising for detection of dopamine related diseases. PMID:24803112

Yildirim, Adem; Bayindir, Mehmet

2014-06-01

132

Aptamer-based cell imaging reagents capable of fluorescence switching.  

PubMed

We describe an aptamer-conjugated polydiacetylene imaging probe (ACP) that shows highly specific fluorescence switching upon binding to epithelial cancer cells that overexpress the tumor biomarker protein EpCAM (epithelial cell adhesion molecule) on their surface. PMID:25182171

Jung, Yun Kyung; Woo, Min-Ah; Soh, H Tom; Park, Hyun Gyu

2014-09-18

133

A cell-based functional assay using a green fluorescent protein-based calcium indicator dCys-GCaMP.  

PubMed

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; Liu, Jay

2014-08-01

134

Development of a simple radiation system based on synthetic mats  

NASA Astrophysics Data System (ADS)

Possibilities to use the physical effect of passive radiation cooling economically for space cooling in arid areas were investigated. Development of emitter layer configurations (coatings); computer models for optimization of the heat exchangers; and determination of design features for practical realization were studied. Practical tests prove that an economically feasible approach is possible with simple components.

Abel, K.; Hampel, A.; Kerber, W.; Percornik, D.; Sattler, K.

1985-11-01

135

A fluorescent biosensor based on carbon dots-labeled oligodeoxyribonucleotide and graphene oxide for mercury (II) detection.  

PubMed

As the newest two members of the carbon materials family, carbon dots (CDs) and graphene oxide (GO) possess many excellent optical properties resulting in a wide range of applications. In this work, we successfully synthesized CDs with a high-quantum-yield, and labeled them on oligodeoxyribonucleotide (ODN). The fluorescence of resultant CDs-labeled oligodeoxyribonucleotide (ODN-CDs) was quenched by GO via fluorescence resonance energy transfer. In the presence of Hg(2+), the fluorescence was recovered by the release of ODN-CDs from GO due to the formation of T-Hg(2+)-T duplex. In the light of this theory, we designed a simple, highly sensitive and selective fluorometric Hg(2+) sensor based on CDs-labeled oligodeoxyribonucleotide and GO without complicated, costly and time-consuming operations. Under the optimal conditions, a linear relationship was obtained between relative fluorescence intensity and the concentration of Hg(2+) in the range of 5-200 nM (R(2)=0.974). The present GO-based sensor system is highly selective toward Hg(2+) over a wide range of metal ions and has a detection limit of 2.6 nM. This method is reliable, and has been successfully applied for the detection of Hg(2+) in practical samples. PMID:25137567

Cui, Xin; Zhu, Lei; Wu, Jing; Hou, Yu; Wang, Peiyao; Wang, Zhenni; Yang, Mei

2015-01-15

136

Simple and inexpensive immunoassay-based diagnostic tests  

Microsoft Academic Search

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

Henna Päkkilä; Tero Soukka

2011-01-01

137

MIDP-based Realization of a Simple Phone Contact Book  

NASA Astrophysics Data System (ADS)

This paper describes the architecture of J2ME and MIDP specification, use the Java language to implement a simple cell phone contact book system, to complete a contact to add, delete, modify, query functions. Different from existing phone contacts, it can run any MIDP-enabled mobile phones, avoid the question of using tool software into and out of phone contact book after user change phone.

Niu, Yan; Xia, Heng; Huan, Lele

138

A SIMPLE based discontinuous Galerkin solver for steady incompressible flows  

NASA Astrophysics Data System (ADS)

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

Klein, Benedikt; Kummer, Florian; Oberlack, Martin

2013-03-01

139

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

140

Protein-based fluorescent metal nanoclusters for small molecular drug screening.  

PubMed

A facile drug screening method based on synthesis of fluorescent gold nanoclusters inside albumin proteins loaded with small molecular drugs and comparing the relative fluorescence intensities of the resultant gold nanoclusters has been developed and successfully applied for the quantitative measurement of drug-protein binding constants. PMID:25253537

Yu, Yong; New, Siu Yee; Xie, Jianping; Su, Xiaodi; Tan, Yen Nee

2014-10-14

141

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

142

Fluorescence correlation spectroscopy based upon two-photon excitation  

NASA Astrophysics Data System (ADS)

Fluorescence correlation spectroscopy (FCS) is a powerful tool for measurement of biological dynamic processes. In this studying, a two-photon excitation fluorescence correlation spectroscopy (TP-FCS) system was set up depending on a part of optical block and detector of the multi-photon excitation fluorescence microscope (MPLFM). The phenomenon "photon-burst" was observed from the TP-FCS system. Meanwhile, the diffusion coefficient of rhodamine B molecule in sucrose aqueous solution was calculated. It was proved that TP-FCS is especially suited for integration into MPEFM accordingly to yield a hybride-technology with the peculiarities of the individual technique and the advantage of mutual synergistic effects. The fusion of both techniques seems to be reasonable and desirable to reduce costs.

Liu, Yafeng; Chen, Tongsheng; Luo, Qingming

2003-12-01

143

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

PubMed Central

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

Honda, Yuki; Kirimura, Kohtaro

2013-01-01

144

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

145

PCA based polarized fluorescence study for detecting human cervical dysplasia  

NASA Astrophysics Data System (ADS)

The two highest principal components of fluorescence spectra in visible region obtained, using Xenon lamp as an excitation source of normal and dysplastic human cervical tissues are analyzed using scatter plots and probability density functions. These yield significant differences between the tissue types.

Gharekhan, Anita H.; Devi, Seema; Jagtap, Jaidip; Panigrahi, Prasanta K.; Pradhan, Asima

2013-02-01

146

Competitive Quenching Fluorescence Immunoassay for Chlorophenols Based on  

E-print Network

. The detectability achieved is sufficient for occupational exposure risk assessment. Fluorescent detection methods was similar to that observed in the buffer. A LOD of 1.6 µg L-1, with a dynamic range between 4 and 149.5 µg L

Hammock, Bruce D.

147

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

148

Thermal lens technique to evaluate the fluorescence quantum yield of a schiff base  

NASA Astrophysics Data System (ADS)

The fluorescence spectrum of the schiff base obtained from salicylaldehyde and 2-aminophenol is studied using an argon-ion laser as the excitation source and its fluorescence quantum yield (Qf) is determined using a thermal lens method. This is a nondestructive technique that gives the absolute value of Qf without the need for a fluorescence standard. The quantum-yield values are calculated for various concentrations of the solution in chloroform and also for various excitation wavelengths. The value of Qf is relatively high, and is concentration dependent. The maximum value of Qf obtained is nearly 0.78. The high value of the fluorescence quantum yield will render the schiff base useful as a fluorescent marker for biological applications. Photostability and gain studies will assess its suitability as a laser dye.

Santhi, A.; Kala, U. L.; Nedumpara, R. J.; Kurian, A.; Kurup, M. R. P.; Radhakrishnan, P.; Nampoori, V. P. N.

2004-09-01

149

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

SciTech Connect

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

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

1994-09-01

150

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

PubMed

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

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

2013-12-15

151

Heats of sublimation of nitramines based on simple parameters.  

PubMed

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

Keshavarz, Mohammad Hossein; Yousefi, Mohammad Hassan

2008-04-15

152

2-Aminopurine as a fluorescent probe for DNA base flipping by methyltransferases.  

PubMed Central

DNA base flipping, which was first observed for the C5-cytosine DNA methyltransferase M. Hha I, results in a complete removal of the stacking interactions between the target base and its neighbouring bases. We have investigated whether duplex oligodeoxynucleotides containing the fluorescent base analogue 2-aminopurine can be used to sense DNA base flipping. Using M. Hha I as a paradigm for a base flipping enzyme, we find that the fluorescence intensity of duplex oligodeoxynucleotides containing 2-aminopurine at the target site is dramatically enhanced (54-fold) in the presence of M. Hha I. Duplex oligodeoxynucleotides containing 2-aminopurine adjacent to the target cytosine show little fluorescence increase upon addition of M. Hha I. These results clearly demonstrate that duplex oligodeoxynucleotides containing 2-aminopurine at the target site can serve as fluorescence probes for base flipping. Another enzyme hypothesized to use a base flipping mechanism is the N6-adenine DNA methyltransferase M. Taq I. Addition of M. Taq I to duplex oligodeoxynucleotides bearing 2-aminopurine at the target position, also results in a strongly enhanced fluorescence (13-fold), whereas addition to duplex oligodeoxynucleotides containing 2-aminopurine at the 3'- or 5'-neighbouring position leads only to small fluorescence increases. These results give the first experimental evidence that the adenine-specific DNA methyltransferase M. Taq I also flips its target base. PMID:9461471

Holz, B; Klimasauskas, S; Serva, S; Weinhold, E

1998-01-01

153

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

154

Semi-Permeable Microcapsules for Use in Fluorescence-Based Glucose Sensing  

E-print Network

Due to the pain associated with conventional blood sugar monitoring techniques and the rising prevalence of diabetes, the development of noninvasive glucose sensing techniques is desirable. Towards this aim, implantable fluorescence-based glucose...

Joachim, Elizabeth G.

2011-08-08

155

Fluorescence-based video profile beam diagnostics: Theory and experience  

SciTech Connect

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

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

1994-05-01

156

Fluorescence-based video profile beam diagnostics: Theory and experience  

SciTech Connect

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

Sandoval, D.P.; Garcia, R.C.; Gilpatrick, J.D.; Shinas, M.A.; Wright, R.; Yuan, V.; Zander, M.E. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

1994-10-10

157

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

158

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

159

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

160

Highly Sensitive Fluorescent Probe for Clenbuterol Hydrochloride Detection Based on its Catalytic Oxidation of Eosine Y by NaIO4.  

PubMed

A highly sensitive fluorescent probe for clenbuterol hydrochloride (CLB) detection has been first designed based on its catalytic effect on NaIO4 oxidating eosine Y (R). And this environment-friendly, simple, rapid, selective and sensitive fluorescent probe has been utilized to detect CLB in the practical samples with the results consisting with those obtained by GC/MS. The structures of R and CLB were characterized by infrared spectra. The mechanism of the proposed assay for the detection of CLB was also discussed. PMID:25155629

Liu, Jiaming; Liu, Zhen-Bo; Huang, Qitong; Lin, Chang-Qing; Lin, Xiaofeng

2014-09-01

161

A fluorescence-based assay for measuring the redox potential of 5-lipoxygenase inhibitors.  

PubMed

The activities and side effects of 5-lipoxygenase (5-LO) inhibitors can be predicted by identifying their redox mechanisms. In this study, we developed a fluorescence-based method to measure the redox potential of 5-LO inhibitors and compared it to the conventional, absorbance-based method. After the pseudo-peroxidase reaction, the amount of remaining lipid peroxide was quantified using the H2DCFDA (2',7'-dichlorodihydrofluorescein diacetate) fluorescence dye. Our method showed large signal windows and provided comparable redox potential values. Importantly, the redox mechanisms of known inhibitors were accurately measured with the fluorescence assay, whereas the conventional, absorbance-based method showed contradictory results. Our findings suggest that our developed method is a better alternative for classifying the redox potential of 5-LO inhibitors, and the fluorescence assay can be effectively used to study the mechanisms of action that are related to redox cycling. PMID:24498359

Lee, Sangchul; Park, Youngsam; Kim, Junghwan; Han, Sung-Jun

2014-01-01

162

Communications A simple colorimetric sensing array based on four  

E-print Network

on the basis of Brønsted basicity; and finally 4) highly solvatochromic dyes (for example, Reich- ardts ET30 employed arrays of sensors based either on adsorption into a set of polymers or on oxidations at a set on the basis of the chemical properties of analytes. Four families of chemically responsive dyes were

Suslick, Kenneth S.

163

Determination of L-Argininamide Based on Water-Soluble Fluorescent Conjugated Polymer-Aptamer  

PubMed Central

Water-soluble fluorescent conjugated polymer is a promising material which could be used as an optical platform in highly sensitive molecular sensors. In this paper, a simple label-free DNA sensor, which consisted of a poly(3-alkoxy-4-methylthiophene) and an aptamer, was used to detect L-argininamide (L-Arm). Due to the specific binding reaction between L-Arm and its aptamer, the proposed method can easily determinate the L-Arm through the recovery of fluorescence without any modification. Other ions or similar molecules had little effect on the detection. Moreover, there was a linear relationship between fluorescence intensity and the concentration of L-Arm. The detection limit of L-Arm was as low as 4.7?nM. PMID:24027654

Guan, Hongliang; He, Zhike

2013-01-01

164

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

165

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

166

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

167

Simple method of determination of iodide at microgram/L level in potable water with preliminary preconcentration by energy dispersive X-ray fluorescence spectrometry.  

PubMed

A simple method for iodide determination in potable water with preliminary preconcentration has been worked out. Iodide was precipitated as palladium (II) iodide on elemental palladium as a carrier, which was obtained by reduction of Pd(II) with sodium thiosulfate. Ammonium chloropalladite was used as a reagent. The volume of water taken for analysis was between 100 and 500 cm3. The precipitate was filtered through a membrane filter, air-dried and directly analyzed by the energy-dispersive x-ray fluorescence (EDXRF) method. 241Am radioisotope was used as a source of exciting radiation. The precision of the method was 7% for iodide mass per filter equal to 2 micrograms. The detection limit amounted to 0.45 microgram of iodide per filter. PMID:1822324

Holynska, B; Ostachowicz, B; Wegrzynek, D

1991-03-01

168

Micro-optical lens array for fluorescence detection in droplet-based microfluidics.  

PubMed

We demonstrate the design and integration of droplet-based microfluidic devices with microoptical element arrays for enhanced detection of fluorescent signals. We show that the integration of microlenses and mirror surfaces in these devices results in an 8-fold increase in the fluorescence signal and in improved spatial resolution. Using an array of microlenses, massively parallel detection of droplets containing fluorescent dyes was achieved, leading to detection throughputs of about 2000 droplets per second and per lens, parallelized over 625 measurement points. PMID:23455606

Lim, Jiseok; Gruner, Philipp; Konrad, Manfred; Baret, Jean-Christophe

2013-04-21

169

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

PubMed

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

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

2014-06-21

170

Molecular self assembly on optical fiber-based fluorescence sensor  

NASA Astrophysics Data System (ADS)

We discuss the molecular self-assembly on optical fibers in which a novel method for protein attachment to the sensing tip of the fiber is used. Our objective is to assemble a conjugated polythiophene copolymer as an attachment vehicle. Subsequent attachment of the photodynamic phycobiliprotein serves as the fluorescence probe element. Following our earlier experiments from Langmuir-Blodgett deposition of these polymeric materials as thin films on glass substrates, we extended the technique to optical fibers. First, the bare fiber surface is silanized with a C18 silane compound. The copolymer (3-undecylthiophene-co-3- methanolthiophene, biotinylated at the methanol moiety) assembly on the fiber is carried out presumable through van der Waals interactions between the hydrophobic fiber surface and the undecyl alkyl chains on the polymer backbone. A conjugated Str-PE (streptavidin covalently attached to phycoerythrin) complex is then attached to the copolymer via the conventional biotin-streptavidin interaction. The conjugated polymer not only supports the protein but, in principle, may help to transduce the signal generated by phycoerythrin to the fiber. Our results from fluorescence intensity measurements proved the efficacy of this system. An improved methodology is also sought to more strongly attach the conjugated copolymer to the fiber surface, and a covalent scheme is developed to polymerize and biotinylate polythiophene in situ on the fiber surface.

Ayyagari, Madhu S. R.; Gao, Harry H.; Bihari, Bipin; Chittibabu, Kethinni G.; Kumar, Jayant; Marx, Kenneth A.; Kaplan, David L.; Tripathy, Sukant K.

1994-03-01

171

Computed tomography-based spectral imaging for fluorescence microscopy.  

PubMed Central

The computed tomography imaging spectrometer (CTIS) is a non-scanning instrument capable of simultaneously acquiring full spectral information (450-750 nm) from every position element within its field of view (75 microm x 75 microm). The current spatial and spectral sampling intervals of the spectrometer are 1.0 microm and 10 nm, respectively. This level of resolution is adequate to resolve signal responses from multiple fluorescence probes located within individual cells or different locations within the same cell. Spectral imaging results are presented from the CTIS combined with a commercial inverted fluorescence microscope. Results demonstrate the capability of the CTIS to monitor the spatiotemporal evolution of pH in rat insulinoma cells loaded with SNARF-1. The ability to analyze full spectral information for two-dimensional (x, y) images allows precise evaluation of heterogeneous physiological responses within cell populations. Due to low signal levels, integration times up to 2 s were required. However, reasonable modifications to the instrument design will provide higher system transmission efficiency with increased temporal and spatial resolution. Specifically, a custom optical design including the use of a larger format detector array is under development for a second-generation system. PMID:11159465

Ford, B K; Volin, C E; Murphy, S M; Lynch, R M; Descour, M R

2001-01-01

172

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

PubMed

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

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

2012-05-01

173

Determination of thiabendazole residues in citrus fruits using a Multicommuted fluorescence-based optosensor  

Microsoft Academic Search

In this work, a method based on the combination of a multi-commuted flow system and solid-surface fluorescence spectroscopy has been developed and validated for the determination of thiabendazole residues in citrus fruits. The flow system was designed using three-way solenoid valves, controlled by Java-written home-made software, for independent automated manipulation of solutions. The native fluorescence signal of thiabendazole (using C18

Juan F. García-Reyes; Eulogio J. Llorent-Martínez; Pilar Ortega-Barrales; Antonio Molina-Díaz

2006-01-01

174

A fluorescence ratiometric chemosensor for Fe³? based on TBET and its application in living cells.  

PubMed

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

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

2014-10-01

175

Single fluorescent protein-based Ca2+ sensors with increased dynamic range  

Microsoft Academic Search

BACKGROUND: Genetically encoded sensors developed on the basis of green fluorescent protein (GFP)-like proteins are becoming more and more popular instruments for monitoring cellular analytes and enzyme activities in living cells and transgenic organisms. In particular, a number of Ca2+ sensors have been developed, either based on FRET (Fluorescence Resonance Energy Transfer) changes between two GFP-mutants or on the change

Ekaterina A Souslova; Vsevolod V Belousov; John G Lock; Staffan Strömblad; Sergey Kasparov; Alexey P Bolshakov; Vsevolod G Pinelis; Yulii A Labas; Sergey Lukyanov; Lorenz M Mayr; Dmitriy M Chudakov

2007-01-01

176

Fluorescent sensor based on a novel conjugated polyfluorene derivative  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

177

Fluorescence-based optrodes for alkali ions based on the use of ion carriers and lipophilic acid/base indicators  

NASA Astrophysics Data System (ADS)

We present fluorosensors for potassium calcium and ammonium based on the use of ion carriers and a highly fluorescent lipophilic proton carrier. Fluorescent potassium-sensitive membranes have been prepared by dissolving chemically modified Nile Blue and valinomycin in a pvc/plasticizer mixture. Valinomycin being a highly selective potassium carrier binds potassium ion and carries it into the membrane. Simultaneously in order to maintain electro-neutrality of the membrane a proton dissociates from the proton carrier (Nile Blue) dissolved in the pvc membrane and diffuses into the aqueous phase. The dissociation of the protonated amino group of Nile Blue causes its color to change from blue to red. Depending on the choice of the excitation wavelength both the decrease in the fluorescence of the blue species and the increase in the fluorescence of the red species can be monitored. The sensor fully reversibly responds to potassium over the 100 uM to 100 mM concentration range. By replacing valinomycin by carriers for ammonium and calcium ion the respective sensors are obtained. It also is found that the addition of hydroxylic plasticizers to the membrane material considerably accelerates the response time in both directions. While this kind of sensor suffers from cross sensitivity toward pH it has the advantage of full solid-state compatibility (LEDs or diode lasers may be used as light sources). Also because only one kind of fluorophore can be used in almost all kinds

He, Huarui; Wolfbeis, Otto S.

1991-03-01

178

A ratiometric fluorescent probe for hydrophobic proteins in aqueous solution based on aggregation-induced emission.  

PubMed

A novel fluorescent probe 1 is reported here with ratiometric response to hydrophobic proteins (casein) or proteins with hydrophobic pockets (BSA, HSA) through hydrophobic interaction. Probe 1 underwent deprotonation in aqueous solution at pH 7.4 and emitted blue fluorescence at 436 nm. Upon the addition of BSA, HSA or casein, the aggregation-induced emission fluorescence of 1 at 518 nm was turned on. The fluorescence intensity ratio, I518/I436 was linearly related to the concentrations of these proteins. The detection limits for BSA, HSA and casein based on IUPAC (CDL = 3Sb m(-1)) were 16.2 ?g mL(-1), 10.5 ?g mL(-1) and 5.7 ?g mL(-1), respectively. PMID:23435163

Peng, Lu; Wei, Ruirui; Li, Kai; Zhou, Zhaojuan; Song, Panshu; Tong, Aijun

2013-04-01

179

Fluorescent chemosensors for anions and contact ion pairs with a cavity-based selectivity.  

PubMed

The association of a concave macrocyclic compound to one or multiple fluorophores is an appealing strategy for the design of chemosensors. Indeed, as with biological systems, a cavity-based selectivity can be expected with such fluorescent receptors. Examples of calix[6]arene-based systems using this strategy are rare in the literature, and to our knowledge, no examples of fluorescent receptors that can bind organic contact ion pairs have been reported. This report describes the straightforward synthesis of fluorescent calix[6]arene-based receptors 4a and 4b bearing three pyrenyl subunits and the study of their binding properties toward anions and ammonium salts using different spectroscopies. It was found that receptor 4a exhibits a remarkable selectivity for the sulfate anion in DMSO, enabling its selective sensing by fluorescence spectroscopy. In CDCl3, the receptor is able to bind ammonium ions efficiently only in association with the sulfate anion. Interestingly, this cooperative binding of ammonium sulfate salts was also evidenced in a protic environment. Finally, a cavity-based selectivity in terms of size and shape of the guest was observed with both receptors 4a and 4b, opening interesting perspectives on the elaboration of fluorescent cavity-based systems for the selective sensing of biologically relevant ammonium salts such as neurotransmitters. PMID:24931570

Brunetti, Emilio; Picron, Jean-François; Flidrova, Karolina; Bruylants, Gilles; Bartik, Kristin; Jabin, Ivan

2014-07-01

180

Static hyperspectral fluorescence imaging of viscous materials based on a linear variable filter spectrometer.  

PubMed

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

181

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

182

Pyrrole-Based Anion Sensors, Part II: Fluorescence, Luminescence, and Electrochemical Sensors  

NASA Astrophysics Data System (ADS)

This review focuses on fluorescence and luminescence-based sensors as well as electrochemical sensors based on the pyrrole moieties. The fluorescence sensors include porphyrins and expanded porphyrins such as sapphyrins, calixpyrroles with covalently attached fluorophore moieties, and are - together with the colorimetric sensors - the largest growing group of pyrrole-based sensors. Similarly, the electrochemical sensors comprising pyrrole moieties are also becoming popular. They include calixpyrrole, porphyrin, and calixphyrin receptors combined with metallocene, as well as dipyrrolylquinoxalines and others. While the electrochemical signal transduction is at times difficult to interpret, they hold a promise for the development of sensitive ion-selective electrodes (ISEs) and other devices in the future.

Anzenbacher, Pavel

183

Structural dynamics of DNA sensed by fluorescence from chemically modified bases  

NASA Astrophysics Data System (ADS)

The dynamics of self-complementary DNA decamers containing chemically-modified recognition sequences of the Eco RI endonuclease have been investigated by temperature-dependent picosecond time-resolved fluorescence spectroscopy. The unmodified decamer, d[CTGAATTCAG], as well as the decamer with 2-aminopurine (2AP) replacing adenine in position 5, have been shown to be B-type duplexes by 2D NMR and molecular dynamics (MD) simulations. Fluorescence anisotropy decay and MD of the 2AP-containing decamer show rapid motion of the base on timescales of 10-11 to 10-10 s. The multi-exponential fluorescence decay of the fluorescence and its temperature dependence, together with the 10-ns singleexponential decay of the isolated 2AP base, suggest that the 2AP base exists in 4 or more conformational states. All of these states appear to interconvert, but only two on the timescale of the fluorescence decay. The decamer with 1-((beta)-D-2'-deoxyribosyl)-2-pyrimidinone (dK) replacing dC in position 8 is a duplex which melts at about 21° C and shows multi-exponential fluorescence decay. Fluorescence is dominated, however, by a temperature-dependent 150-200 ps decay component accounting for >90% of the decay process. The unnormalized amplitude of this component decreases with decreasing temperature, reflecting hypochromism of dK as it stacks with its neighbors. In contrast with the other two modified bases, the isolated dK base has an extremely short fluorescence lifetime in aqueous solution, about 250 ps. The decamer with the 5-methyl derivative of dK (dS) placed in position 7 appears to be single-stranded above 10° C. Fluorescence from this decamer is thermodynamically and kinetically simpler than that from the duplexes. The decay time of the isolated d5 base is about 4.0 ns, while the decamer shows a temperature-independent 4.0 +/- 0.1 ns and shorter-lived, temperature-dependent decay components. Analysis of the data shows that completely unstacked (solvent-exposed) and partially stacked states exist. The completely unstacked state is a small component at all observed temperatures.

Nordlund, Thomas M.; Wu, Pengguang; Andersson, Stig I.; Nilsson, Lennart; Rigler, Rudolf; Graslund, Astrid; McLaughlin, Lawrence W.; Gildea, Brian

1990-05-01

184

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

185

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

186

Fluorescent probes for Al(III) and Cr(III) based on a photochromic diarylethene bearing a fluorescent rhodamine unit  

Microsoft Academic Search

A sensitive and selective “turn-on” fluorescent probe (compound 1O) was prepared by combining a photochromic diarylethene with a fluorescent rhodamine unit. This compound displays a favorable\\u000a photochromism on alternating irradiation with UV\\/Vis light. Upon addition of Al(III) or Cr(III) to the probe, its color changes\\u000a from colorless to pink, and its fluorescence is markedly enhanced. The probe displays excellent sensitivity

Weijun Liu; Shouzhi Pu; Duohua Jiang; Shiqiang Cui; Gang Liu; Congbin Fan

187

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

188

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

PubMed

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

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

2011-06-01

189

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

190

Chemical biology-based approaches on fluorescent labeling of proteins in live cells.  

PubMed

Recently, significant advances have been made in live cell imaging owing to the rapid development of selective labeling of proteins in vivo. Green fluorescent protein (GFP) was the first example of fluorescent reporters genetically introduced to protein of interest (POI). While GFP and various types of engineered fluorescent proteins (FPs) have been actively used for live cell imaging for many years, the size and the limited windows of fluorescent spectra of GFP and its variants set limits on possible applications. In order to complement FP-based labeling methods, alternative approaches that allow incorporation of synthetic fluorescent probes to target POIs were developed. Synthetic fluorescent probes are smaller than fluorescent proteins, often have improved photochemical properties, and offer a larger variety of colors. These synthetic probes can be introduced to POIs selectively by numerous approaches that can be largely categorized into chemical recognition-based labeling, which utilizes metal-chelating peptide tags and fluorophore-carrying metal complexes, and biological recognition-based labeling, such as (1) specific non-covalent binding between an enzyme tag and its fluorophore-carrying substrate, (2) self-modification of protein tags using substrate variants conjugated to fluorophores, (3) enzymatic reaction to generate a covalent binding between a small molecule substrate and a peptide tag, and (4) split-intein-based C-terminal labeling of target proteins. The chemical recognition-based labeling reaction often suffers from compromised selectivity of metal-ligand interaction in the cytosolic environment, consequently producing high background signals. Use of protein-substrate interactions or enzyme-mediated reactions generally shows improved specificity but each method has its limitations. Some examples are the presence of large linker protein, restriction on the choice of introducible probes due to the substrate specificity of enzymes, and competitive reaction mediated by an endogenous analogue of the introduced protein tag. These limitations have been addressed, in part, by the split-intein-based labeling approach, which introduces fluorescent probes with a minimal size (~4 amino acids) peptide tag. In this review, the advantages and the limitations of each labeling method are discussed. PMID:23318293

Jung, Deokho; Min, Kyoungmi; Jung, Juyeon; Jang, Wonhee; Kwon, Youngeun

2013-05-01

191

A simple agent-based social impact theory model of student STEM selection  

Microsoft Academic Search

There is a growing body of knowledge describing the economic and social challenge faced by the United States because of the small (14%) and decreasing number of students pursuing Science, Technology, Engineering, and Mathematics (STEM) majors. We propose a simple two-period, agent-based simulation based on social impact theory to predict the % yield of STEM majors. The model indicates that

Theodore T. Allen; Nixon Davis

2010-01-01

192

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

E-print Network

the nature of obtaining public keys by constructing a one-to-one mapping between identities and public keysSimple Identity-Based Cryptography with Mediated RSA Xuhua Ding and Gene Tsudik Department. Identity-based public key encryption facilitates easy introduction of public key cryptography by allowing

Ding, Xuhua

193

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 structures. In this work we propose a minimal individual-based model capable of repro- ducing a large number only three main processes: birth (binary fission), death (or detachment) and surface migration

Paris-Sud XI, Université de

194

When is it okay to lie? A simple model of contraditcion in agent-based dialogues  

E-print Network

When is it okay to lie? A simple model of contraditcion in agent-based dialogues Elizabeth Sklar1 parsons@sci.brooklyn.cuny.edu Abstract. When is it okay to lie? And what constitutes a lie, anyway? This paper examines the notion of lying in agent-based systems, focusing on dialogues and situations where

Sklar, Elizabeth

195

Flavin Mononucleotide-Based Fluorescent Proteins Function in Mammalian Cells without Oxygen Requirement  

PubMed Central

Usage of the enhanced green fluorescent protein (eGFP) in living mammalian cells is limited to aerobic conditions due to requirement of oxygen during chromophore formation. Since many diseases or disease models are associated with acute or chronic hypoxia, eGFP-labeling of structures of interest in experimental studies might be unreliable leading to biased results. Thus, a chromophore yielding a stable fluorescence under hypoxic conditions is desirable. The fluorescence of flavin mononucleotide (FMN)-based fluorescent proteins (FbFPs) does not require molecular oxygen. Recently, the advantages of FbFPs for several bacterial strains and yeasts were described, specifically, their usage as a real time fluorescence marker in bacterial expression studies and their ability of chromophore formation under anaerobic conditions. Our objective was to verify if FbFPs also function in mammalian cells in order to potentially broaden the repertoire of chromophores with ones that can reliably be used in mammalian studies under hypoxic conditions. In the present study, we demonstrate for the first time, that FbFPs can be expressed in different mammalian cells, among them murine neural stem cells during proliferative and differentiated stages. Fluorescence intensities were comparable to eGFP. In contrast to eGFP, the FbFP fluorescence did not decrease when cells were exposed to defined hypoxic conditions neither in proliferating nor in differentiated cells. Thus, FbFPs can be regarded as an alternative to eGFP in studies that target cellular structures which are exposed to hypoxic conditions. PMID:22984451

Walter, Janine; Hausmann, Sascha; Drepper, Thomas; Puls, Michael; Eggert, Thorsten; Dihne, Marcel

2012-01-01

196

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

197

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

198

Near-Infrared Fluorescence Lifetime Assay for Serum Glucose Based on Allophycocyanin-Labeled  

E-print Network

. Glycemic sensing al- lows the diabetic patient to adjust insulin and food to achieve optimal metabolic tissue (3­7). The main disadvantages of these have been drift and suppressed responses in vivo (8). A fluorescence glucose assay based on the plant lec- tin concanavalin A (con A)2 competitively binding glu- cose

Strathclyde, University of

199

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 as emitters will be present. The TPE derivatives show aggregation-induced emission (AIE) characteristics, i emitters also exhibit good thermal stability, and thus good device stability may be expected. Further

200

Noninvasive optical imaging of cysteine protease activity using fluorescently quenched activity-based probes  

E-print Network

generated a series of quenched near-infrared fluorescent activity-based probes (qNIRF-ABPs) that covalently, whole-body imaging allowed direct monitoring of cathepsin activity. Importantly, the permanent nature and to correlate their activity with whole-body images. Finally, we demonstrate that these probes can be used

Bogyo, Matthew

201

A new principle photosynthesis capacity biosensor based on quantitative measurement of delayed fluorescence in vivo  

Microsoft Academic Search

Delayed fluorescence (DF) is an excellent marker for evaluating plant photosynthesis. Compared with common methods for measuring the photosynthesis rate based on consumption of CO2, DF technique can quantify the plant photosynthesis capacity more accurately and faster under its physiological status with less interference from the environment. We previously reported a method for measuring photosynthesis using DF of chloroplast [Wang,

Junsheng Wang; Da Xing; Lingrui Zhang; Li Jia

2007-01-01

202

Thiourea-based fluorescent chemosensors for aqueous metal ion detection and cellular imaging.  

PubMed

We describe three significant advances in the use of thioureas as reporting elements for metal-responsive fluorescent chemosensors. First, on the basis of the crystal structure of a chemosensor analogue, we provide a deeper understanding of the details of the thiourea coordination environment. Second, we describe a new generation of chemosensors with higher affinities for Zn(2+) and Cd(2+) than were observed for earlier probes, expanding the scope of this type of probe beyond Hg(2+) detection. Third, we show that a thiourea-based chemosensor can be employed for fluorescence microscopy imaging of Hg(2+) ion concentrations in living mammalian cells. PMID:24957917

Vonlanthen, Mireille; Connelly, Colleen M; Deiters, Alexander; Linden, Anthony; Finney, Nathaniel S

2014-07-01

203

Specific detection of Vibrio parahaemolyticus by fluorescence quenching immunoassay based on quantum dots.  

PubMed

In this study, anti-Vibrio parahaemolyticus polyclonal and monoclonal antibodies were prepared through intradermal injection immune and lymphocyte hybridoma technique respectively. CdTe quantum dots (QDs) were synthesized at pH 9.3, 98 °C for 1 h with stabilizer of 2.7:1. The fluorescence intensity was 586.499, and the yield was 62.43%. QD probes were successfully prepared under the optimized conditions of pH 7.4, 37 °C for 1 h, 250 ?L of 50 mg/mL EDC?·?HCl, 150 ?L of 4 mg/mL NHS, buffer system of Na2HPO4-citric acid, and 8 ?L of 2.48 mg/mL polyclonal antibodies. As gold nanoparticles could quench fluorescence of quantum dots, the concentration of V. parahaemolyticus could be detected through measuring the reduction of fluorescence intensity in immune sandwich reaction composed of quantum dot probe, gold-labeled antibody, and the sample. For pure culture, fluorescence intensity of the system was proportional with logarithm concentration of antigen, and the correlation coefficient was 99.764%. The fluorescence quenching immunoassay based on quantum dots is established for the first time to detect Vibrio parahaemolyticus. This method may be used as rapid testing procedure due to its high simplicity and sensitivity. PMID:24756606

Wang, Ling; Zhang, Junxian; Bai, Haili; Li, Xuan; Lv, Pintian; Guo, Ailing

2014-07-01

204

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

205

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

206

Evaluation of acridine in Nafion as a fluorescence-lifetime-based pH sensor.  

PubMed

We report a novel fluorescence-lifetime-based pH sensing method that utilizes acridine incorporated into Nafion (AcNaf) as the fluorescent indicator. The AcNaf sensor is excited using a 380 nm light emitting diode (LED) and the fluorescence lifetimes are measured at 450 and 500 nm. The fluorescence behavior of acridine as a function of pH in aqueous phosphate buffers and incorporated into the Nafion membrane has been investigated. The results show that incorporating acridine into Nafion changes the apparent ground-state pKa from -5.45 to -9, while the apparent excited-state pKa* is only slightly changed (approximately 9.4 in 0.1 M phosphate buffer). The AcNaf film shows a good pH response with a change in average lifetime of approximately 19 ns (at an emission wavelength of 450 nm) over the pH 8 to 10 range. We also show that excited-state protonation does not occur in the AcNaf sensor film and that chloride quenching cannot occur because of the permselective nature of Nafion. We also discuss how the unique structure of Nafion affects the fluorescence behavior of acridine at various pH values and examine the impact of buffer concentration on apparent pKa and pH sensing ability. PMID:14610939

Ryder, Alan G; Power, Sarah; Glynn, Thomas J

2003-01-01

207

Designing reaction-based fluorescent probes for selective hydrogen sulfide detection.  

PubMed

Hydrogen sulfide (H2S) is a biologically generated, gaseous signaling molecule that mediates a wide range of physiological functions and is misregulated in numerous pathologies ranging from neurodegenerative disease to hypertension to diabetes. Despite swelling interest, a deeper understanding of the biological roles played by H2S has been hindered by a lack of tools for the real-time visualization of its production in living organisms. Recently, reaction-based fluorescent probes have emerged as an ideal approach for selective H2S imaging and are attracting increasing attention with many new innovative designs being introduced. This review will highlight some of the most fruitful reaction-based strategies, including reduction-based, nucleophilic-based, and metal sulfide precipitation-based fluorescent sensors. Strategies to address the key design challenges of sensitivity, selectivity, in vivo compatibility, and quantification will be discussed using examples of recently developed molecular scaffolds for selective H2S detection. PMID:24239492

Lippert, Alexander R

2014-04-01

208

Classical low-coherence interferometry based on broadband parametric fluorescence and amplification.  

PubMed

We demonstrate that single-mode broadband amplified spontaneous parametric downconversion, combined with optical parametric amplification, can be used as a classical source of phase-sensitive cross-correlated beams. We first study the single spatial mode emission and the spectral brightness properties of the parametric fluorescence, produced in periodically poled MgO-doped lithium niobate. Using the same single-pass bulk-crystal configuration for a pulsed optical parametric amplifier, we achieve a gain of approximately 20 dB at an average pump power of 2W, and explain the pulse narrowing observed at the output of both parametric fluorescence and amplification in the regime of high gain. Combining these two nonlinear processes, we measured optical coherence tomography signals with standard InGaAs photodiodes, thus realizing the first classical interferometer based on amplified parametric fluorescence. The results suggest their utility for demonstrating phase-conjugate optical coherence tomography. PMID:19907576

Le Gouët, Julien; Venkatraman, Dheera; Wong, Franco N C; Shapiro, Jeffrey H

2009-09-28

209

Substituent-dependent fluorescent sensors for zinc ions based on carboxamidoquinoline.  

PubMed

A series of carboxamidoquinoline-based fluorescent sensors (the AQZ family) were synthesized and characterized. The AQZ family members were highly soluble in water and showed good selectivity for Zn(2+)via enhanced fluorescence in aqueous buffer solution. Fluorescence signals could be tuned from dual-wavelength ratiometric changes to changes in the intensity of a single wavelength upon binding Zn(2+) through the introduction of different substituents onto the quinoline ring. Concentrations of free Zn(2+) of 10(-5)-10(-6) M could be detected using the sensors. Changes of substituents and their positions on the quinoline ring influenced the sensitivity for Zn(2+), but had little effect on Zn(2+) affinities. PMID:22903380

Zhang, Yu; Guo, Xiangfeng; Jia, Lihua; Xu, Shicheng; Xu, Zhihui; Zheng, Libo; Qian, Xuhong

2012-10-14

210

Assessment of fluorescein-based fluorescent dyes for tracing Neotyphodium endophytes in planta.  

PubMed

Fluorescent dyes were assessed for their ability to stain viable hyphae of the fungi Neotyphodium lolii and N. coenophialum, symbiotic endophytes of the Pooideae grasses Lolium perenne and Festuca arundinacea, respectively. The fluorescein-based fluorophores; fluorescein diacetate (FDA), 5(6)-carboxy-fluorescein diacetate (CFDA), 5-chloromethylfluorescein diacetate (CMFDA) and the chitin-binding stain, Calcofluor while M2R, were assessed for staining of endophyte hyphae in vitro from axenic fungal cultures and in planta, including epidermal leaf sheath peels, nodes, ovaries, embryos and meristems. CMFDA produced the greatest intensity of staining of fungal hyphae and gave excellent contrast in planta compared to the plant cells. Compared to the other dyes, CMFDA was also the least affected by photo bleaching and continued to fluoresce up to 2 h after initial excitation. None of the fluorescent dyes stained fungal hyphae in seed. PMID:22802389

Card, Stuart D; Tapper, Brian A; Lloyd-West, Catherine; Wright, Kathryn M

2013-01-01

211

Ratiometric fluorescence-based dissolved carbon dioxide sensor for use in environmental monitoring applications.  

PubMed

The focus of this work is on the development and characterisation of a fluorescence-based ratiometric sol-gel-derived dissolved carbon dioxide (dCO(2)) sensor for use in environmental monitoring applications. Fluorescence-based dCO(2) sensors are attractive as they facilitate the development of portable and low-cost systems that can be easily deployed outside the laboratory environment. The sensor developed for this work exploits a pH fluorescent dye 1-hydroxypyrene-3,6,8-trisulfonic acid, ion-paired with cetyltrimethylammonium bromide (HPTS-IP), which has been entrapped in a hybrid sol-gel-based matrix derived from n-propyltriethoxysilane along with the liphophilic organic base. The sensor spot deposited on a cover slip has been interrogated with a robust, ratiometric optical probe that combines effective fluorescence excitation and detection and thus facilitates the production of a highly sensitive sensor system using low-cost optoelectronic components. The probe design involves the use of dual-LED excitation in order to facilitate ratiometric operation and uses a silicon PIN photodiode. HPTS-IP exhibits two pH-dependent changes in excitation bands, which allows for dual excitation ratiometric detection as an indirect measure of the dCO(2). Such measurements are insensitive to changes in dye concentration, leaching and photobleaching of the fluorophore and instrument fluctuations unlike unreferenced fluorescence intensity measurements. The performance of the sensor system is characterised by a high degree of repeatability, reversibility and stability. Calculated limit of detection for the sensor was 35 ppb. The sensor probe was used to monitor dCO(2) levels in a laboratory-based aquatic habitat, and the expected diurnal pattern was clearly visible. The influence of temperature, biofouling and photobleaching on sensor performance has been also investigated. PMID:20827465

Wencel, Dorota; Moore, John P; Stevenson, Niall; McDonagh, Colette

2010-11-01

212

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

213

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

214

Rapid high-throughput assessment of aerobic bacteria in complex samples by fluorescence-based oxygen respirometry.  

PubMed

A simple method has been developed for the analysis of aerobic bacteria in complex samples such as broth and food homogenates. It employs commercial phosphorescent oxygen-sensitive probes to monitor oxygen consumption of samples containing bacteria using standard microtiter plates and fluorescence plate readers. As bacteria grow in aqueous medium, at certain points they begin to deplete dissolved oxygen, which is seen as an increase in probe fluorescence above baseline signal. The time required to reach threshold signal is used to either enumerate bacteria based on a predetermined calibration or to assess the effects of various effectors on the growth of test bacteria by comparison with an untreated control. This method allows for the sensitive (down to a single cell), rapid (0.5 to 12 h) enumeration of aerobic bacteria without the need to conduct lengthy (48 to 72 h) and tedious colony counts on agar plates. It also allows for screening a wide range of chemical and environmental samples for their toxicity. These assays have been validated with different bacteria, including Escherichia coli, Micrococcus luteus, and Pseudomonas fluorescens, with the enumeration of total viable counts in broth and industrial food samples (packaged ham, chicken, and mince meat), and comparison with established agar plating and optical-density-at-600-nm assays has been given. PMID:16461677

O'Mahony, Fiach C; Papkovsky, Dmitri B

2006-02-01

215

Metal Enhanced Fluorescence Solution-based Sensing Platform 2: Fluorescent Core-Shell Ag@SiO 2 Nanoballs  

Microsoft Academic Search

In this Rapid Communication, we present the development of monodisperse core-shell (silver core-silica shell) nanoparticles\\u000a with various shell thicknesses featuring a fluorophore, subsequently named Metal-Enhanced Fluorescence (MEF) nanoballs. MEF\\u000a nanoballs consist of a ?130 nm silver nanoparticle core, a silica shell with up to 35 nm thickness and fluorophores doped within the silica shell.\\u000a Fluorescent nanobubbles where the silver core is removed

Kadir Aslan; Meng Wu; Joseph R. Lakowicz; Chris D. Geddes

2007-01-01

216

A novel fluorescence-based assay for the transglycosylation activity of endo-?- N-acetylglucosaminidases  

Microsoft Academic Search

A fluorescence-based assay for the transglycosylation activity of endo-?-N-acetylglucosaminidases (ENGases) was developed. The assay was based on the findings that a coupled chitinase can specifically capture and hydrolyze the fluorogenic intermediate that is formed by the ENGase-catalyzed transglycosylation to release a fluorophore, but does not hydrolyze the donor asparagine-linked N-glycan and the acceptor 4-methylumbelliferyl N-acetylglucosaminide. The assay method was verified

Steven Hauser; Haijing Song; Hengguang Li; Lai-Xi Wang

2005-01-01

217

CMOS image sensor-based implantable glucose sensor using glucose-responsive fluorescent hydrogel  

PubMed Central

A CMOS image sensor-based implantable glucose sensor based on an optical-sensing scheme is proposed and experimentally verified. A glucose-responsive fluorescent hydrogel is used as the mediator in the measurement scheme. The wired implantable glucose sensor was realized by integrating a CMOS image sensor, hydrogel, UV light emitting diodes, and an optical filter on a flexible polyimide substrate. Feasibility of the glucose sensor was verified by both in vitro and in vivo experiments.

Tokuda, Takashi; Takahashi, Masayuki; Uejima, Kazuhiro; Masuda, Keita; Kawamura, Toshikazu; Ohta, Yasumi; Motoyama, Mayumi; Noda, Toshihiko; Sasagawa, Kiyotaka; Okitsu, Teru; Takeuchi, Shoji; Ohta, Jun

2014-01-01

218

Ultrathin oligonucleotide layers for fluorescence-based DNA sensors  

NASA Astrophysics Data System (ADS)

Preliminary investigations into the design of an affinity sensor using evanescent wave technology concentrate upon the means of immobilization of the receptor molecules. In this work DNA served as the selective recognition element. The molecular principle of a sequence-selective biosensor for DNA is based on a sandwich-hybridization assay wherein the analyte, a single-stranded (ss)DNA, bound specifically to both an immobilized capture probe and a dye-labeled oligonucleotide in free solution. The efficiency of the capture array depends on the density of highly organized oligonucleotides on the waveguide surface and correlates therefore directly with the specificity and the sensitivity of the sensor. In the present approach using the Langmuir- Blodgett technique cinnamoylbutylether-cellulose monolayers were transferred onto optical fibers or planar waveguides. These films served as matrices for the immobilization of biotinylated oligonucleotides via streptavidin. For the first time streptavidin was immobilized by that manner. The specificity of the streptavidin layer or the following bounded nucleic acid molecules were controlled by an enzyme- linked immunosorbent assay (ELISA). Finally, this application has also shown to be suitable for the detection of Salmonella, which is an important pathogen associated with acute gastroenteritidis and food borne diseases.

Furch, M.; Ueberfeld, J.; Hartmann, Andreas; Bock, Daniel; Seeger, Stefan

1996-11-01

219

Double-cladding-fiber-based detection system for intravascular mapping of fluorescent molecular probes  

NASA Astrophysics Data System (ADS)

Early detection of high-risk coronary atherosclerosis remains an unmet clinical challenge. We have previously demonstrated a near-infrared fluorescence catheter system for two-dimensional intravascular detection of fluorescence molecular probes [1]. In this work we improve the system performance by introducing a novel high resolution sensor. The main challenge of the intravascular sensor is to provide a highly focused spot at an application relevant distance on one hand and a highly efficient collection of emitted light on the other. We suggest employing a double cladding optical fiber (DCF) in combination with focusing optics to provide a sensor with both highly focused excitation light and highly efficient fluorescent light collection. The excitation laser is coupled into the single mode core of DCF and guided through a focusing element and a right angle prism. The resulting side-fired beam exhibits a small spot diameter (50 ?m) throughout a distance of up to 2 mm from the sensor. This is the distance of interest for intravascular coronary imaging application, determined by an average human coronary artery diameter. At the blood vessel wall, an activatable fluorescence molecular probe is excited in the diseased lesions. Next light of slightly shifted wavelength emits only in the places of the inflammations, associated with dangerous plaques [2]. The emitted light is collected by the cladding of the DCF, with a large collection angle (NA=0.4). The doublecladding acts as multimodal fiber and guides the collected light to the photo detection elements. The sensor automatically rotates and pulled-back, while each scanned point is mapped according to the amount of detected fluorescent emission. The resulting map of fluorescence activity helps to associate the atherosclerotic plaques with the inflammation process. The presented detection system is a valuable tool in the intravascular plaque detection and can help to differentiate the atherosclerotic plaques based on their biological activity, identify the ones that prone to rupture and therefore require more medical attention.

Razansky, R. Nika; Rozental, Amir; Mueller, Mathias S.; Deliolanis, Nikolaos; Jaffer, Farouc A.; Koch, Alexander W.; Ntziachristos, Vasilis

2011-03-01

220

Novel Fluorescence-Based Screen To Identify Small Synthetic Internal Ribosome Entry Site Elements  

PubMed Central

We report here a novel fluorescent protein-based screen to identify small, synthetic internal ribosome entry site (IRES) elements in vivo. A library of bicistronic plasmids encoding the enhanced blue and green fluorescent proteins (EBFP and EGFP) separated by randomized 50-nucleotide-long sequences was amplified in bacteria and delivered into mammalian cells via protoplast fusion. Cells that received functional IRES elements were isolated using the EBFP and EGFP reporters and fluorescence-activated cell sorting, and several small IRES elements were identified. Two of these elements were subsequently shown to possess IRES activity comparable to that of a variant of the encephalomyocarditis virus IRES element in a context-independent manner both in vitro and in vivo, and these elements functioned in multiple cell types. Although no sequence or structural homology was apparent between the synthetic IRES elements and known viral and cellular IRES elements, the two synthetic IRES elements specifically blocked poliovirus (PV) IRES-mediated translation in vitro. Competitive protein-binding experiments suggested that these IRES elements compete with PV IRES-mediated translation by utilizing some of the same factors as the PV IRES to direct translation. The utility of this fluorescent protein-based screen in identifying IRES elements with improved activity as well as in probing the mechanism of IRES-mediated translation is discussed. PMID:11283261

Venkatesan, Arun; Dasgupta, Asim

2001-01-01

221

A fluorescence aptasensor based on DNA charge transport for sensitive protein detection in serum.  

PubMed

A novel fluorescence aptasensor based on DNA charge transport for sensitive protein detection has been developed. A 15nt DNA aptamer against thrombin was used as a model system. The aptamer was integrated into a double strand DNA (dsDNA) that was labeled with a hole injector, naphthalimide (NI), and a fluorophore, Alexa532, at its two ends. After irradiation by UV light, the fluorescence of Alexa532 was bleached due to the oxidization of Alexa532 by the positive charge transported from naphthalimide through the dsDNA. In the presence of thrombin, the binding of thrombin to the aptamer resulted in the unwinding of the dsDNA into ssDNA, which led to the blocking of charge transfer and the strong fluorescence emission of Alexa532. By monitoring the fluorescence signal change, we were able to detect thrombin in homogeneous solutions with high selectivity and high sensitivity down to 1.2 pM. Moreover, as DNA charge transfer is resistant to interferences from biological contexts, the aptasensor can be used directly in undiluted serum with similar sensitivity as that in buffer. This new sensing strategy is expected to promote the exploitation of aptamer-based biosensors for protein assays in complex biological matrixes. PMID:21949940

Zhang, Xinyue; Zhao, Zilong; Mei, Hongcheng; Qiao, Yupu; Liu, Qiaoling; Luo, Wangxi; Xia, Tie; Fang, Xiaohong

2011-11-21

222

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

223

Simple high-performance liquid chromatography-fluorescence detection method for plasma, kidney and liver of rat as a tool for toxicology studies.  

PubMed

A fast and simple HPLC-FLD (high-performance liquid chromatography-fluorescence detection) analytical method has been developed and validated for the determination of ochratoxin A in rat plasma, kidney and liver. The extraction method, calibration curves and chromatographic conditions are common for the three matrices. Plasma and homogenized tissue samples (250 microL) were extracted with ethanol (400 microL) and trichloroacetic acid 20% (w/v) (50 microL). Supernatants were directly injected into the HPLC system, analyzed on a 5-microm (25 cm x 0.4 cm) Tracer Extrasil ODS2 column using FLD (excitation wavelength=225 nm, emission wavelength=461 nm). The mobile phase was 29:29:42 (v/v) methanol-acetonitrile-sodium acetate. The small volume of sample needed which allows the obtaining of ochratoxin A levels in individual tissue samples from small animals and the wide range of concentrations that could be analyzed make this method easy to apply in toxicology and toxicokinetic studies of this mycotoxin, even in low dose carcinogenic studies. This method was linear and selective for all the matrices. Precision and accuracy were always <10% and recovery was very efficient in each case. Limits of detection and quantification were also calculated in plasma (1 and 8.4 microg/L), kidney (14.3 and 55.8 microg/kg) and liver (4.1 and 52.8 microg/kg). Stability of the tissue homogenates was assured for at least 10 months at -80 degrees C. The method has been successfully applied to the analysis of rat samples after 7 days of ochratoxin A (0.5mg/kg b.w. dissolved in an aqueous NaHCO(3) solution) administration by oral gavage. PMID:19027908

Vettorazzi, Ariane; Gonzalez-Peñas, Elena; Arbillaga, Leire; Corcuera, Laura-Ana; López de Cerain, Adela

2008-12-26

224

Simple networks and learning rules for spike-timing based computation: learning rules  

E-print Network

Simple networks and learning rules for spike-timing based computation: learning rules J. J are the essential dynamical computational features. This network implemented a 'many are equal' computing primitive, we constructed a network capable of solving some of the computational problems that arise

Moehlis, Jeff

225

Molecular dynamics study of the structure and performance of simple and double bases propellants  

Microsoft Academic Search

To investigate the structure and performance of simple and double bases propellants, the nitrocellulose (NC), nitroglycerin (NG), and double mixed system (NC+NG) have been simulated by using the molecular dynamics (MD) method with the COMPASS force field. The interactions between NC and NG have been analyzed by means of pair correlation functions. The mechanical properties of the three model systems,

Xiufang Ma; Weihua Zhu; Jijun Xiao; Heming Xiao

2008-01-01

226

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

227

A simple method for estimating evolutionary rates of base substitutions through comparative studies of nucleotide sequences  

Microsoft Academic Search

Summary Some simple formulae were obtained which enable us to estimate evolutionary distances in terms of the number of nucleotide substitutions (and, also, the evolutionary rates when the divergence times are known). In comparing a pair of nucleotide sequences, we distinguish two types of differences; if homologous sites are occupied by different nucleotide bases but both are purines or both

Motoo Kimura

1980-01-01

228

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.

229

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

E-print Network

made from inexpensive papers like paper towels ($0.2/m2 ).2 The features made using wax printingUnderstanding Wax Printing: A Simple Micropatterning Process for Paper-Based Microfluidics Emanuel in paper using a commercially avail- able printer and hot plate. The printer prints patterns of solid wax

Prentiss, Mara

230

Flagellar Length Control System: Testing a Simple Model Based on Intraflagellar Transport and Turnover  

Microsoft Academic Search

Flagellar length regulation provides a simple model system for addressing the general problem of organelle size control. Based on a systems-level analysis of flagellar dynamics, we have proposed a mechanism for flagellar length control in which length is set by the balance of continuous flagellar assembly and disassembly. The model proposes that the assembly rate is length dependent due to

Wallace F. Marshall; Hongmin Qin; Monica Rodrigo Brenni; Joel L. Rosenbaum

2005-01-01

231

This simple method is based on the measurement of the size of subcutaneous  

E-print Network

This simple method is based on the measurement of the size of subcutaneous adipose cells removed the literature, revealed that adipose cell size surpassed by 20% the expected genetic progress of an equivalent% decrease in lipid deposition between birth and 95 d of age, and a reduction of adipose cell hypertrophy

Boyer, Edmond

232

Page 1 of 2 Simple Medium based on BOD test solutions  

E-print Network

Page 1 of 2 Simple Medium based on BOD test solutions B.E. Logan, Penn State University If you demand (BOD) test used at wastewater treatment plants around the world. To make things even simpler, you can buy pre-made ingredients sold by different companies. For this example medium, we will used BOD

233

Conditionally fluorescent molecular probes for detecting single base changes in double-stranded DNA  

PubMed Central

Small variations in nucleic acid sequences can have far-reaching phenotypic consequences. Reliably distinguishing closely related sequences is therefore important for research and clinical applications. Here, we demonstrate that conditionally fluorescent DNA probes are capable of distinguishing variations of a single base in a stretch of target DNA. These probes use a novel programmable mechanism in which each single nucleotide polymorphism generates two thermodynamically destabilizing mismatch bubbles rather than the single mismatch formed during typical hybridization-based assays. Up to 12,000-fold excess of a target containing a single nucleotide polymorphism is required to generate the same fluorescence as one equivalent of the intended target, and detection works reliably over a wide range of conditions. Using these probes we detected point mutations in a 198 base pair subsequence of the E. Coli rpoB gene. Our probes are constructed from multiple oligonucleotide fragments, circumventing synthesis limitations and enabling long continuous DNA sequences to be probed. PMID:23965681

Chen, Sherry Xi; Zhang, David Yu; Seelig, Georg

2013-01-01

234

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

235

Patterning pallet arrays for cell selection based on high-resolution measurements of fluorescent biosensors  

PubMed Central

Pallet arrays enable cells to be separated while they remain adherent to a surface and provide a much greater range of cell selection criteria relative to that of current technologies. However there remains a need to further broaden cell selection criteria to include dynamic intracellular signaling events. To demonstrate the feasibility of measuring cellular protein behavior on the arrays using high resolution microscopy, the surfaces of individual pallets were modified to minimize the impact of scattered light at the pallet edges. The surfaces of the three-dimensional pallets on an array were patterned with a coating such as fibronectin using a customized stamping tool. Micropatterns of varying shape and size were printed in designated regions on the pallets in single or multiple steps to demonstrate the reliability and precision of patterning molecules on the pallet surface. Use of a fibronectin matrix stamped at the center of each pallet permitted the localization of H1299 and mouse embryonic fibroblast (MEF) cells to the pallet centers and away from the edges. Compared to pallet arrays with fibronection coating the entire top surface, arrays with a central fibronectin pattern increased the percentage of cells localized to the pallet center by 3-4 fold. Localization of cells to the pallet center also enabled the physical separation of cells from optical artifacts created by the rough pallet side walls. To demonstrate the measurement of dynamic intracellular signaling on the arrays, fluorescence measurements of high spatial resolution were performed using a RhoA GTPase biosensor. This biosensor utilized fluorescence resonance energy transfer (FRET) between cyan fluorescent protein (CFP) and yellow fluorescent protein (YFP) to measure localized RhoA activity in cellular ruffles at the cell periphery. These results demonstrated the ability to perform spatially resolved measurements of fluorescence-based sensors on the pallet arrays. Thus, the patterned pallet arrays should enable novel cell separations in which cell selection is based on complex cellular signaling properties. PMID:21621038

Shadpour, Hamed; Zawistowski, Jon S.; Herman, Annadele; Hahn, Klaus; Allbritton, Nancy L.

2011-01-01

236

Chemodosimeter-based fluorescent detection of L-cysteine after extracted by molecularly imprinted polymers.  

PubMed

A chemodosimeter-based fluorescent detection method coupled with molecularly imprinted polymers (MIPs) extraction was developed for determination of L-cysteine (L-Cys) by combining molecular imprinting technique with fluorescent chemodosimeter. The MIPs prepared by precipitation polymerization with L-Cys as template, possessed high specific surface area of 145 m(2)/g and good thermal stability without decomposition lower than 300 °C, and were successfully applied as an adsorbent with excellent selectivity for L-Cys over other amino acids, and enantioselectivity was also demonstrated. A novel chemodosimeter, rhodamine B1, was synthesized for discriminating L-Cys from its structurally similar homocysteine and glutathione as well as various possibly co-existing biospecies in aqueous solutions with notable fluorescence enhancement when adding L-Cys. As L-Cys was added with increasing concentrations, an emission band peaked at 580 nm occurred and significantly increased in fluorescence intensity, by which the L-Cys could be sensed optically. High detectability up to 12.5 nM was obtained. An excellent linearity was found within the wide range of 0.05-50 ?M (r=0.9996), and reasonable relative standard deviations ranging from 0.3% to 3.5% were attained. Such typical features as high selectivity, high sensitivity, easy operation and low cost enabled this MIPs-fluorometry to be potentially applicable for routine detection of trace L-Cys. PMID:24468373

Cai, Xiaoqiang; Li, Jinhua; Zhang, Zhong; Wang, Gang; Song, Xingliang; You, Jinmao; Chen, Lingxin

2014-03-01

237

TiO2-nanotube-based dye-sensitized solar cells containing fluorescent material.  

PubMed

We fabricated a dye-sensitized solar cells (DSCs) with TiO2 nanotube arrays obtained by anodization of Ti foil. Vertical structure of TiO2 nanotube arrays is very attractive due to a high electron transfer from dye to electrode. To improve the power conversion efficiency, fluorescent material, F-6377, was applied in TiO2-nanotube-based DSCs to use a light spectrum efficiently. Fluorescent material was absorbed the different wavelength of 460 nm from the light absorbed by N719 dye. Fluorescent material to emit the absorbed light energy provided an additional light for dye in DSCs and additional electrons was generated. Thickness of TiO2 nanotube arrays grown by anodic oxidation was 15 microm. N719 dye and 13(-)/l(-) electrolyte were used to fabricate the DSCs. The short circuit current densities (J(sc)) and the power conversion efficiency in DSCs with fluorescent were 10.8 mA/cm2 and 2.48%, respectively. Electrochemical impedance spectroscopy (EIS) was observed to understand an electron transfer and life time. PMID:23858885

Kim, Woong-Rae; Lee, Young-Joon; Park, Hun; Lee, Jae-Joon; Choi, Won-Youl

2013-05-01

238

Matrix Effects on the Microcystin-LR Fluorescent Immunoassay Based on Optical Biosensor  

PubMed Central

Matrix effects on the microcystin-LR fluorescent immunoassay based on the evanescent wave all-fiber immunosensor (EWAI) and their elimination methods were studied. The results indicated that PBS and humic acid did not affect the monitoring of samples under the investigated conditions. When the pH was less than 6 or higher than 8, the fluorescence signals detected by immunosensor systems were obviously reduced with the decrease or increase of pH. When the pH ranged from 6 to 8, IC50 and the linear working range of MC-LR calculated from the detection curves were 1.01?1.04 ?g/L and 0.12?10.5 ?g/L, respectively, which was favourable for an MC-LR immunoassay. Low concentrations of Cu2+ rarely affected the detection performance of MC-LR. When the concentration of CuSO4 was higher than 5 mg/L, the fluorescence signal detected by EWAI clearly decreased, and when the concentration of CuSO4 was 10 mg/L, the fluorescence signal detected was reduced by 70%. The influence of Cu2+ on the immunoassay could effectively be compromised when chelating reagent EDTA was added to the pre-reaction mixture. PMID:22574059

Long, Feng; Zhu, An-na; Sheng, Jian-Wu; He, Miao; Shi, Han-Chang

2009-01-01

239

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

240

Cyclin B1 Destruction Box-Mediated Protein Instability: The Enhanced Sensitivity of Fluorescent-Protein-Based Reporter Gene System  

PubMed Central

The periodic expression and destruction of several cyclins are the most important steps for the exact regulation of cell cycle. Cyclins are degraded by the ubiquitin-proteasome system during cell cycle. Besides, a short sequence near the N-terminal of cyclin B called the destruction box (D-box; CDB) is also required. Fluorescent-protein-based reporter gene system is insensitive to analysis because of the overly stable fluorescent proteins. Therefore, in this study, we use human CDB fused with both enhanced green fluorescent protein (EGFP) at C-terminus and red fluorescent protein (RFP, DsRed) at N-terminus in the transfected human melanoma cells to examine the effects of CDB on different fluorescent proteins. Our results indicated that CDB-fused fluorescent protein can be used to examine the slight gene regulations in the reporter gene system and have the potential to be the system for screening of functional compounds in the future. PMID:24416725

Yang, Chao-Hsun; Kuo, Wan-Ting; Chuang, Yun-Ting; Chen, Cheng-Yu

2013-01-01

241

Detection of saccharides with a fluorescent sensing device based on a gold film modified with 4-mercaptophenylboronic acid monolayer  

NASA Astrophysics Data System (ADS)

An extremely sensitive fluorescent sensor based on a phenylboronic acid monolayer was developed for detecting saccharide molecules. The fluorescent sensor was prepared by assembling a monolayer of 4-mercaptophenylboronic acid (4-MPBA) onto a gold-coated compact disk. The change in the fluorescence of the 4-MPBA monolayer was extremely obvious in basic methanolic buffer containing monosaccharides down to the picomolar level. The fluorescence spectra demonstrated that the 4-MPBA monolayer was sensitive to monosaccharides and disaccharides, and the affinity of the monolayer toward saccharides was in the order of glucose < fructose < mannose < galactose < maltose > lactose > sucrose. Additionally, the fluorescence intensity of 4-MPBA monolayer was restorable after cleaning with weak acid, indicating that the reported fluorescent sensor with the detection limit of glucose down to the picomolar level is reusable for sensing saccharides.

Chen, Shu-Jen; Chang, Jui-Feng; Cheng, Nai-Jen; Yih, Jeng-Nan; Chiu, Kuo-Chi

2013-09-01

242

A fluorescence turn-on probe for cysteine and homocysteine based on thiol-triggered benzothiazolidine ring formation.  

PubMed

We synthesized a new coumarin-based probe TP, containing a disulfide moiety, to detect biothiols in cells. A fluorescence turn-on response is induced by the thiol-disulfide exchange of the probe, with subsequent intramolecular benzothiazolidine ring formation giving rise to a fluorescent product. The probe exhibits an excellent selectivity for cysteine (Cys) and homocysteine (Hcy) over glutathione (GSH) and other amino acids. The fluorescent probe also exhibits a highly sensitive fluorescence turn-on response to Cys and Hcy with detection limits of 0.8?M for Cys and 0.5?M for Hcy. In addition, confocal fluorescence microscopy imaging using RAW264.7 macrophages demonstrates that the probe TP could be an efficient fluorescent detector for thiols in living cells. PMID:25300219

Liu, Shi-Rong; Chang, Chao-Yiu; Wu, Shu-Pao

2014-11-01

243

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

244

A fluorescent nanoprobe based on graphene oxide fluorescence resonance energy transfer for the rapid determination of oncoprotein vascular endothelial growth factor (VEGF).  

PubMed

Oncoprotein vascular endothelial growth factor (VEGF) is one of the most critical growth factors that regulates tumor growth and division. The vascular endothelial growth factor (VEGF) is also an important biomarker for different diseases and clinical disorders. Herein, we propose a graphene oxide (GO) fluorescence resonance energy transfer (FRET)-based aptasensor for rapid, sensitive, and selective detection of VEGF in homogeneous solution. The fluorescent dye-labeled anti-VEGF aptamer is adsorbed on the surface of GO via ?-? interaction between the flat planar GO sheets and the ring structures in the nucleobases, which results in the fluorescence quenching of the dye due to the highly effective FRET from the dye to GO. Upon recognition and binding with the target VEGF, it specifically forms a VEGF/aptamer complex and then release from the GO surface, leading to the restoration of fluorescence signal of the dye. This GO-based sensing platform exhibits high sensitivity and specificity toward VEGF versus other proteins, with the detection limits corresponding to 2.5×10(-10) M. The sensitivity of this new type of aptamer-based assay is at least one order of magnitude higher than that of conventional homogeneous optical assays. Moreover, the application of this nanosensor for human serum sample analysis is also demonstrated. The GO/aptamer-based assay approach holds great promise as a general platform for detection of a variety of target molecules. PMID:24160878

Wang, Sheng-E; Si, Shihui

2013-11-01

245

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

246

Doping cobalt into a [Zn?] cluster-based MOF to tune magnetic behaviour and induce fluorescence signal mutation.  

PubMed

An in situ doping strategy was successfully applied to tune the magnetic behaviour and induce fluorescence signal mutation of a spindle heptanuclear zinc cluster-based MOF, by only modifying its structural composition. The Co(II)-doped Zn(II)-MTV-M'MOF exhibits canted antiferromagnetism and weaker fluorescence properties. PMID:24957490

Li, Yun-Wu; Liu, Sui-Jun; Hu, Tong-Liang; Bu, Xian-He

2014-08-14

247

Assessment and Continued Validation of the Malaria SYBR Green I-Based Fluorescence Assay for Use in Malaria Drug Screening  

Microsoft Academic Search

Several new fluorescence malaria in vitro drug susceptibility microtiter plate assays that detect the presence of malarial DNA in infected erythrocytes have recently been reported, in contrast to traditional isotopic screens that involve radioactive substrate incorporation to measure in vitro malaria growth inhibition. We have assessed and further characterized the malaria SYBR Green I-based fluorescence (MSF) assay for its ability

Jacob D. Johnson; Richard A. Dennull; Lucia Gerena; Miriam Lopez-Sanchez; Norma E. Roncal; Norman C. Waters

2007-01-01

248

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

249

Synchronous fluorescence measurement of enrofloxacin in the pharmaceutical formulation and its residue in milks based on the yttrium (III)-perturbed luminescence.  

PubMed

A simple, rapid and sensitive synchronous fluorescence method is put forward for the determination of enrofloxacin (ENRO) in the pharmaceutical formulation and its residue in milk based on the yttrium (III)-perturbed luminescence. When Y(3+) is added into the ENRO solution, the fluorescence of ENRO is significantly enhanced. The synchronous fluorescence technology is employed in the method to determine trace amount of ENRO residue in milks. The synchronous fluorescence intensity of the system is measured in a 1-cm quartz cell with excitation wavelength of 328 nm, ??=80 nm. A good linear relationship between the fluorescence intensity and the ENRO concentration is obtained in the range of 1.0 × 10(-9) to 2.0 × 10(-6)mol L(-1) (r(2)=0.9992). The limit of detection (LOD) of this method attains as low as 3.0 × 10(-10) mol L(-1) (S/N=3). The selectivity of this method is also very good. Common metal ions, rare-earth ions and some pharmaceuticals, which are usually used together with ENRO, do not interfere with the determination of ENRO under the actual conditions. The proposed method can be applied to determine ENRO residue in milks, and limit of quantification (LOQ) determined in the spiked milk is estimated to be 2.8 × 10(-8) mol L(-1) (10 ?g L(-1)). Moreover, this method can be used as a rapid screening for judging whether the ENRO residues in milks exceed Minimal Risk Levels (MRLs) or not. In addition, the mechanism of the fluorescence enhancement is also discussed in detail. PMID:20875588

Tong, Changlun; Zhuo, Xiajun; Liu, Weiping; Wu, Jianmin

2010-10-15

250

Phenotyping transgenic embryos: a rapid 3-D screening method based on episcopic fluorescence image capturing  

Microsoft Academic Search

We describe a technique suitable for routine three-dimensional (3-D) analysis of mouse embryos that is based on episcopic fluorescence images captured during serial sectioning of wax-embedded specimens. We have used this procedure to describe the cardiac phenotype and associated blood vessels of trisomic 16 (Ts16) and Cited2-null mutant mice, as well as the expression pattern of an Myf5 enhancer\\/?-galactosidase transgene.

Wolfgang Johann Weninger; Timothy Mohun

2001-01-01

251

Novel Fluorescence-Based Screen To Identify Small Synthetic Internal Ribosome Entry Site Elements  

Microsoft Academic Search

We report here a novel fluorescent protein-based screen to identify small, synthetic internal ribosome entry site (IRES) elements in vivo. A library of bicistronic plasmids encoding the enhanced blue and green fluores- cent proteins (EBFP and EGFP) separated by randomized 50-nucleotide-long sequences was amplified in bacteria and delivered into mammalian cells via protoplast fusion. Cells that received functional IRES elements

ARUN VENKATESAN; ASIM DASGUPTA

2001-01-01

252

Low molecular weight Neutral Boron Dipyrromethene (Bodipy) dyads for fluorescence-based neural imaging  

NASA Astrophysics Data System (ADS)

The neutral low molecular weight julolidine-based borondipyrromethene (Bodipy) dyads JULBD and MJULBD were used for fast voltage-sensitive dye imaging of neurons in the crab stomatogastric ganglion. The fluorescence modulation of the dyads mirrors alterations in the membrane potential of the imaged neurons. The toxicity of the dyes towards the neurons is related to their structure in that methyl groups at the 3,5 positions results in reduced toxic effects.

Bai, Dan; Benniston, Andrew C.; Clift, Sophie; Baisch, Ulrich; Steyn, Jannetta; Everitt, Nicola; Andras, Peter

2014-05-01

253

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

254

Fabrication of Dye-sensitized Solar Cells and Fluorescence Quenching Study Using Thiophene Based Copolymers  

Microsoft Academic Search

Photovoltaic performance of dye sensitized solar cells fabricated with a commercially available thiophene based copolymer was investigated. Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(bithiophene)], a highly soluble polythiophene, was used as a sensitizer. An open-circuit voltage of 0.64 V and a short-circuit current density of 0.36 mA\\/cm were measured. The incident photon to current conversion efficiency for the polymer was measured. Fluorescence from the other polythiophene,

Soumitra Satapathi; Fadong Yan; Robinson Anandakathir; Ke Yang; Lian Li; Ravi Mosurkal; Lynne A. Samuelson; Jayant Kumar

2010-01-01

255

Development of rapid microbial methods for lysine quantification in feed ingredients based on green fluorescent protein fluorescence  

E-print Network

to extracellular lysine measured as OD, it can be relatively time consuming (10-12h). Therefore, more rapid assays are needed if pre-formulation estimates are required. In this dissertation whole cell fluorescent biosensors for the quantification of bioavailable...

Chalova-Zhekova, Vesela I.

2007-04-25

256

Nanoscale contact line visualization based on Total Internal Reflection Fluorescence Microscopy.  

PubMed

We describe a novel measurement method to study the contact line of a droplet at nanoscale level. The method is based on Total Internal Reflection Fluorescence Microscopy (TIRFM), which uses an evanescent excitation field produced by total internal reflection of light. The evanescent field depends on the angle of the incident light and has an exponential intensity decay, characterized by the penetration depth. The penetration depth is determined by imaging a fluorescent particle probe that is traversed using an Atomic Force Microscopy (AFM) setup. The result confirms the exponential behavior of the evanescent field intensity, and the value of the penetration depth also corresponds with the value predicted based on the optical configuration. By using the intensity distribution of a fluorescent dye and the value for the penetration depth of the evanescent wave, it is possible to reconstruct the interface of a partial wetting droplet. The reconstructed interface based on TIRFM is in good agreement with the interface obtained from two reference measurements: non-disturbing AFM-imaging and conventional contact angle measurement. The latter lacks spatial resolution, while the former is limited to particular droplets. This new non-contact measurement does not suffer from these drawbacks, making it a very useful tool to study the fundamental wetting behavior of both stationary and dynamic interfaces. PMID:24216833

Franken, M J Z; Poelma, C; Westerweel, J

2013-11-01

257

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

258

High-speed DNA sequencing: An approach based upon fluorescence detection of single molecules  

SciTech Connect

This document discusses the development of a laser based technique for the rapid sequencing of large fragments of DNA based upon the detection of single, fluorescently tagged nucleotides cleaved from a single DNA fragments. Demonstrated is significant progress on several of the important steps of this technique. The projected rate of sequencing is several hundred bases per second which is orders of magnitude faster than existing methods. Once developed, this technology could be utilized by investigators for rapid sequencing of genetic material from virtually any source. 24 refs., 4 figs.

Jett, J.H.; Keller, R.A.; Martin, J.C.; Marrone, B.L.; Moyzis, R.K.; Ratliff, R.L.; Seitzinger, N.K.; Shera, E.B.; Stewart, C.C.

1989-01-01

259

RNA-ID, a highly sensitive and robust method to identify cis-regulatory sequences using superfolder GFP and a fluorescence-based assay.  

PubMed

We have developed a robust and sensitive method, called RNA-ID, to screen for cis-regulatory sequences in RNA using fluorescence-activated cell sorting (FACS) of yeast cells bearing a reporter in which expression of both superfolder green fluorescent protein (GFP) and yeast codon-optimized mCherry red fluorescent protein (RFP) is driven by the bidirectional GAL1,10 promoter. This method recapitulates previously reported progressive inhibition of translation mediated by increasing numbers of CGA codon pairs, and restoration of expression by introduction of a tRNA with an anticodon that base pairs exactly with the CGA codon. This method also reproduces effects of paromomycin and context on stop codon read-through. Five key features of this method contribute to its effectiveness as a selection for regulatory sequences: The system exhibits greater than a 250-fold dynamic range, a quantitative and dose-dependent response to known inhibitory sequences, exquisite resolution that allows nearly complete physical separation of distinct populations, and a reproducible signal between different cells transformed with the identical reporter, all of which are coupled with simple methods involving ligation-independent cloning, to create large libraries. Moreover, we provide evidence that there are sequences within a 9-nt library that cause reduced GFP fluorescence, suggesting that there are novel cis-regulatory sequences to be found even in this short sequence space. This method is widely applicable to the study of both RNA-mediated and codon-mediated effects on expression. PMID:23097427

Dean, Kimberly M; Grayhack, Elizabeth J

2012-12-01

260

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

261

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

262

An Experimental Research on Vector Control of Induction Motor Based on Simple Model  

Microsoft Academic Search

\\u000a Given the heavy computation, easy saturation and cumulate errors of conventional direct vector control, the vector control\\u000a of induction motor based on simple model is studied and the detailed scheme is described on the basis of the decomposing and\\u000a approximating the rotor flux. Because of the direct closed-loop control of the magnetizing current and the torque current\\u000a and the complex

Yinhai Zhang; Jinfa Ge; Weixia Liu; Qin Wang

2009-01-01

263

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

264

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

265

Polymer-coated fluorescent CdSe-based quantum dots for application in immunoassay.  

PubMed

The paper describes all stages of synthesis and characterization of biocompatible CdSe-based core/shell quantum dots (QDs) and their application as fluorescent label for immunoassay. Special attention was focused on development of maleic anhydride-based amphiphilic polymers for QDs solubilization in aqueous media. In this work two PEG-amines were tried for polymer modification: monoamine Jeffamine M 1000 used previously in some researches and diamine Jeffamine ED-2003 applied for the first time for QDs solubilization. The use of different Jeffamines allows us to obtain QDs with carboxyl or amine functional groups available for conjugation. The influence of polymer composition on optical properties of the nanocrystals and their stability in aqueous solutions as well as on their conjugation with biomolecules was studied. QDs with different coatings were used as biolabels in quantitative fluorescence microtiter plate immunoassay and qualitative on-site column test. It was found that quantum dots covered with amphiphilic polymer prepared from poly(maleic anhydride-alt-1-octadecene) and Jeffamine ED-2003 retained up to 90% of their initial brightness, easily conjugated with protein and showed low non-specific adsorption. In optimized conditions the obtained QDs were successfully used for determination of mycotoxin deoxynivalenol in wheat and maize samples by fluorescence microtiter plate immunoassay with an IC50 of 220 ?g kg(-1) and by on-site column test with cut-off of 500 ?g kg(-1). PMID:24140873

Speranskaya, Elena S; Beloglazova, Natalia V; Lenain, Pieterjan; De Saeger, Sarah; Wang, Zhanhui; Zhang, Suxia; Hens, Zeger; Knopp, Dietmar; Niessner, Reinhard; Potapkin, Dmitry V; Goryacheva, Irina Yu

2014-03-15

266

Technical considerations on confocal based fluorescence micro-optical sectioning tomography for visualizing brain circuits  

NASA Astrophysics Data System (ADS)

Imaging brain circuits is the basis for us to understand brain function and dysfunction. However, imaging axon at micrometer resolution while tracing the centimeter-scale axon projection across the whole-brain is still challenging. Here, we developed a fluorescence micro-optical sectioning tomography (fMOST) imaging system based on confocal fluorescence imaging scheme that can obtain whole brain image stack for visualizing brain circuits at neurite level. We use confocal detection to remove fluorescence background to clearly see one single neurite and use acoustical optical deflector (AOD), an inertia-free beam scanner to realize fast and prolonged stable imaging. We had acquired several complete datasets of whole-mouse brain at a one-micron voxel resolution. Based on these datasets, the uninterrupted tracing of brain-wide, long-distance axonal projections was demonstrated for the first time using a systematic reconstruction and annotation pipeline. Our method is believed to open an avenue to exploring both local and long-distance neural circuits that are related to brain functions and brain diseases down to the neurite level.

Qi, Xiaoli; Lv, Xiaohua; Xiong, Hanqing; Yan, Cheng; Chen, Jianling; Gong, Hui; Luo, Qingming; Zeng, Shaoqun

2014-03-01

267

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

268

A Zeeman-effect based scatter correction system for non-dispersive atomic fluorescence spectrometry  

NASA Astrophysics Data System (ADS)

A Zeeman-effect based method of correcting for the scattering of source radiation in atomic fluorescence spectrometry (AFS) is described. The magnetic field is applied to the atomization cell in a direction transverse to the source and detected beams. Both polarized and field modulated Zeeman AFS are examined. Fluorescence signals corrected for scattering are derived from differences in the measured light intensities caused by changes in the incident light polarization and/or field intensity. Results are given for the determination of Cd in an Al matrix, and for Cd, Hg, and Zn in NBS fly ash, orchard leaves, and river sediment. The scatter corrected values obtained by this method are in agreement with certified values.

Naranjit, D. A.; Radziuk, B. H.; Van Loon, J. C.

269

Development of a borondipyrromethene-based Zn2+ fluorescent probe: solvent effects on modulation sensing ability.  

PubMed

A borondipyrromethene-based Zn(2+) fluorescent probe BODPAQ was designed and synthesized. The chelators in BODPAQ, 2,2'-dipicolylamine (DPA) and 8-aminoquinoline (AQ), coordinate to Zn(2+) in a synergic manner. As a result, BODPAQ displays high Zn(2+) selectivity with a dramatic enhanced emission accompanied by a notable hypsochromic shift due to the binary inhibition effect of PET and ICT mechanisms, enabling the detection of Zn(2+) by both ratiometric and normal turn-on fluorescence methods in acetonitrile. Interestingly, the sensitivity of BODPAQ towards Zn(2+) changes upon varying the compositions of buffer solutions. In 3-morpholinopropanesulfonic acid (MOPS) buffer aqueous solution (50% CH(3)CN), BODPAQ displays the highest sensitivity for Zn(2+), while in citrate-phosphate buffer, BODPAQ shows no response to Zn(2+). PMID:22094853

Zhao, Chunchang; Zhang, Yulin; Feng, Peng; Cao, Jian

2012-01-21

270

New fluorescent bis-dithienylethene (DTE)-based bipyridines as reverse interrupters: single vs. double photochromism.  

PubMed

The synthesis and characterization of a series of fluorescent bis-dithienylethene (DTE)-based bipyridines, where the donor (D) and acceptor (A) groups are located on the same thiophene ring of the DTE unit, and their zinc(II) and rhenium(I) complexes are reported. Their photochromic properties have been investigated by UV-visible and (1)H NMR spectroscopy. These studies reveal that in non-polar solvents it is possible to modulate the photoreactivity, single vs. double ring-closure, by changing the nature of the donor group. The solvent effect, as well as the influence of the organometallic moieties on the photochromic behavior of these molecules, is also discussed. Finally, upon photoconversion to the photostationary state (PSS), a quenching of fluorescence is observed for the bipyridine ligands, due to disruption of the conjugation upon ring-closing. PMID:24365953

Ordronneau, Lucie; Boixel, Julien; Aubert, Vincent; Vidal, Matias S; Moya, Sergio; Aguirre, Pedro; Toupet, Loic; Williams, J A Gareth; Le Bozec, Hubert; Guerchais, Véronique

2014-02-14

271

One new dicoumarol-based fluorescent compound: Synthesis, crystal structure and metal ions recognition  

NASA Astrophysics Data System (ADS)

A new dicoumarol-based compound (C6H4)[CH2NHCO(C9O2H4)N(C2H5)2]21 was synthesized and characterized by IR, UV spectroscopy and single-crystal X-ray diffraction analysis. The structure of 1 exhibits a transoid formation with the two coumarin-containing arms sited on the two sides of the center benzene ring. In the crystal packing the molecule further interact with each other and form a three-dimensional framework through ?-? stacking interactions and multiform hydrogen bonds. The compound 1 shows the main emission peak at 540 nm corresponding to the green hue in the solid state. The fluorescence recognition behaviors for various metal ions were investigated and 1 exhibits a highly fluorescence-quenching selectivity for FeIII ion in the mixed CH3CNsbnd H2O solvent.

Bai, Yan; Yu, Ke; Pan, Hui; Dang, Dong-Bin

2013-09-01

272

Analog Integrated Circuit for Motion Detection with Simple-Shape Recognition Based on Frog Vision System  

NASA Astrophysics Data System (ADS)

We proposed in this research a novel two-dimensional network based on the frog visual system, with a motion detection function and a newly developed simple-shape recognition function, for use in object discrimination by integrated circuits. Specifically, the network mimics the signal processing of the small-field cell in a frog brain, consisting of the tectum and thalamus, which generates signals of the motion and simple shape of an object. The proposed network is constructed from simple analog complementary metal oxide semiconductor (CMOS) circuits; a test chip of the proposed network was fabricated with a 1.2 ?m CMOS process. Measurements on the chip clarified that the proposed network can generate signals of the moving direction, velocity, and simple shape, as well as perform information processing of the small-field cell. Results with the simulation program with integrated circuit emphasis (SPICE) showed that the analog circuits used in the network have low power consumption. Applications of the proposed network are expected to realize advanced vision chips with functions such as object discrimination and target tracking.

Nishio, Kimihiro; Yonezu, Hiroo; Furukawa, Yuzo

2007-09-01

273

Structure-guided Engineering Enhances a Phytochrome-based Infrared Fluorescent Protein*  

PubMed Central

Phytochrome is a multidomain dimeric red light photoreceptor that utilizes a chromophore-binding domain (CBD), a PHY domain, and an output module to induce cellular changes in response to light. A promising biotechnology tool emerged when a structure-based substitution at Asp-207 was shown to be an infrared fluorophore that uses a biologically available tetrapyrrole chromophore. We report multiple crystal structures of this D207H variant of the Deinococcus radiodurans CBD, in which His-207 is observed to form a hydrogen bond with either the tetrapyrrole A-ring oxygen or the Tyr-263 hydroxyl. Based on the implications of this duality for fluorescence properties, Y263F was introduced and shown to have stronger fluorescence than the original D207H template. Our structures are consistent with the model that the Y263F change prevents a red light-induced far-red light absorbing phytochrome chromophore configuration. With the goal of decreasing size and thereby facilitating use as a fluorescent tag in vivo, we also engineered a monomeric form of the CBD. Unexpectedly, photoconversion was observed in the monomer despite the lack of a PHY domain. This observation underscores an interplay between dimerization and the photochemical properties of phytochrome and suggests that the monomeric CBD could be used for further studies of the photocycle. The D207H substitution on its own in the monomer did not result in fluorescence, whereas Y263F did. Combined, the D207H and Y263F substitutions in the monomeric CBD lead to the brightest of our variants, designated Wisconsin infrared phytofluor (Wi-Phy). PMID:22210774

Auldridge, Michele E.; Satyshur, Kenneth A.; Anstrom, David M.; Forest, Katrina T.

2012-01-01

274

Quantification of folate in fruits and vegetables: A fluorescence-based homogeneous assay.  

PubMed

A high-throughput, homogeneous, fluorescence polarization, and fluorescence intensity assay has been developed for the measurement of folate in fruits and vegetables. This assay is based on the competitive displacement of the fluorescent folate ligands Alexa Fluor (Alexa) 594-folate and Alexa 660-folate from bovine milk folate-binding protein by folates in fruit and vegetable extracts. These fluorescent ligands are employed because their excitation and emission maxima are in regions of the spectrum with minimal autofluorescence in many extracts. Folate-binding protein and Alexa-folate were typically used at concentrations of 0.5 microg/ml and 5nM, respectively, in 20-microl volumes in 384-well microplates. The assay is complete within 100 min. The folate estimate is unaffected by the heterogeneity of polyglutamyl residues that complicates the liquid chromatography-mass spectrometry (LC-MS)-based methods of quantification. In this assay, folic acid had an apparent affinity 2.5-fold greater than 5-methyltetrahydrofolate (5MTHF); therefore, it cannot be used to quantify folate when both natural and synthetic folate are present. 5MTHF-equivalent values were measured in broccoli (240 microg/100g), strawberry (113 microg/100g), white grape (32 microg/100g), orange (44 microg/100g), tomato (12 microg/100g), raspberry (31 microg/100g), banana (29 microg/g), and kiwifruit (36 microg/100g). These data are similar to published values. However, the assay will not detect 5-formyltetrahydrofolate which is a significant constituent of the total folate in lettuce, spinach, carrot, and peppers. PMID:20361923

Martin, Harry; Comeskey, Daniel; Simpson, Robert M; Laing, William A; McGhie, Tony K

2010-07-15

275

MONITORING OF CURING PROCESS BY FLUORESCENCE TECHNIQUE. FLUORESCENCE PROBE AND LABEL BASED ON 5-DIMETHYLAMINONAPHTHALENE-1SULFONAMIDE DERIVATIVES (DNS)  

Microsoft Academic Search

The curing reaction of glycidyl ether bisphenol A (DGEBA) with n-butyl amine and\\/or N-methylethylenediamine was monitored by fluorescence spectroscopy. 5-Dimethylaminonaphthalene-1-sulfonamide (DNS) fluorophore was used as a probe and\\/or label. Fourier transform infrared (FTIR) analysis revealed that the rate constant for the addition reaction of the primary amino group hydrogen of n-butylamine to the epoxide ring is more than four times

František Mikeš; Javier González-Benito; Juan Baselga

2001-01-01

276

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

277

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

278

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

PubMed

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

2002-09-17

279

A sensitive, homogeneous fluorescence assay for detection of thymine DNA glycosylase activity based on exonuclease-mediated amplification.  

PubMed

A novel homogeneous fluorescence assay strategy for highly sensitive detection of thymine DNA glycosylase (TDG) enzyme activity based on the exonuclease-mediated signal amplification reaction was reported. PMID:23703157

Chen, Cuihua; Zhou, Dianming; Tang, Hao; Liang, Manfen; Jiang, Jianhui

2013-07-01

280

Fifth Graders' Learning About Simple Machines Through Engineering Design-Based Instruction Using LEGO™ Materials  

NASA Astrophysics Data System (ADS)

This study is part of a 5-year National Science Foundation-funded project, Transforming Elementary Science Learning Through LEGO™ Engineering Design. In this study, we report on the successes and challenges of implementing an engineering design-based and LEGO™-oriented unit in an urban classroom setting and we focus on the impact of the unit on students' content understanding of simple machines. The LEGO™ engineering-based simple machines module, which was developed for fifth graders by our research team, was implemented in an urban school in a large city in the Northeastern region of the USA. Thirty-three fifth grade students participated in the study, and they showed significant growth in content understanding. We measured students' content knowledge by using identical paper tests and semistructured interviews before and after instruction. Our paired t test analysis results showed that students significantly improved their test and interview scores (t = -3.62, p < 0.001 for multiple-choice items and t = -9.06, p < 0.000 for the open-ended items in the test and t = -12.11, p < 0.000 for the items in interviews). We also identified several alternative conceptions that are held by students on simple machines.

Marulcu, Ismail; Barnett, Mike

2012-12-01

281

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

282

A novel fluorescent sensor for mutational p53 DNA sequence detection based on click chemistry.  

PubMed

A novel fluorescent sensor for DNA sequence has been designed by taking advantages of copper nanoparticles (CuNPs) selectively formed on double stranded (ds) DNA template and Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. Copper(II) is derived from CuNPs which previously formed on the dsDNA template, and then copper(II) is reduced to copper(I) by ascorbate, which in turn induced CuAAC reaction between the weak-fluorescent compound (3-azido-7-hydroxycoumarin) and propargyl alcohol to form strong fluorescence compounds (1,2,3-triazole compounds). Since CuNPs are accumulated efficiently in the major groove of dsDNA and ssDNA has no groove, it indicates that the proposed sensor owns the merits of low detection limit, high sensitivity and selectivity for mutational p53 sequence detection. Additionally, the method has been successfully applied to recognize the sequence which contains a single-base mismatch in the short human p53 gene fragment. Furthermore, it has also been applied to detect DNA sequence in complex medium (hela cellular homogenate) with satisfactory results. PMID:23021842

Qiu, Suyan; Li, Xianghui; Xiong, Wenming; Xie, Lidan; Guo, Longhua; Lin, Zhenyu; Qiu, Bin; Chen, Guonan

2013-03-15

283

Fiber optic-based fluorescence detection system for in vivo studies of exogenous chromophore pharmacokinetics  

NASA Astrophysics Data System (ADS)

The detection and quantification of the concentration of exogenous chromophores in-vivo by their fluorescence is complicated by many physical and geometrical parameters. Measurement of such signals is advantageous in determining the pharmacokinetics of photosensitizers such as those used in photodynamic therapy (PDT) or to assist in the diagnosis of tissue histological state. To overcome these difficulties a ratio based fiber optic contact fluorometer has been developed. This fluorescence detection system (FDS) uses the ratio of the fluorescence emission peak of the exogenous chromophore to that of endogenous chromophores, i.e. autofluorescence, to correct for a variety of parameters affecting the magnitude of the measured signals. By doing so it also minimizes the range of baseline measurements prior to exogenous drug injection, for various tissue types. Design of the FDS and results of its testing in animals and patients using the second generation photosensitizer Tin ethyletiopurpurin (SnET2) are presented. These results support the feasibility and usefulness of the Ratio FDS system.

Doiron, Daniel R.; Dunn, J. B.; Mitchell, W. L.; Dalton, Brian K.; Garbo, Greta M.; Warner, Jon A.

1995-05-01

284

Fluoroimmunoassay for antigen based on fluorescence quenching between quantum dots and gold nanoparticles  

NASA Astrophysics Data System (ADS)

A unique, sensitive, and highly specific fluoroimmunoassay system for antigen detection using gold and quantum dot nanoparticles has been developed. The assay is based on the fluorescence quenching of quantum dots caused by gold nanoparticles coated with antibody. To demonstrate its analytical capabilities, the CdTe quantum dots were coated with anti-HBsAg monoclonal antibodies (QDs-MAb1) and gold nanoparticles coated with another anti-HBsAg monoclonal antibodies (GNPs-MAb2) which specifically bound with HBsAg could sandwich the HBsAg captured by the immunoreactions. The sandwich-type immunocomplex was formed and the fluorescence intensity of quantum dots was measured. The results showed that the fluorescence intensity of quantum dots at 570 nm was negative linear proportional to the HBsAg concentration logarithm, and the limit of detection of the HBsAg was 0.928 ng/mL. This new system can be extended to detect target molecules with matched antibodies and has broad potential applications in immunoassay and disease diagnosis.

Huang, Peng; Wang, Kan; Pandoli, Omar; Zhang, Xueqing; Gao, Feng; Shao, Jun; You, Xiaogang; He, Rong; Song, Hua; Cui, Daxiang

2010-11-01

285

The fast polarization modulation based dual-focus fluorescence correlation spectroscopy.  

PubMed

We introduce two new alternative experimental realizations of dual focus fluorescence correlation spectroscopy (2fFCS), a method which allows for obtaining absolute diffusion coefficient of fast moving fluorescing molecules at nanomolar concentrations, based on fast polarization modulation of the excitation beam by a resonant electro-optical modulator. The first approach rotates every second linearly polarized laser pulse by 90 degrees to obtain independent intensity readout for both foci, similar to original design. The second approach combines polarization modulation of cw laser and fluorescence lifetime correlation spectroscopy (FLCS) like analysis to obtain clean correlation curves for both overlapping foci. We tested our new approaches with different lasers and samples, revealed a need for intensity cross-talk corrections by comparing the methods with each other and discussed experimental artifacts stemming from improper polarization alignment and detector afterpulsing. The advantages of our solutions are that the polarization rotation approach requires just one pulsed laser for each wavelength, that the polarization modulation approach even mitigates the need of pulsed lasers by using standard cw lasers and that it allows the DIC prism to be placed at an arbitrary angle. As a consequence the presented experimental solutions for 2fFCS can be more easily implemented into commercial laser scanning microscopes. PMID:24515048

Štefl, Martin; Benda, Aleš; Gregor, Ingo; Hof, Martin

2014-01-13

286

Optical tweezers and non-ratiometric fluorescent-dye-based studies of respiration in sperm mitochondria  

NASA Astrophysics Data System (ADS)

The purpose of this study is to investigate how the mitochondrial membrane potential affects sperm motility using laser tweezers and a non-ratiometric fluorescent probe, DiOC6(3). A 1064 nm Nd:YVO4 continuous wave laser was used to trap motile sperm at a power of 450 mW in the trap spot. Using customized tracking software, the curvilinear velocity (VCL) and the escape force from the laser tweezers were measured. Human (Homo sapiens), dog (Canis lupis familiaris) and drill (Mandrillus leucophaeus) sperm were treated with DiOC6(3) to measure the membrane potential in the mitochondria-rich sperm midpieces. Sperm from all three species exhibited an increase in fluorescence when treated with the DiOC6(3). When a cyanide inhibitor (CCCP) of aerobic respiration was applied, sperm of all three species exhibited a reduction in fluorescence to pre-dye levels. With respect to VCL and escape force, the CCCP had no effect on dog or human sperm, suggesting a major reliance upon anaerobic respiration (glycolysis) for ATP in these two species. Based on the preliminary study on drill sperm, CCCP caused a drop in the VCL, suggesting potential reliance on both glycolysis and aerobic respiration for motility. The results demonstrate that optical trapping in combination with DiOC6(3) is an effective way to study sperm motility and energetics.

Chen, Timothy; Shi, Linda Z.; Zhu, Qingyuan; Chandsawangbhuwana, Charlie; Berns, Michael W.

2011-04-01

287

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

288

A universal fluorescence sensing strategy based on biocompatible graphene quantum dots and graphene oxide for the detection of DNA  

NASA Astrophysics Data System (ADS)

A novel and efficient fluorescence sensing platform based on biocompatible graphene quantum dots and graphene oxide was established. It showed high selectivity and sensitivity for DNA detection.A novel and efficient fluorescence sensing platform based on biocompatible graphene quantum dots and graphene oxide was established. It showed high selectivity and sensitivity for DNA detection. Electronic supplementary information (ESI) available: XPS, FTIR spectra and experimental details. See DOI: 10.1039/c3nr06583a

Qian, Z. S.; Shan, X. Y.; Chai, L. J.; Ma, J. J.; Chen, J. R.; Feng, H.

2014-05-01

289

Influence of base stacking and hydrogen bonding on the fluorescence of 2-aminopurine and pyrrolocytosine in nucleic acids.  

PubMed

Fluorescent nucleobase analogues are used extensively to probe the structure and dynamics of nucleic acids. The fluorescence of the adenine analogue 2-aminopurine and the cytosine analogue pyrrolocytosine is significantly quenched when the bases are located in regions of double-stranded nucleic acids. To allow more detailed structural information to be obtained from fluorescence studies using these bases, we have studied the excited-state properties of the bases at the CIS and TDB3LYP level in hydrogen-bonded and base-stacked complexes. The results reveal that the first excited state (the fluorescent state) of a hydrogen-bonded complex containing 2-aminopurine and thymine is just the first excited state of 2-aminopurine alone. However, the same cannot be said for structures in which 2-aminopurine is base stacked with other nucleobases. Stacking causes the molecular orbitals involved in the fluorescence transition to spread over more than one base. The predicted rate for the fluorescence transition is reduced, thus reducing the fluorescence quantum yield. The decrease in radiative rate varies with the stacking arrangement (e.g., A- or B-form DNA) and with the identity of the nucleobase with which 2-aminopurine is stacked. Stacking 2-aminopurine between two guanine moieties is shown to significantly decrease the energy gap between the first and second excited states. We do not find reliable evidence for a low-energy charge-transfer state in any of the systems that were studied. In the case of pyrrolocytosine, base stacking was found to reduce the oscillator strength for the fluorescence transition, but very little spreading of molecular orbitals across more than one base was observed. PMID:16866360

Hardman, Samantha J O; Thompson, Katherine C

2006-08-01

290

Optimizing two radioluminescence based quality assurance devices for diagnostic radiology utilizing a simple model  

NASA Astrophysics Data System (ADS)

The extrinsic (absolute) efficiency of a phosphor is expressed as the ratio of light energy emitted per unit area at the phosphor surface to incident x-ray energy fluence. A model described in earlier work has shown that by knowing the intrinsic efficiency, the particle size, the thickness and the light extinction factor ?, it is possible to deduce the extrinsic efficiency for an extended range of particle sizes and layer thicknesses for a given design. The model has been tested on Gd2O2S:Tb and ZnS:Cu fluorescent layers utilized in two quality assurance devices, respectively, aimed for the assessment of light field and radiation field congruence in diagnostic radiology. The first unit is an established device based on both fluorescence and phosphorescence containing an x-ray sensitive phosphor (ZnS:Cu) screen comprising a long afterglow. Uncertainty in field edge position is estimated to 0.8 mm (k=2). The second unit is under development and based on a linear CCD sensor which is sensitized to x-rays by applying a Gd2O2S:Tb scintillator. The field profiles and the corresponding edge location are then obtained and compared. Uncertainty in field edge location is estimated to 0.1 mm (k=2). The properties of the radioluminescent layers are essential for the functionality of the devices and have been optimized utilizing the previously developed and verified model. A theoretical description of the maximization of phosphorescence is also briefly discussed as well as an interesting finding encountered during the development processes: focal spot wandering. The oversimplistic physical assumptions made in the radioluminescence model have not been found to lead the optimizing process astray. The obtained functionality is believed to be adequate within their respective limitations for both devices.

Lindström, Jan; Hulthén, Markus; Alm Carlsson, Gudrun; Sandborg, Michael

2014-03-01

291

A simple filter-based approach to surface enhanced Raman spectroscopy for trace chemical detection.  

PubMed

We demonstrate an extremely simple and practical surface enhanced Raman spectroscopy (SERS) technique for trace chemical detection. Filter membranes first trap silver nanoparticles to form a SERS-active substrate and then concentrate analytes from a mL-scale sample into a ?L-scale detection volume. We demonstrate a significant improvement in detection limit as compared to colloidal SERS for the pesticide malathion and the food contaminant melamine. The measured SERS intensity exhibits low variation relative to traditional SERS techniques, and the data can be closely fit with a Langmuir isotherm. Thus, due to the simple procedure, the low-cost of the substrates, the quantitative results, and the performance improvement due to analyte concentration, our technique enables SERS to be practical for a broad range of analytical applications, including field-based detection of toxins in large-volume samples. PMID:22282766

Yu, Wei W; White, Ian M

2012-03-01

292

Combination of adhesive-tape-based sampling and fluorescence in situ hybridization for rapid detection of Salmonella on fresh produce.  

PubMed

This protocol describes a simple approach for adhesive-tape-based sampling of tomato and other fresh produce surfaces, followed by on-tape fluorescence in situ hybridization (FISH) for rapid culture-independent detection of Salmonella spp. Cell-charged tapes can also be placed face-down on selective agar for solid-phase enrichment prior to detection. Alternatively, low-volume liquid enrichments (liquid surface miniculture) can be performed on the surface of the tape in non-selective broth, followed by FISH and analysis via flow cytometry. To begin, sterile adhesive tape is brought into contact with fresh produce, gentle pressure is applied, and the tape is removed, physically extracting microbes present on these surfaces. Tapes are mounted sticky-side up onto glass microscope slides and the sampled cells are fixed with 10% formalin (30 min) and dehydrated using a graded ethanol series (50, 80, and 95%; 3 min each concentration). Next, cell-charged tapes are spotted with buffer containing a Salmonella-targeted DNA probe cocktail and hybridized for 15 - 30 min at 55°C, followed by a brief rinse in a washing buffer to remove unbound probe. Adherent, FISH-labeled cells are then counterstained with the DNA dye 4',6-diamidino-2-phenylindole (DAPI) and results are viewed using fluorescence microscopy. For solid-phase enrichment, cell-charged tapes are placed face-down on a suitable selective agar surface and incubated to allow in situ growth of Salmonella microcolonies, followed by FISH and microscopy as described above. For liquid surface miniculture, cell-charged tapes are placed sticky side up and a silicone perfusion chamber is applied so that the tape and microscope slide form the bottom of a water-tight chamber into which a small volume (? 500 ?L) of Trypticase Soy Broth (TSB) is introduced. The inlet ports are sealed and the chambers are incubated at 35 - 37°C, allowing growth-based amplification of tape-extracted microbes. Following incubation, inlet ports are unsealed, cells are detached and mixed with vigorous back and forth pipetting, harvested via centrifugation and fixed in 10% neutral buffered formalin. Finally, samples are hybridized and examined via flow cytometry to reveal the presence of Salmonella spp. As described here, our "tape-FISH" approach can provide simple and rapid sampling and detection of Salmonella on tomato surfaces. We have also used this approach for sampling other types of fresh produce, including spinach and jalapeño peppers. PMID:21048665

Bisha, Bledar; Brehm-Stecher, Byron F

2010-01-01

293

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

294

Homogeneous immunoassays based on fluorescence emission intensity variations of zinc selenide quantum dot sensors.  

PubMed

The fluorescence emission intensity of ZnSe quantum dots (QDs) conjugated to proteins to form QD-based biomolecular sensors increases significantly upon binding of the sensors to target proteins in solution. This phenomenon enables the development of homogeneous, separation-free immunoassays for rapid quantitative detection of proteins in solution. Proof-of-principle assays were developed by dosing a solution containing a biomolecular target with a solution containing the corresponding QD-based sensor and monitoring the changes in the peak fluorescence emission intensity of the QDs. Direct immunoassays for detecting basic fibroblast growth factor (bFGF) and prostate-specific antigen (PSA) in solution were demonstrated using QD-anti-bFGF and QD-anti-PSA sensors. A competitive immunoassay for detecting human serum albumin (HSA) was also demonstrated by dosing samples containing HSA with QD-HSA sensors and free anti-HSA antibodies. The QD-HSA sensors were tested in 1000× diluted human serum and found to be unaffected by interference from other proteins. The lower limit of detection of the assays was equal to the lowest sensor concentration in the solution that can be unambiguously detected, typically less than 1 nM. The dynamic range of the assays was determined by identifying the sensor concentration above which optical interference between QDs affected adversely the observed fluorescence emission intensity. The upper limit of this concentration was 2.5 ?M for 4 nm QDs. The ZnSe QD-based sensors were stable and preserved ~80% of their initial peak emission intensity after two months in refrigerated storage. These biosensors have potential applications in rapid sensing of target proteins for emergency and point-of-care diagnostic applications. PMID:22960008

Wang, Jun; Mountziaris, T J

2013-03-15

295

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

296

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

297

Prototype imaging x-ray fluorescence spectrometer based on microchannel plate optics  

NASA Astrophysics Data System (ADS)

A new form of imaging x-ray fluorescence spectrometer, based on a microchannel plate relay optic and a charge coupled device x-ray detector, produces elemental mapping over an instantaneous field of view of 24 mm square without the need to scan either the sample or x-ray beam. We describe the design of a prototype responsive over the energy range of 370 eV-10 keV, its quantitative calibration, demonstration of 0.7 mm spatial resolution and the spectrometer's use in the analysis of geological samples.

Price, G. J.; Fraser, G. W.; Pearson, J. F.; Nussey, J. P.; Hutchinson, I. B.; Holland, A. D.; Turner, K.; Pullan, D.

2004-07-01

298

Fluorescent refrigeration  

DOEpatents

Fluorescent refrigeration is based on selective radiative pumping, using substantially monochromatic radiation, of quantum excitations which are then endothermically redistributed to higher energies. Ultimately, the populated energy levels radiatively deexcite emitting, on the average, more radiant energy than was initially absorbed. The material utilized to accomplish the cooling must have dimensions such that the exciting radiation is strongly absorbed, but the fluorescence may exit the material through a significantly smaller optical pathlength. Optical fibers and mirrored glasses and crystals provide this requirement.

Epstein, Richard I. (Santa Fe, NM); Edwards, Bradley C. (Los Alamos, NM); Buchwald, Melvin I. (Santa Fe, NM); Gosnell, Timothy R. (Santa Fe, NM)

1995-01-01

299

A simple method for monitoring changes in cell height using fluorescent microbeads and an Ussing-type chamber for the inverted microscope  

Microsoft Academic Search

In this study, we report two developments for studies of ion transport in cultured epithelial cells. First, a convenient method is presented for measuring apparent cell height using fluorescent microbeads as high-contrast landmarks of the apical and basal cell surfaces. The apparent cell height is then used as an indicator to monitor the time course of changes in cell volume

William E. Crowe; Nancy K. Wills

1991-01-01

300

High performance magnesium anode in paper-based microfluidic battery, powering on-chip fluorescence assay.  

PubMed

A high power density and long-lasting stable/disposable magnesium battery anode was explored for a paper-based fluidic battery to power on-chip functions of various Point of Care (POC) devices. The single galvanic cell with magnesium foil anode and silver foil cathode in Origami cellulose chip provided open circuit potential, 2.2?V, and power density, 3.0 mW/cm(2). A paper-based fluidic galvanic cell was operated with one drop of water (80 ?l) and continued to run until it was dry. To prove the concept about powering on-chip POC devices, two-serial galvanic cells are developed and incorporated with a UV-light emitting diode (??=?365?nm) and fluorescence assay for alkaline phosphatase reaction. Further, detection using smart phones was performed for quantitative measurement of fluorescent density. To conclude, a magnesium-based fluidic battery paper chip was extremely low-cost, required minute sample volumes, was easy to dispose of, light weight, easy to stack, store and transport, easy to fabricate, scalable, and has faster analysis times. PMID:25332741

Koo, Youngmi; Sankar, Jagannathan; Yun, Yeoheung

2014-09-01

301

A boronic-acid-based probe for fluorescence polarization assays with penicillin binding proteins and ?-lactamases.  

PubMed

Penicillin binding proteins (PBPs) and ?-lactamases are involved in interactions with ?-lactam antibiotics connected with both antibacterial activity and mediation of bacterial ?-lactam resistance. Current methods for identifying inhibitors of PBPs and ?-lactamases can be inefficient and are often not suitable for studying weakly and/or reversibly binding compounds. Therefore, improved ligand binding assays for PBPs and ?-lactamases are needed. We report the development of a fluorescence polarization (FP) assay for PBPs and "serine" ?-lactamases using a boronic-acid-based, reversibly binding "tracer." The tracer was designed based on a crystal structure of a covalent complex between a boronic acid and PBP1b from Streptococcus pneumoniae. The tracer bound to three different PBPs with modest affinity (K(d)=4-12 ?M) and more tightly to the TEM1 serine ?-lactamase (K(d)=109 nM). ?-Lactams and other boronic acids were able to displace the tracer in competition assays. These results indicate that fluorescent boronic acids are suited to serve as reversibly binding tracers in FP-based assays with PBPs and ?-lactamases and potentially with other related enzymes. PMID:21925482

Inglis, Steven R; Strieker, Matthias; Rydzik, Anna M; Dessen, Andréa; Schofield, Christopher J

2012-01-01

302

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

303

The Circadian Energy Scale (CIRENS): two simple questions for a reliable chronotype measurement based on energy.  

PubMed

This study presents the Circadian Energy Scale (CIRENS), a very short and simple chronotype measurement tool based on energy. The CIRENS consists of two introspective questions about the usual energy level (very low, low, moderate, high, or very high, scored 1 to 5) in the morning and in the evening. The difference between energy level scores (-4 to 4) felt by respondents in the evening and morning defines the chronotype score and classification. A concurrent validity analysis of the CIRENS with the widely used Horne and Östberg Morningness-Eveningness Questionnaire (MEQ) was conducted using a sample of 225 college students, and with MSFsc, a sleep-based chronotype assessment tool based on the Munich Chronotype Questionnaire (MCTQ), using a sample of 34,530 subjects (18-83 yrs, 27% males). This large sample was collected in a Web survey for behavioral correlates of the CIRENS with variables previously associated with chronotype differences. The correlation of the CIRENS chronotype score was r?=?-.70 with the MEQ and r?=?.32 with the MSFsc. CIRENS chronotype scores declined with age and were not affected by sex. Both CIRENS and MSFsc chronotype scores were related to differences in tobacco, caffeine, and cola soft-drink consumption (all higher in evening types). The CIRENS provides a simple chronotype index and a measure of absolute energy throughout the day and seems to be a reliable chronotype assessment tool that may be useful both clinically and for large-scale studies. PMID:21452918

Ottoni, Gustavo L; Antoniolli, Eduardo; Lara, Diogo R

2011-04-01

304

TDDFT study on the sensing mechanism of a fluorescent sensor based on Sisbnd O bond for fluoride anion  

NASA Astrophysics Data System (ADS)

The sensing mechanism of a reported fluorescent sensor based on Sisbnd O bond for fluoride was studied by (TD)DFT calculations. The reaction energy of fluoride is calculated to be the lowest among various anions, indicating the high selectivity of this sensor. The structures were confirmed by geometry optimizations and scanning potential-energy curves. This sensor could emit strong fluorescence by its local S1-S0 transition. The phenolate anion would change its structure at the S1 state, decreasing its energy and emitting weak fluorescence, which is resulted by a photoinduced electron transfer process.

Li, Guang-Yue; Wang, Jie-Ping; Zhang, Hang; Li, Wei-Wei; Wang, Feng; Liang, Ying-Hua

2014-11-01

305

Supramolecular solvent-based microextraction of ochratoxin A in raw wheat prior to liquid chromatography-fluorescence determination.  

PubMed

A supramolecular solvent made up of reverse micelles of decanoic acid, dispersed in a continuous phase of THF:water, was proposed for the simple, fast and efficient microextraction of OTA in wheat prior to liquid chromatography-fluorescence determination. The method involved the stirring of 300 mg-wheat subsamples (particle size 50microm) and 350microL of supramolecular solvent for 15min, subsequent centrifugation for 15min and the direct quantitation of OTA in the extract, previous 5.7-fold dilution with ethanol/water/acetic acid (49.5/49.5/1), against solvent-based calibration curves. No clean-up of the extracts or solvent evaporation was needed. Interactions between the supramolecular solvent and major matrix components in the wheat (i.e. carbohydrates, lipids and proteins) were investigated. The reverse micelles in the extractant induced gluten flocculation but only in the coacervation region of lower analytical interest (i.e. at percentages of THF above 11%). The quantitation of OTA was interference-free. Representativity of the 300 mg-wheat subsamples was proved by analysing a reference material. OTA recoveries in wheat ranged between 84% and 95% and the precision of the method, expressed as relative standard deviation, was 2%. The quantitation limit of the method was 1.5microgkg(-1) and was below the threshold limit established for OTA in raw cereals by EU directives (5.0microgkg(-1)). The method developed was validated by using a certified reference material and it was successfully applied to the determination of OTA in different wheat varieties from crops harvested in the South of Spain. OTA was not detected in any of the analysed samples. This method allows quick and simple microextraction of OTA with minimal solvent consumption, while delivering accurate and precise data. PMID:19932484

García-Fonseca, Sergio; Ballesteros-Gómez, Ana; Rubio, Soledad; Pérez-Bendito, Dolores

2010-04-16

306

Vesicular aggregate-based solventless microextraction of Ochratoxin A in dried vine fruits prior to liquid chromatography and fluorescence detection.  

PubMed

A solventless microextraction was proposed for the development of a simple, fast, low-cost and environmental friendly sample treatment for the determination of Ochratoxin A (OTA) in dried vine fruits. The objective was to offer an alternative to conventional sample treatments, which invariably involve extractions with large solvent volumes followed by clean-up with expensive, not recyclable and limited storage stability immunoaffinity sorbents. The method involved the stirring of 300 mg of dried vine fruit subsamples with 400 ?L of a supramolecular solvent (SUPRAS) made up of decanoico acid/tetrabutylammonium decanoate vesicles. Then, the sample was centrifuged for 15 min and OTA was quantified in the extract by liquid chromatography/fluorescence detection against solvent-based calibration curves. Neither dilution nor further clean-up steps of extracts were needed. Quantitation of OTA was interference-free and recoveries ranged between 95% and 101%. The precision of the method, expressed as relative standard deviation (RSD), was about 3%. The limit of quantification (5.3 ?g kg(-1)) was below the threshold limit established for OTA in dried vine fruits by EU directives (10 ?g kg(-1)). Representativity of subsamples was proven. The method was successfully applied to the analysis of several dried vine fruits (sultanas and muscatels) purchased in local supermarkets in Córdoba (South of Spain). OTA was not detected in any of the analyzed samples. This solventless sample treatment allows quick and simple microextraction of OTA, while delivering accurate and precise data, and extends the range of eco-friendly methods in labs. PMID:22284505

Caballero-Casero, Noelia; García-Fonseca, Sergio; Rubio, Soledad

2012-01-30

307

Quick and simple sample treatment for multiresidue analysis of bisphenols, bisphenol diglycidyl ethers and their derivatives in canned food prior to liquid chromatography and fluorescence detection.  

PubMed

We report herein a multiresidue method for canned food determination of 12 bisphenols [bisphenol A (BPA), bisphenol B (BPB), bisphenol F (BPF), bisphenol E (BPE)], bisphenol diglycidyl ethers [bisphenol F diglycidyl ether (BFDGE), bisphenol A diglycidyl ether (BADGE)] and their derivatives [BADGE·2H2O, BADGE·H2O, BADGE·HCl·H2O, BADGE·HCl, BADGE·2HCl and BFDGE·2HCl]. The method was based on the microextraction of the target contaminants in 200mg food sample with 600 ?L of a supramolecular solvent made up of inverse aggregates of tetradecanol, followed by analysis of the extract by liquid chromatography/fluorescence detection using external calibration. Chromatographic separation of all target compounds, including the ortho-ortho, ortho-para and para-para isomers of BFDGE and BFDGE·2HCl, was achieved with baseline separation (Resolution ? 1.52). No concentration of the extracts was required, the microextraction took about 30 min and several samples could be simultaneous treated. Method validation was carried out according to the recommendations of the European Commission Decision 2002/657/EC. Quantitation limits for the different analytes ranged between 0.9 and 3.5 ?g kg(-1). Repeatability and reproducibility, expressed as relative standard deviation, were in the ranges 1.8-6.8% and 4.4-8.1%. The method was applied to the analysis of the target compounds in different food categories including vegetables, legumes, fruits, fish and seafood, meat product and grain. Recoveries in samples were within the range 80-110%. Only BPF and BPE were undetected in the canned food analyzed. The concentration found for the rest of bisphenols, diglycidyl ethers and derivatives was in the range 7.1-959 ?g kg(-1). The study of the isomeric distribution of BFDGE and BFDGE·2HCl in food showed that they are preferentially present as one of the isomeric forms, that highlighting for further studies. The analytical and operational characteristics of this multiresidue method make it suitable for monitoring programs intended for the assessment of human exposure to bisphenols, diglycidyl ethers and derivatives from diet. PMID:24594089

Alabi, A; Caballero-Casero, N; Rubio, S

2014-04-01

308

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

309

A new pyrene based highly sensitive fluorescence probe for copper(II) and fluoride with living cell application.  

PubMed

A new pyrene based fluorescence probe has been synthesized for fluorogenic detection of Cu(2+) in acetonitrile-aqueous media (7?:?3 CH3CN-HEPES buffer, v/v, at pH 7.5) with bioimaging in both prokaryotic (Candida albicans cells) and eukaryotic (Tecoma stans pollen cells) living cells. The anion recognition properties of the sensor have also been studied in acetonitrile by fluorescence methods which show remarkable sensitivity toward fluoride over other anions examined. PMID:24671378

Goswami, Shyamaprosad; Chakraborty, Shampa; Paul, Sima; Halder, Sandipan; Panja, Sukanya; Mukhopadhyay, Subhra Kanti

2014-05-21

310

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

311

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

312

Selective visualization of fluorescent sterols in Caenorhabditis elegans by bleach-rate-based image segmentation.  

PubMed

The nematode Caenorhabditis elegans is a genetically tractable model organism to investigate sterol transport. In vivo imaging of the fluorescent sterol, dehydroergosterol (DHE), is challenged by C. elegans' high autofluorescence in the same spectral region as emission of DHE. We present a method to detect DHE selectively, based on its rapid bleaching kinetics compared to cellular autofluorescence. Worms were repeatedly imaged on an ultraviolet-sensitive wide field (UV-WF) microscope, and bleaching kinetics of DHE were fitted on a pixel-basis to mathematical models describing the intensity decay. Bleach-rate constants were determined for DHE in vivo and confirmed in model membranes. Using this method, we could detect enrichment of DHE in specific tissues like the nerve ring, the spermateca and oocytes. We confirm these results in C. elegans gut-granule-loss (glo) mutants with reduced autofluorescence and compare our method with three-photon excitation microscopy of sterol in selected tissues. Bleach-rate-based UV-WF imaging is a useful tool for genetic screening experiments on sterol transport, as exemplified by RNA interference against the rme-2 gene coding for the yolk receptor and for worm homologues of Niemann-Pick C disease proteins. Our approach is generally useful for identifying fluorescent probes in the presence of high cellular autofluorescence. PMID:20070610

Wüstner, Daniel; Landt Larsen, Ane; Faergeman, Nils J; Brewer, Jonathan R; Sage, Daniel

2010-04-01

313

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

314

Highly sensitive fluorescence optode based on polymer inclusion membranes for determination of Al(III) ions.  

PubMed

This paper reports the use of a polymer inclusion membranes (PIMs) for direct determination of Al(III) ions in natural water by using a fluorescence based optode. The best composition of the PIMs consisted of 60 wt.% (m/m) poly (vinyl chloride) (PVC) as the base polymer, 20 wt.% (m/m) triton X-100 as an extractant, 20 wt.% (m/m) dioctyl phthalate (DOP) as plasticizer and morin as the reagent, was used in this study. The inclusion of triton X-100 was used for enhancing the sorption of Al(III) ions from liquid phase into the membrane phase, thus increasing the optode fluorescence intensity. The optimized optode was characterized by a linear calibration curve in the range from 7.41?×?10(-7) to 1.00?×?10(-4) molL(-1) of Al(III), with a detection limit of 5.19?×?10(-7) molL(-1). The response of the optode was 4 min and reproducible results were obtained for eight different membranes demonstrated good membrane stability. The optode was applied to the determination of Al(III) in natural water samples. The result obtained is comparable to atomic absorption spectrometry method. PMID:24871034

Suah, F B M; Ahmad, M; Heng, L Y

2014-07-01

315

Development of a Pterin-based Fluorescent Probe for Screening Dihydropteroate Synthase  

PubMed Central

Dihydropteroate synthase (DHPS) is the classical target of the sulfonamide class of antimicrobial agents, whose use has been limited by widespread resistance and pharmacological side effects. We have initiated a structure-based drug design approach for the development of novel DHPS inhibitors that bind to the highly conserved and structured pterin sub-site rather than to the adjacent p-amino benzoic acid binding pocket that is targeted by the sulfonamide class of antibiotics. To facilitate these studies, a robust pterin site-specific fluorescence polarization (FP) assay has been developed and is discussed herein. These studies include the design, synthesis and characterization of two fluorescent probes, and the development and validation of a rapid DHPS FP assay. This assay has excellent DMSO tolerance and is highly reproducible as evidenced by a high Z’ factor. This assay offers significant advantages over traditional radiometric or phosphate release assays against this target, and is suitable for site-specific high throughput and fragment-based screening studies. PMID:21916405

Zhao, Ying; Hammoudeh, Dalia; Lin, Wenwei; Das, Sourav; Yun, Mi-Kyung; Li, Zhenmei; Griffith, Elizabeth; Chen, Taosheng; White, Stephen W.; Lee, Richard E.

2011-01-01

316

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

317

Sensitive Pb(2+) probe based on the fluorescence quenching by graphene oxide and enhancement of the leaching of gold nanoparticles.  

PubMed

A novel strategy was developed for fluorescent detection of Pb(2+) in aqueous solution based on the fact that graphene oxide (GO) could quench the fluorescence of amino pyrene (AP)-grafted gold nanoparticles (AP-AuNPs) and Pb(2+) could accelerate the leaching rate of AuNPs in the presence of S2O3(2-). In this system, fluorescence reporter AP was grafted on AuNPs through the Au-N bond. In the presence of GO, the system shows fluorescence quenching because of ?-? stacking between AP and GO. With the addition of Pb(2+) and S2O3(2-), the system displays fluorescence recovery, which is attributed to the fact that Pb(2+) could accelerate the leaching of the AuNPs from GO surfaces and release of AP into aqueous solution. Interestingly, the concentration of GO could control the fluorescence "turn-off" or "turn-on" for Pb(2+) detection. In addition, GO is also an excellent promoter for the acceleration of the leaching of AuNPs and shortening the analytical time to ?15 min. Under the optimal conditions, the fluorescence Pb(2+) sensor shows a linear range from 2.0 × 10(-9) to 2.3 × 10(-7) mol/L, with a detection limit of 1.0 × 10(-10) mol/L. PMID:24476458

Shi, Xinhao; Gu, Wei; Peng, Weidong; Li, Bingyu; Chen, Ningning; Zhao, Kai; Xian, Yuezhong

2014-02-26

318

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

319

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

320

Molecularly imprinted polymer based on CdTe@SiO2 quantum dots as a fluorescent sensor for the recognition of norepinephrine.  

PubMed

A novel molecular imprinted sensor based on CdTe@SiO2 quantum dots (QDs) was developed for norepinephrine (NE) recognition. The molecularly imprinted polymer (MIP) on the surface of CdTe@SiO2 QDs (CdTe@SiO2@MIP) was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and fluorescence spectroscopy. The synthesized nanosensor had a distinguished selectivity and high binding affinity to NE. Under optimal conditions, the relative fluorescence intensity of CdTe@SiO2@MIP linearly decreased with increase of the concentration of NE in the range of 0.04-10 ?M. The limit of detection was 8 nM (3?/K). The proposed method was applied to the analysis of NE in rat plasma, and the result obtained by the method was in good agreement with that assayed by the fluorescence derivatization method. The method developed is simple, fast, and can be applied to the determination of NE in biological samples. PMID:25148475

Wei, Fangdi; Wu, Yanzi; Xu, Guanhong; Gao, Yankun; Yang, Jing; Liu, Liping; Zhou, Ping; Hu, Qin

2014-10-15

321

Absorption and Fluorescence Signatures of 1,2,3-Triazole Based Re-gioisomers : Challenging Compounds for TD-DFT  

E-print Network

Absorption and Fluorescence Signatures of 1,2,3-Triazole Based Re- gioisomers : Challenging two model regioisomers based on the 1,2,3-triazole moiety. Starting from their experimental absorption obtained for 1,2,3-triazole based chromophores need to be treated with caution. We also show that the SS

Recanati, Catherine

322

Polymer-and Glass-based Fluorescence Standards for the Near Infrared (NIR) Spectral Region  

Microsoft Academic Search

The widespread use and acceptance of fluorescence techniques especially in regulated areas like medical diagnostics is closely\\u000a linked to standardization concepts that guarantee and improve the comparability and reliability of fluorescence measurements.\\u000a At the core of such concepts are dependable fluorescence standards that are preferably certified. The ever rising interest\\u000a in fluorescence measurements in the near-infrared (NIR) spectral region renders

Christian Würth; Katrin Hoffmann; Thomas Behnke; Marius Ohnesorge; Ute Resch-Genger

2011-01-01

323

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

324

Simple paper-based test for measuring blood hemoglobin concentration in resource-limited settings  

PubMed Central

Background The measurement of hemoglobin concentration ([Hb]) is performed routinely as a part of a complete blood cell count to evaluate the oxygen-carrying capacity of blood. Devices currently available to physicians and clinical laboratories for measuring [Hb] are accurate, operate on small samples and provide results rapidly, but may be prohibitively expensive for resource-limited settings. The unavailability of accurate but inexpensive diagnostic tools often precludes proper diagnosis of anemia in low-income developing countries. Therefore, we developed a simple paper-based assay for measuring [Hb]. Methods A 20-?L droplet of a mixture of blood and Drabkin’s reagent was deposited onto patterned chromatography paper. The resulting blood stain was digitized with a portable scanner and analyzed. The mean color intensity of the blood stain was used to quantify [Hb]. We compared the performance of the paper-based Hb assay with a hematology analyzer (comparison method) using blood samples from 54 subjects. Results The values of [Hb] measured using the paper-based assay and the comparison method were highly correlated (R2 = 0.9598); the standard deviation of the difference between the two measurements was 0.62 g/dL. The assay was accurate within 1 g/dL 90.7% of the time, overestimating [Hb] by ?1 g/dL in 1.9% and underestimating [Hb] by ?1 g/dL in 7.4% of the subjects. Conclusions This study demonstrates the feasibility of the paper-based Hb assay. This simple, low-cost test should be useful for diagnosing anemia in resource-limited settings, particularly in the context of care for malaria, HIV and sickle cell disease patients in sub-Saharan Africa. PMID:23788584

Yang, Xiaoxi; Piety, Nathaniel Z.; Vignes, Seth M.; Benton, Melody S.; Kanter, Julie; Shevkoplyas, Sergey S.

2013-01-01

325

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

326

High-resolution deep imaging of live cellular spheroids with light-sheet-based fluorescence microscopy.  

PubMed

Conventional two-dimensional cell monolayers do not provide the geometrical, biochemical and mechanical cues found in real tissues. Cells in real tissues interact through chemical and mechanical stimuli with adjacent cells and via the extracellular matrix. Such a highly interconnected communication network extends along all three dimensions. This architecture is lost in two-dimensional cultures. Therefore, at least in many cases, two-dimensional cell monolayers do not represent a suitable in vitro tool to characterize accurately the biology of real tissues. Many studies performed over the last few years have demonstrated that the differences between three-dimensional and two-dimensional cultured cells are striking at the morphological and molecular levels and that three-dimensional cell cultures can be employed in order to shrink the gap between real tissues and in vitro cell models. End-point and long-term imaging of cellular and sub-cellular processes with fluorescence microscopy provides direct insight into the physiological behavior of three-dimensional cell cultures and their response to chemical or mechanical stimulation. Fluorescence imaging of three-dimensional cell cultures sets new challenges and imposes specific requirements concerning the choice of a suitable microscopy technique. Deep penetration into the specimen, high imaging speed and ultra-low intensity of the excitation light are key requirements. Light-sheet-based fluorescence microscopy (LSFM) offers a favorable combination of these requirements and is therefore currently established as the technique of choice for the study of three-dimensional cell cultures. This review illustrates the benefits of cellular spheroids in the life sciences and suggests that LSFM is essential for investigations of cellular and sub-cellular dynamic processes in three-dimensions over time and space. PMID:23443300

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

2013-04-01

327

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

328

Overcoming the aggregation problem: a new type of fluorescent ligand for ConA-based glucose sensing.  

PubMed

Competitive binding assays based on the lectin Concanavalin A (ConA) have displayed significant potential to serve in continuous glucose monitoring applications. However, to date, this type of fluorescent, affinity-based assay has yet to show the stable, glucose predictive capabilities that are required for such an application. This instability has been associated with the extensive crosslinking between traditionally-used fluorescent ligands (presenting multiple low-affinity moieties) and ConA (presenting multiple binding sites) in free solution. The work herein introduces the design and synthesis of a new type of fluorescent ligand that can avoid this aggregation and allow the assay to be sensitive across the physiologically relevant glucose concentration range. This fluorescent ligand (APTS-MT) presents a single high-affinity trimannose moiety that is recognized by ConA's full binding site and a fluorophore that can effectively track the ligand's equilibrium binding via fluorescent anisotropy. This is confirmed by comparing its measured fluorescent lifetime to experimentally-determined rotational correlation lifetimes of the free and bound populations. Using an assay comprised of 200 nM APTS-MT and 1 µM ConA, the fluorescence anisotropy capably tracks the concentration of monosaccharides that are known to bind to ConA's primary binding site, and the assay displays a MARD of 6.5% across physiologically relevant glucose concentrations. Ultimately, this rationally-designed fluorescent ligand can facilitate the realization of the full potential of ConA-based glucose sensing assays and provide the basis for a new set of competing ligands to be paired with ConA. PMID:25058939

Cummins, Brian M; Li, Mingchien; Locke, Andrea K; Birch, David J S; Vigh, Gyula; Coté, Gerard L

2015-01-15

329

Design and Control of a Clutch for a Minimally-Actuated Biped Based on the Passive-Dynamic Simple Walker  

E-print Network

Walker by Arlis Reynolds SUBMITTED TO THE DEPARTMENT OF MECHANICAL ENGINEERING IN PARTIAL FULFILLMENT Based on the Passive-Dynamic Simple Walker by Arlis Reynolds Submitted to the Department of Mechanical is tested on a hip actuated simple 3D walker to evaluate the performance capabilities of clutched control

Tedrake, Russ

330

Detecting solar-induced chlorophyll fluorescence from field radiance spectra based on the Fraunhofer line principle  

Microsoft Academic Search

It is difficult to quantify the amount of chlorophyll fluorescence emitted by a leaf or canopy under natural sunlight because the reflected light obscures the fluorescence signal. In this study, two diurnal experiments were conducted on winter wheat (Triticum aestivum L.) and Japan Creeper (Parthenocissus tricuspidata) to detect the solar-induced chlorophyll fluorescence from field radiance spectra. In the separation of

Liangyun Liu; Yongjiang Zhang; Jihua Wang; Chunjiang Zhao

2005-01-01

331

Synchrotron radiation based micro X-ray fluorescence analysis of the calibration samples used in surface sensitive total reflection and grazing emission X-ray fluorescence techniques  

NASA Astrophysics Data System (ADS)

Total reflection X-ray fluorescence (TXRF) and grazing emission X-ray fluorescence (GEXRF) are surface sensitive techniques and can be used for detailed surface studies of different materials, including ultra-low concentration contamination or the lateral and depth distributions of elements. The calibration procedure typically used involves placing a micro-droplet (˜?l) of the standard solution onto a silicon wafer (or quartz backing). After evaporation of the solvent, the residual amount of elements is used as a reference standard. Knowledge of the distribution of residue material on the substrate surface is crucial for precise quantification. In the present work the investigation of the lateral distribution of elements in the multielemental calibrating samples, containing the 23 most commonly studied elements, by using the synchrotron radiation based micro X-ray fluorescence is presented. The goal of this project was the study of a uniformity of the elemental distributions and determination of the residual elements morphology depending on the temperature of the drying process. The X-ray images were compared with optical and SEM images. Paper presents in details the experimental setup, sample preparation procedures, measurements and results. In the analysis of the X-ray images of the sample dried in high temperature the censoring approach was applied improving the quality of statistical analysis. The information on the elements distribution in the calibrating samples can be useful for developing more accurate calibration procedures applied in quantitative analysis of surface sensitive TXRF and GEXRF techniques.

Kubala-Kuku?, A.; Bana?, D.; Pajek, M.; Szlachetko, J.; Jagodzi?ski, P.; Susini, J.; Salomé, M.

2013-12-01

332

Competitive binding for triggering a fluorescence response in a hydrazodicarboxamide-based [2]rotaxane.  

PubMed

The design and synthesis of an interlocked receptor based on a hydrogen bonded [2]rotaxane containing a hydrazodicarboxamide binding site are reported. An anion recognition process with tetrabutylammonium benzoate triggers the submolecular translational movement of its benzylic amide macrocycle developing a progressive increase of the fluorescence intensity, effectively quenched at the original state. The binding of the anion competes with the hydrogen-bond-connected cyclic component for the bis(urea)-based station pushing it towards a stoppered alkyl chain. Moreover, this interlocked system is able to work as a molecular switch restoring its initial state in two ways, either by an ion exchange reaction or by a high yielding oxidation/reduction sequence. PMID:24270597

Berná, José; Franco-Pujante, Carlos; Alajarín, Mateo

2014-01-21

333

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

334

Fundamental parameter based quantification algorithm for confocal nano-X-ray fluorescence analysis  

NASA Astrophysics Data System (ADS)

A new method for the quantification of X-ray fluorescence (XRF) was derived based on the fundamental parameter method (FPM). The FPM equations were adapted to accommodate the special case of confocal nano-XRF, i.e. X-ray nano-beam excitation coupled with confocal detection, taking into account the special characteristics of the detector channel polycapillary. A thorough error estimation algorithm based on the Monte Carlo method was applied, producing a detailed analysis of the uncertainties of the quantification results. The new FPM algorithm was applied on confocal nano-XRF data obtained from cometary dust returned by NASA's Stardust mission, recorded at beamline ID13 of the European Synchrotron Radiation Facility.

Schoonjans, Tom; Silversmit, Geert; Vekemans, Bart; Schmitz, Sylvia; Burghammer, Manfred; Riekel, Christian; Brenker, Frank E.; Vincze, Laszlo

2012-01-01

335

Mesh-based Monte Carlo method in time-domain widefield fluorescence molecular tomography.  

PubMed

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

2012-10-01

336

Mesh-based Monte Carlo method in time-domain widefield fluorescence molecular tomography  

NASA Astrophysics Data System (ADS)

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/.

Chen, Jin; Fang, Qianqian; Intes, Xavier

2012-10-01

337

Using Spinach-based sensors for fluorescence imaging of intracellular metabolites and proteins in living bacteria.  

PubMed

Genetically encoded fluorescent sensors can be valuable tools for studying the abundance and flux of molecules in living cells. We recently developed a novel class of sensors composed of RNAs that can be used to detect diverse small molecules and untagged proteins. These sensors are based on Spinach, an RNA mimic of GFP, and they have successfully been used to image several metabolites and proteins in living bacteria. Here we discuss the generation and optimization of these Spinach-based sensors, which, unlike most currently available genetically encoded reporters, can be readily generated to any target of interest. We also provide a detailed protocol for imaging ADP dynamics in living Escherichia coli after a change from glucose-containing medium to other carbon sources. The entire procedure typically takes ?4 d including bacteria transformation and image analysis. The majority of this protocol is applicable to sensing other metabolites and proteins in living bacteria. PMID:24356773

Strack, Rita L; Song, Wenjiao; Jaffrey, Samie R

2014-01-01

338

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

339

Simple office-based behavioral approach to patients with chronic belching.  

PubMed

Chronic belching can be a difficult and socially disabling symptom often attributed to reflux with poor response to therapy. In patients where aerophagia is identified as a clear cause, treatment with baclofen may not be tolerated, and biofeedback therapy is time-intensive and may still not be effective. In this pilot study, an office-based easy-to-perform method based on sustained glottal opening was used in five patients with chronic belching, in whom reflux and other causes had been excluded. Treatment consisted of having the patient breathe slowly and diaphragmatically with his or her mouth open during supine, then sitting periods to prevent belching. When this was successful, patients were then counseled on continuing this breathing with mouth slightly ajar as an outpatient using this persistently. Wide mouth opening was used for rescue therapy of belching attacks. All five patients responded to the office-based therapy with complete cessation of belching during the visit. At 1-month follow up, four patients remained asymptomatic. One patient was asymptomatic but for two breakthrough attacks easily managed with the protocol. A simple office-based procedure based on complete glottal opening can be curative for a subset of patients with chronic eructation secondary to repetitive air swallowing. PMID:23199281

Katzka, D A

2013-08-01

340

A Ratiometric Fluorescent Probe Based on ESIPT and AIE Processes for Alkaline Phosphatase Activity Assay and Visualization in Living Cells.  

PubMed

Alkaline phosphatase (ALP) activity is regarded as an important biomarker in medical diagnosis. A ratiometric fluorescent probe is developed based on a phosphorylated chalcone derivative for ALP activity assay and visualization in living cells. The probe is soluble in water and emits greenish-yellow in aqueous buffers. In the presence of ALP, the emission of probe changes to deep red gradually with ratiometric fluorescent response due to formation and aggregation of enzymatic product, whose fluorescence involves both excited-state intramolecular proton transfer and aggregation-induced emission processes. The linear ratiometric fluorescent response enables in vitro quantification of ALP activity in a range of 0-150 mU/mL with a detection limit of 0.15 mU/mL. The probe also shows excellent biocompatibility, which enables it to apply in ALP mapping in living cells. PMID:25208827

Song, Zhegang; Kwok, Ryan T K; Zhao, Engui; He, Zikai; Hong, Yuning; Lam, Jacky W Y; Liu, Bin; Tang, Ben Zhong

2014-10-01

341

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

342

Naphthalene, Phenanthrene, and Pyrene as DNA Base Analogues: Synthesis, Structure, and Fluorescence in DNA  

PubMed Central

We describe the synthesis, structures, and DNA incorporation of deoxyribonucleosides carrying polycyclic aromatic hydrocarbons as the DNA “base” analogue. The new polycyclic compounds are 1-naphthyl, 2-naphthyl, 9-phenanthrenyl, and 1-pyrenyl deoxynucleosides. The compounds are synthesized using a recently developed C-glycosidic bond formation method involving organocadmium derivatives of the aromatic compounds coupling with a 1?-chlorodeoxyribose precursor. The principal products of this coupling are the ?-anomers of the deoxyribosides. An efficient method has also been developed for epimerization of the ?-anomers to ?-anomers by acid-catalyzed equilibration; this isomerization is successfully carried out on the four polycyclic nucleosides as well as two substituted phenyl nucleosides. The geometry of the anomeric substitution is derived from 1H NOE experiments and is also correlated with a single-crystal X-ray structure of one ?-isomer. Three of the polycyclic C-nucleoside derivatives are incorporated into DNA oligonucleotides via their phosphoramidite derivatives; the pyrenyl and phenanthrenyl derivatives are shown to be fluorescent in a DNA sequence. The results (1) broaden the scope of our C-glycoside coupling reaction, (2) demonstrate that (using a new acid-catalyzed epimerization) both ?- and ?-anomers are easily synthesized, and (3) constitute a new class of deoxynucleoside derivatives. Such nucleoside analogues may be useful as biophysical probes for the study of noncovalent interactions such as aromatic ?-stacking in DNA. In addition, the fluorescence of the phenanthrene and pyrene nucleosides may make them especially useful as structural probes. PMID:20865136

Ren, Rex X.-F.; Chaudhuri, Narayan C.; Paris, Pamela L.; Rumney, Squire; Kool, Eric T.

2009-01-01

343

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

344

Development of an underwater multispectral fluorescence based oil spill sensor system for the marine environment  

SciTech Connect

This poster describes the development of an underwater optical fluorescence sensor system to detect the presence of petroleum hydrocarbon contaminants in the marine environment. The system is designed for long term continuous underwater operation and will be used primarily to provide real time notification of the occurrence of a petroleum leak or spill at marine facilities. The sensor utilizes broadband UV excitation from a pulsed xenon lamp to generate fluorescence emission in contaminated sea water. It can detect floating product (surface sheen) from below the surface as well as detect dissolved phase PAHs in the water column. Multispectral emission information is used to distinguish between several possible petroleum classes and also to eliminate false positive interference from non-petroleum based fluorophores such as chlorophyll, cleaning detergents, and sea dye. Real time qualitative identification yields an important advantage in terms of rapidly resolving questions of spill origin or in determining an appropriate response. The design uses the optical energy of the UV excitation source to prevent biofouling on the surface of the optical window thereby greatly extending the usable field lifetime of the {open_quotes}deploy and forget{close_quotes} instrument.

Andrews, J.M.; Lieberman, S.H. [Naval Command, San Diego, CA (United States)

1997-06-01

345

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

346

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

347

Optochemical sensor based on screenprinted fluorescent sensorspots surrounded by organic photodiodes for multianalyte detection  

NASA Astrophysics Data System (ADS)

A compact, integrated photoluminescence based oxygen sensor, utilizing an organic light emitting device (OLED) as the light source and an organic photodiode (OPD) as the detection unit, is described. The detection system of the sensor array consists of an array of circular screen-printed fluorescent sensor spots surrounded by organic photodiodes as integrated fluorescence detectors. The OPD originates from the well-known Tang photodiode, consisting of a stacked layer of copper phthalocyanine (CuPc, p-type material) and perylene tetracarboxylic bisbenzimidazole (PTCBi, n-type material). An additional layer of tris-8-hydroxyquinolinatoaluminium (Alq3, n-type material) was inserted between the PTCBi layer and cathode. An ORMOCERR layer was used as encapsulation layer. For excitation an organic light emitting diode is used. The sensor spot and the detector are processed on the same flexible substrate. This approach not only simplifies the detection system by minimizing the numbers of required optical components - no optical filters have to be used for separating the excitation light and the luminescent emission-, but also has a large potential for low-cost sensor applications. The feasibility of the concept is demonstrated by an integrated oxygen sensor, indicating good performance. Sensor schemes for other chemical parameters are proposed.

Kraker, E.; Lamprecht, B.; Haase, A.; Jakopic, G.; Abel, T.; Konrad, C.; Köstler, S.; Tscherner, M.; Stadlober, B.; Mayr, T.

2010-08-01

348

Characterization of Vibrio cholerae neuraminidase by a novel mechanism-based fluorescent labeling reagent.  

PubMed

Vibrio cholerae neuraminidase (VCNA) plays a significant role in the pathogenesis of cholera by removing sialic acid residues from higher-order gangliosides to an unmasked GM1, the essential receptor for cholera toxin. Here we report that a novel mechanism-based fluorescent labeling reagent, 5-acetamido-2-(4-N-5-dimethylaminonaphthalene-1-sulfonyl-2-difluoromethylphenyl)-3,5-dideoxy-d-glycero-alpha-d-galacto-2-nonulopyranosonic acid (1), becomes a unique irreversible inhibitor of VCNA. Characterization of an inactivated VCNA by MALDI-TOF/TOFMS analysis revealed that the Asp-576 and Arg-577 residues, which are located within the (576)DRFF(579) sequence, were specifically labeled with this suicide-type fluorescent substrate. Neither Asp-576 nor Arg-577 has ever been known to contribute to a specific residue in the rigid and highly conserved active site of VCNA investigated by crystallographic analysis, suggesting that a flexible beta-turn structure containing this sequence may have a crucial role in the dynamic nature of substrate recognition and catalytic action by VCNA. PMID:16128567

Hinou, Hiroshi; Kurogochi, Masaki; Shimizu, Hiroki; Nishimura, Shin-Ichiro

2005-09-01

349

Design, implementation, and field testing of a portable fluorescence-based vapor sensor.  

PubMed

The design and implementation of a portable fluorescence-based vapor sensing system are described. The system incorporates previously developed microsensor array technology into a compact, low-power device capable of collecting and delivering ambient vapor samples to the array while monitoring and recording the fluorescent responses of the sensors. The sensors respond differentially when exposed to a sample vapor and, when processed using a support vector machine (SVM) pattern recognition algorithm, are shown to discriminate between three classes of petroleum distillates. The system was characterized using sample vapors prepared under several different conditions in three sensing scenarios. The first scenario demonstrates the basic operational capability of the device in the field by presenting high concentration vapors to the array. The second scenario introduces the potential for a greater degree of variability in both sample vapor concentration and composition in an effort to emulate real-world sensing conditions. The third scenario uses an on-board trained pattern recognition algorithm to identify unknown vapors as their responses are collected. The device demonstrated high classification accuracy throughout the field tests and is capable of improving its classification accuracy when challenged with samples presented under variable ambient conditions by enhancing the signal-to-noise ratio of the array response. PMID:19563211

Aernecke, Matthew J; Guo, Jian; Sonkusale, Sameer; Walt, David R

2009-07-01

350

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

351

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

352

Group-selective antibodies based fluorescence immunoassay for monitoring opiate drugs.  

PubMed

A novel carboxylic acid derivative of monoacetylmorphine (MAM-COOH) was synthesized and conjugated with bovine serum albumin (BSA) for generating polyclonal antibodies against the target molecule heroin and its major metabolites. The conjugate was characterized by fluorescence spectroscopy, polyacrylamide gel electrophoresis, and mass spectrometry to confirm the extent of haptenization of the carrier protein. A high titer (1:64,0000) of antibody was obtained by using the conjugate with an optimum protein/hapten molar ratio of 1:100. The generated antibody showed good binding affinity with heroin and its metabolites monoacetylmorphine (MAM) and morphine. The relative affinity constant (K (aff)) of the antibody was 3.1 x 10(7) l mol(-1), and the IC(50) values obtained for heroin, MAM, morphine, and codeine were 0.01, 0.013, 0.012, and 0.014 ng ml(-1), respectively. A fluorescence-based competitive inhibition immunoassay procedure was developed for the estimation of heroin and its major metabolites in standard and biofludic samples over a concentration range up to 0.01 ng ml(-1) with good signal reproducibility (p < 0.05). The method can be used as a convenient quantitative tool for the sensitive screening of major metabolites of heroin in biological samples. PMID:18663434

Gandhi, Sonu; Sharma, Prince; Capalash, Neena; Verma, R S; Suri, C Raman

2008-09-01

353

Simple Sodium Dodecyl Sulfate-Assisted Sample Preparation Method for LC-MS-based Proteomic Applications  

SciTech Connect

Sodium dodecyl sulfate (SDS) is one of the most popular laboratory reagents used for highly efficient biological sample extraction; however, SDS presents a significant challenge to LC-MS-based proteomic analyses due to its severe interference with reversed-phase LC separations and electrospray ionization interfaces. This study reports a simple SDS-assisted proteomic sample preparation method facilitated by a novel peptide-level SDS removal protocol. After SDS-assisted protein extraction and digestion, SDS was effectively (>99.9%) removed from peptides through ion substitution-mediated DS- precipitation with potassium chloride (KCl) followed by {approx}10 min centrifugation. Excellent peptide recovery (>95%) was observed for less than 20 {mu}g of peptides. Further experiments demonstrated the compatibility of this protocol with LC-MS/MS analyses. The resulting proteome coverage from this SDS-assisted protocol was comparable to or better than those obtained from other standard proteomic preparation methods in both mammalian tissues and bacterial samples. These results suggest that this SDS-assisted protocol is a practical, simple, and broadly applicable proteomic sample processing method, which can be particularly useful when dealing with samples difficult to solubilize by other methods.

Zhou, Jianying; Dann, Geoffrey P.; Shi, Tujin; Wang, Lu; Gao, Xiaoli; Su, Dian; Nicora, Carrie D.; Shukla, Anil K.; Moore, Ronald J.; Liu, Tao; Camp, David G.; Smith, Richard D.; Qian, Weijun

2012-03-10

354

Scenario based outdoor simulation in pre-hospital trauma care using a simple mannequin model  

PubMed Central

Introduction We describe a system of scenario-based training using simple mannequins under realistic circumstances for the training of pre-hospital care providers. Methods A simple intubatable mannequin or student volunteers are used together with a training version of the equipment used on a routine basis by the pre-hospital care team (doctor + paramedic). Training is conducted outdoors at the base location all year round. The scenarios are led by scenario facilitators who are predominantly senior physicians. Their role is to brief the training team and guide the scenario, results of patient assessment and the simulated responses to interventions and treatment. Pilots, fire-fighters and medical students are utilised in scenarios to enhance realism by taking up roles as bystanders, additional ambulance staff and police. These scenario participants are briefed and introduced to the scene in a realistic manner. After completion of the scenario, the training team would usually be invited to prepare and deliver a hospital handover as they would in a real mission. A formal structured debrief then takes place. Results This training method technique has been used for the training of all London Helicopter Emergency Medical Service (London HEMS) doctors and paramedics over the last 24 months. Informal participant feedback suggests that this is a very useful teaching method, both for improving motor skills, critical decision-making, scene management and team interaction. Although formal assessment of this technique has not yet taken place we describe how this type of training is conducted in a busy operational pre-hospital trauma service. Discussion The teaching and maintenance of pre-hospital care skills is essential to an effective pre-hospital trauma care system. Simple mannequin based scenario training is feasible on a day-to-day basis and has the advantages of low cost, rapid set up and turn around. The scope of scenarios is limited only by the imagination of the trainers. Significant effort is made to put the participants into "the Zone" - the psychological mindset, where they believe they are in a realistic setting and treating a real patient, so that they gain the most from each teaching session. The method can be used for learning new skills, communication and leadership as well as maintaining existing skills. Conclusion The method described is a low technology, low cost alternative to high technology simulation which may provide a useful adjunct to delivering effective training when properly prepared and delivered. We find this useful for both induction and regular training of pre-hospital trauma care providers. PMID:20230636

2010-01-01

355

A simple transformer-based resonator architecture for low phase noise LC oscillators  

E-print Network

This thesis investigates the use of a simple transformer-coupled resonator to increase the loaded Q of a LC resonant tank. The windings of the integrated transformer replace the simple inductors as the inductive elements ...

Ogunnika, Olumuyiwa Temitope, 1978-

2004-01-01

356

Comparative study on compact planar waveguide based photonic integrated couplers using simple effective index method  

NASA Astrophysics Data System (ADS)

The miniaturization of photonic components in integrated optic waveguide devices to microscale platform has attracted enormous attention from the researchers and entrepreneurs. In this paper, we present and report a comparative study of photonic integrated planar waveguide based couplers using a mathematical model based on sinusoidal mode simple effective index method (SEIM). The basic photonic integrated components such as directional coupler (DC), two mode interference (TMI) coupler and multimode interference (MMI) coupler have been designed and fabricated using the versatile SiON waveguide technology (SiON as the waveguide core material using silica waveguide). The experimental results have been compared with the SEIM based theoretical results and further verified with the commercially available software tool based on beam propagation method (BPM). With a focus towards device compactness, particular emphasis is placed on device geometry in an endeavour to achieve the same. In this direction, the theoretical and experimental results obtained have been compared with tooth shaped grating assisted geometry for these photonic components. It is found that the grating assisted structures have the beat length ~0.5 times lower than that of the conventional geometry. Further it is seen that the beat length of TMI coupler is smaller compared to the DC and MMI coupler.

Deka, Bidyut; Dutta, Aradhana; Sahu, Partha P.

2013-11-01

357

Progress In Electromagnetics Research, Vol. 140, 297311, 2013 SIMPLE, TAYLOR-BASED WORST-CASE MODEL FOR  

E-print Network

Rennes Cedex 7, France Abstract--To obtain Electromagnetic Compatibility (EMC), we would like to study Transverse Electromagnetic (GTEM) cell. 1. INTRODUCTION Pursuing Electromagnetic Compatibility (EMCProgress In Electromagnetics Research, Vol. 140, 297­311, 2013 SIMPLE, TAYLOR-BASED WORST

Boyer, Edmond

358

EVALUATION OF SHEAR RESISTANCE OF PERFOBOND STRIP BASED ON SIMPLE PUSH-OUT TEST  

NASA Astrophysics Data System (ADS)

A perfobond strip is generally used as the shear connector in the various steel-concrete hybrid structures and a few design formulas for evaluating the shear resistance of the perfobond strip are proposed. However, these design formulas are not always applicable to the one employed in the steel-concrete rigid frame bridge, since the formulas are established based on the standard push-out specimen for the stud shear connector in which some cracks may occur in the concrete block of the specimen during the test. In this paper, the shear resistance of the perfobond strip are examined experimentally by employing the simple push-out specimen different from the standard one for the stud shear connector. As a result, the design formula is proposed for evaluating the shear resistance of the perfobond strip taking into account the proportion of the concrete block as well as the perforation size and the concrete compressive strength.

Nakajima, Akinori; Koseki, Soichiro; Hashimoto, Masatoshi; Suzuki, Yasuo; Nguyen, Minh Hai

359

A Simple Isolation Criterion based on 3D Redshift Space Mapping  

E-print Network

We selected a sample of galaxies, extremely isolated in 3D redshift space, based on data from NED and the ongoing ALFALFA HI (21cm) survey. A simple selection criterion was employed: having no neighbors closer than 300 km/s in 3D redshift space. The environments of galaxies, selected using this criterion and NED data alone, were analyzed theoretically using a constrained simulation of the local Universe, and were found to be an order of magnitude less dense than environments around randomly selected galaxies. One third of the galaxies selected using NED data alone did not pass the criterion when tested with ALFALFA data, implying that the use of unbiased HI data significantly improves the quality of the sample.

Spector, Oded

2009-01-01

360

A Simple Technique Based on a Single Optical Trap for the Determination of Bacterial Swimming Pattern  

PubMed Central

Bacterial motility is associated to a wide range of biological processes and it plays a key role in the virulence of many pathogens. Here we describe a method to distinguish the dynamic properties of bacteria by analyzing the statistical functions derived from the trajectories of a bacterium trapped by a single optical beam. The approach is based on the model of the rotation of a solid optically trapped sphere. The technique is easily implemented in a biological laboratory, since with only a small number of optical and electronic components a simple biological microscope can be converted into the required analyzer. To illustrate the functionality of this method, we probed several serovar Typhimurium mutants that differed from the wild-type with respect to their swimming patterns. In a further application, the motility dynamics of the Typhimurium mutant were characterized. PMID:23637869

Martínez, Ignacio A.; Campoy, Susana; Tort, Meritxell; Llagostera, Montserrat; Petrov, Dmitri

2013-01-01

361

Highly flexible titanium dioxide-based resistive switching memory with simple fabrication  

NASA Astrophysics Data System (ADS)

We demonstrate a flexible resistive switching random access memory (ReRAM), which is a promising next-generation memory on a flexible substrate. The proposed method enables us to fabricate an Al/TiO2/Al structure on a polyimide substrate, which has highly flexible and durable characteristics, rather than a Si-based substrate by a simple fabrication process. To understand the role of oxygen vacancies in TiO2, our devices was analyzed by X-ray photoelectron spectroscopy (XPS) and XPS depth profile analyses. Moreover, severe bending of the device did not affect the memory performance owing to its small channel length and the high ductility of the electrode. The results presented here can provide a new approach to the fabrication of nonvolatile memories for flexible electronic devices.

Yeom, Seung-Won; Park, Suk Won; Jung, In-sung; Kim, Minseok; Ha, Hyeon Jun; Shim, Joon Hyung; Ju, Byeong-kwon

2014-10-01

362

Synthesis of antimony-based nanowires using the simple vapor deposition method.  

PubMed

III-V nanowires have attracted plenty of attention because of their potential outstanding performance in a wide range of applications. However, compared to other III-V nanowires, the synthesis of high quality Sb-based nanowires is less developed, which obstructs the progress towards further applications. In this study we report high quality GaSb and InSb nanowires synthesized by a simple vapor deposition method. Epitaxial growth of nanowires on growth substrates is demonstrated. Te doped GaSb nanowires are achieved through in situ doping during the vapor deposition process. Electrical measurements of nanowire field-effect transistors show high performance of the synthesized InSb nanowires. PMID:22438329

Zi, Yunlong; Zhao, Yanjie; Candebat, Drew; Appenzeller, Joerg; Yang, Chen

2012-07-16

363

A simple scanning spectrometer based on a stretchable elastomeric reflective grating  

NASA Astrophysics Data System (ADS)

We report a scanning optical spectrometer based on the use of a stretchable elastomeric reflective grating. The grating is obtained by supersonic cluster beam implantation of silver nanoparticles on polydimethylsiloxane previously grooved by molding to create a replica of a commercial digital versatile disk grating. The use of a stretchable grating allows the spectrometer spanning the whole optical wavelength range by solely extending the diffraction element by more than 100% of its original dimensions. The stretchable reflective optical grating shows excellent performances and stability upon thousands of stretching cycles. The use of this elastomeric element makes the optical layout and the mechanics of the spectrometer extremely simple and advantageous for those applications where spectral resolution is not a major requirement. As a proof of principle, we present the absorption spectrum of Rhodamine B in solution obtained by our spectrometer and compared to commercial instruments.

Ghisleri, C.; Potenza, M. A. C.; Ravagnan, L.; Bellacicca, A.; Milani, P.

2014-02-01

364

Intrinsic Ge nanowire nonvolatile memory based on a simple core-shell structure  

NASA Astrophysics Data System (ADS)

Intrinsic Ge nanowires (NWs) with a Ge core covered by a thick Ge oxide shell are utilized to achieve nanoscale field-effect transistor nonvolatile memories, which show a large memory window and a high ON/OFF ratio with good retention. The retainable surface charge trapping is considered to be responsible for the memory effect, and the Ge oxide shell plays a key role as the insulating tunneling dielectric which must be thick enough to prevent stored surface charges from leaking out. Annealing the device in air is demonstrated to be a simple and effective way to attain thick Ge oxide on the Ge NW surface, and the Ge-NW-based memory corresponding to thick Ge oxide exhibits a much better retention capability compared with the case of thin Ge oxide.

Chen, Wen-Hua; Liu, Chang-Hai; Li, Qin-Liang; Sun, Qi-Jun; Liu, Jie; Gao, Xu; Sun, Xuhui; Wang, Sui-Dong

2014-02-01

365

Simple sequence repeat-based association analysis of fruit traits in eggplant (Solanum melongena).  

PubMed

Association mapping based on linkage disequilibrium (LD) provides a promising tool to identify quantitative trait loci (QTLs) in plant resources. A total of 141 eggplant (Solanum melongena L.) accessions were selected to detect simple sequence repeat (SSR) markers associated with nine fruit traits. Population structure analysis was performed with 105 SSR markers, which revealed that two subgroups were present in this population. LD analysis exhibited an extensive long-range LD of approximately 11 cM. A total of 49 marker associations related to eight phenotypic traits were identified to involve 24 different markers, although no association was found with the trait of fruit glossiness. To our knowledge, this is the 1st approach to use a genome-wide association study in eggplant with SSR markers. These results suggest that the association analysis approach could be a useful alternative to traditional linkage mapping to detect putative QTLs in eggplant. PMID:24301934

Ge, H Y; Liu, Y; Zhang, J; Han, H Q; Li, H Z; Shao, W T; Chen, H Y

2013-01-01

366

A simple technique based on a single optical trap for the determination of bacterial swimming pattern.  

PubMed

Bacterial motility is associated to a wide range of biological processes and it plays a key role in the virulence of many pathogens. Here we describe a method to distinguish the dynamic properties of bacteria by analyzing the statistical functions derived from the trajectories of a bacterium trapped by a single optical beam. The approach is based on the model of the rotation of a solid optically trapped sphere. The technique is easily implemented in a biological laboratory, since with only a small number of optical and electronic components a simple biological microscope can be converted into the required analyzer. To illustrate the functionality of this method, we probed several Salmonella enterica serovar Typhimurium mutants that differed from the wild-type with respect to their swimming patterns. In a further application, the motility dynamics of the S. Typhimurium cheV mutant were characterized. PMID:23637869

Martínez, Ignacio A; Campoy, Susana; Tort, Meritxell; Llagostera, Montserrat; Petrov, Dmitri

2013-01-01

367

A simple enthalpy-based lattice Boltzmann scheme for complicated thermal systems  

NASA Astrophysics Data System (ADS)

To extend the lattice Boltzmann (LB) method to describe the applicable energy systems, the first key step is to build a suitable thermal LB model and corresponding boundary treatments. There are two main shortcomings in the existing related works: either some additional energy source terms are inconvenient to be naturally incorporated or the implementation of non-Dirichlet-type thermal boundary conditions is extremely difficult and sometimes impossible in them for complicated thermal systems, which restrict their applicability to only a few special classes of problems. In order to overcome these drawbacks by a simple way, in this paper a thermal LB model and corresponding boundary treatments are constructed based on the total enthalpy. The specific benefits due to the introduction of the total enthalpy are analyzed and it is found that the numerical results obtained by the present scheme agree well with the analytical solutions and/or the data reported in previous studies.

Chen, Sheng; Luo, K. H.; Zheng, Chuguang

2012-10-01

368

Epitaxial Growth of GaN-based LEDs on Simple Sacrificial Substrates  

SciTech Connect

The objective of this project is to produce alternative substrate technologies for GaN-based LEDs by developing an ALD interlayer of Al{sub 2}O{sub 3} on sacrificial substrates such as ZnO and Si. A sacrificial substrate is used for device growth that can easily be removed using a wet chemical etchant leaving only the thin GaN epi-layer. After substrate removal, the GaN LED chip can then be mounted in several different ways to a metal heat sink/reflector and light extraction techniques can then be applied to the chip and compared for performance. Success in this work will lead to high efficiency LED devices with a simple low cost fabrication method and high product yield as stated by DOE goals for its solid state lighting portfolio.

Ian Ferguson; Chris Summers

2009-12-31

369

Micelle-induced versatile sensing behavior of bispyrene-based fluorescent molecular sensor for picric acid and PYX explosives.  

PubMed

The effect of surfactant micelles on the photophysical properties of a cationic bispyrene fluorophore, Py-diIM-Py, was systemically examined. The results from series of measurements including UV-vis absorption, steady-state fluorescence emission, quantum yield, fluorescence lifetime, and time-resolved emission spectra reveal that the cationic fluorophore is only encapsulated by the anionic sodium dodecyl sulfate (SDS) surfactant micelles and not incorporated in the cationic dodecyltrimethylammonium bromide (DTAB) and neutral Triton X-100 (TX100) surfactant micelles. This different fluorophore location in the micellar solutions significantly influences its sensing behavior to various explosives. Fluorescence quenching studies reveal that the simple variation of micellar systems leads to significant changes in the sensitivity and selectivity of the fluorescent sensor to explosives. The sensor exhibits an on-off response to multiple explosives with the highest sensitivity to picric acid (PA) in the anionic SDS micelles. In the cationic DTAB micelles, it displays the highest on-off responses to PYX. Both the sensitivity and selectivity to PYX in the cationic micelles are enhanced compared with that to PA in the anionic micelles. However, the poor encapsulation in the neutral surfactant TX100 micelles leads to fluorescence instability of the fluorophore and fails to function as a sensor system. Time-resolved fluorescence decays in the presence of explosives reveal that the quenching mechanism of two micellar sensor systems to explosives is static in nature. The present work demonstrates that the electrostatic interaction between the cationic fluorophore and differently charged micelles plays a determinative role in adjusting its distribution in micellar solutions, which further influences the sensing behavior of the obtained micellar sensor systems. PMID:24922083

Ding, Liping; Bai, Yumei; Cao, Yuan; Ren, Guijia; Blanchard, Gary J; Fang, Yu

2014-07-01

370

Rapid and Quantitative Detection of Zoonotic Influenza A Virus Infection Utilizing Coumarin-derived dendrimer-based Fluorescent Immunochromatographic Strip Test (FICT)  

PubMed Central

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

371

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

372

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

373

Simple Machines Made Simple.  

ERIC Educational Resources Information Center

Simple machines have become a lost point of study in elementary schools as teachers continue to have more material to cover. This manual provides hands-on, cooperative learning activities for grades three through eight concerning the six simple machines: wheel and axle, inclined plane, screw, pulley, wedge, and lever. Most activities can be…

St. Andre, Ralph E.

374

Cell-based and in vivo spectral analysis of fluorescent proteins for multiphoton microscopy  

NASA Astrophysics Data System (ADS)

Multiphoton microscopy of cells and subcellular structures labeled with fluorescent proteins is the state-of-the-art technology for longitudinal imaging studies in tissues and living animals. Successful analysis of separate cell populations or signaling events by intravital microscopy requires optimal pairing of multiphoton excitation wavelengths with spectrally distinct fluorescent proteins. While prior studies have analyzed two photon absorption properties of isolated fluorescent proteins, there is limited information about two photon excitation and fluorescence emission profiles of fluorescent proteins expressed in living cells and intact tissues. Multiphoton microscopy was used to analyze fluorescence outputs of multiple blue, green, and red fluorescent proteins in cultured cells and orthotopic tumor xenografts of human breast cancer cells. It is shown that commonly used orange and red fluorescent proteins are excited efficiently by 750 to 760 nm laser light in living cells, enabling dual color imaging studies with blue or cyan proteins without changing excitation wavelength. It is also shown that small incremental changes in excitation wavelength significantly affect emission intensities from fluorescent proteins, which can be used to optimize multi-color imaging using a single laser wavelength. These data will direct optimal selection of fluorescent proteins for multispectral two photon microscopy.

Salomonnson, Emma; Mihalko, Laura Anne; Verkhusha, Vladislav V.; Luker, Kathryn E.; Luker, Gary D.

2012-09-01

375

Single-fluorophore-based fluorescent probes enable dual-channel detection of Ag? and Hg²? with high selectivity and sensitivity.  

PubMed

A new type of fluorescent probe capable of detecting Ag(+) and Hg(2+) in two independent channels was developed in the present work. Specifically, in CH3CN-MOPS mixed solvents with CH3CN/MOPS ratio (v/v) of 15/85, this type of probe fluoresced weakly, and the addition of Ag(+) remarkably induced fluorescence enhancement of the probe. In CH3CN-MOPS mixed solvents with the percentage of CH3CN increased up to 65%, the probe was highly fluorescent and addition of Hg(2+) dramatically induced the fluorescence quenching. Thus, using such single-fluorophore-based probe and tuning the polarity of the mixed solvent, Ag(+), and Hg(2+) can be detected in independent channels with high selectivity and sensitivity. As a result, the mutual interference usually encountered in most cases of Ag(+) and Hg(2+) sensing owing to the similar fluorescence response that these two ions induced, can be effectively circumvented by using the probes developed herein. PMID:25066721

Lv, Yanlin; Zhu, Lili; Liu, Heng; Wu, Yishi; Chen, Zili; Fu, Hongbing; Tian, Zhiyuan

2014-08-11

376

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

377

Electrochemical immobilization of Fluorescent labelled probe molecules on a FTO surface for affinity detection based on photo-excited current  

NASA Astrophysics Data System (ADS)

Photo-excited current can be generated at a molecular interface between a photo-excited molecules and a semi-conductive material in appropriate condition. The system has been recognized for promoting photo-energy devices such as an organic dye sensitized solar-cell. The photo-current generated reactions are totally dependent on the interfacial energy reactions, which are in a highly fluctuated interfacial environment. The authors investigated the photo-excited current reaction to develop a smart affinity detection method. However, in order to perform both an affinity reaction and a photo-excited current reaction at a molecular interface, ordered fabrications of the functional (affinity, photo-excitation, etc.) molecules layer on a semi-conductive surface is required. In the present research, we would like to present the fabrication and functional performance of photo-excited current-based affinity assay device and its application for detection of endocrine disrupting chemicals. On the FTO surface, fluorescent pigment labelled affinity peptide was immobilized through the EC tag (electrochemical-tag) method. The modified FTO produced a current when it was irradiated with diode laser light. However, the photo current decreased drastically when estrogen (ES) coexisted in the reaction solution. In this case, immobilized affinity probe molecules formed a complex with ES and estrogen receptor (ER). The result strongly suggests that the photo-excited current transduction between probe molecule-labelled cyanine pigment and the FTO surface was partly inhibited by a complex that formed at the affinity oligo-peptide region in a probe molecule on the FTO electrode. The bound bulky complex may act as an impediment to perform smooth transduction of photo-excited current in the molecular interface. The present system is new type of photo-reaction-based analysis. This system can be used to perform simple high-sensitive homogeneous assays.

Haruyama, Tetsuya; Wakabayashi, Ryo; Cho, Takeshi; Matsuyama, Sho-taro

2011-10-01

378

Flow-through optosensing device implemented with photochemically-induced fluorescence for the rapid and simple screening of metsulfuron methyl in environmental waters.  

PubMed

This paper describes the implementation of a flow-injection solid phase spectroscopy (FI-SPS) system with photochemically induced fluorescence (PIF) in micellar medium for the determination of metsulfuron-methyl (MET). The micelles containing a strongly fluorescent photoproduct generated after UV irradiation of the herbicide are strongly retained on C(18) silica gel filling the flow-cell placed in the detection area and the photoproduct is monitored at 323 and 378 nm for excitation and emission wavelengths, respectively. The solid support is easily regenerated for subsequent sample injections (at least up to 500 cycles tested). The system was calibrated for two injection volumes, 300 and 1000 microl. The detection limits and relative standard deviations were 0.71 and 0.14 ng ml(-1), and 4.5 and 3.3% for each injection volume, respectively. The system shows a very high throughput, 34 (300 microl) and 36 (1000 microl) analysis per hour. The optosensor was successfully applied to the herbicide determination in river, well and irrigation waters (recovery ranges from 96.0 to 106.0%). PMID:19436868

López Flores, Javier; Fernández de Córdova, María L; Molina Díaz, Antonio

2009-05-01

379

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

380

High efficiency fluorescent excimer lamps: An alternative to mercury based UVC lamps  

SciTech Connect

A high efficiency xenon excimer lamp radiating at 172 nm, with an internal phosphor coating shifting to UVC has been demonstrated, showing the feasibility of a cost effective alternative to UVC mercury lamps. Fluorescent lamps so designed can be fabricated in various geometries with high efficiency. Unlike other xenon excimer lamps based on dielectric barrier discharges this new system is highly compatible with existing and proposed phosphors as it operates in an inert gas environment at modest temperature and is subject only to 172 nm primary radiation. Using a lamp coated with a UVC phosphor we have demonstrated the feasibility of germicidal and curing lamps with 40% energy conversion efficiency and high power density. These lamps are rapidly switchable, have long projected lifetimes and are compatible with dimmers.

Masoud, N. M. [UV Solutions Inc, Newark, New Jersey 07103 (United States) [UV Solutions Inc, Newark, New Jersey 07103 (United States); Physics and Chemistry Department, Milwaukee School of Engineering, Milwaukee, Wisconsin 53202 (United States); Murnick, D. E. [UV Solutions Inc, Newark, New Jersey 07103 (United States) [UV Solutions Inc, Newark, New Jersey 07103 (United States); Department of Physics, Rutgers University, Newark, New Jersey 07102 (United States)

2013-12-15

381

High efficiency fluorescent excimer lamps: an alternative to mercury based UVC lamps.  

PubMed

A high efficiency xenon excimer lamp radiating at 172 nm, with an internal phosphor coating shifting to UVC has been demonstrated, showing the feasibility of a cost effective alternative to UVC mercury lamps. Fluorescent lamps so designed can be fabricated in various geometries with high efficiency. Unlike other xenon excimer lamps based on dielectric barrier discharges this new system is highly compatible with existing and proposed phosphors as it operates in an inert gas environment at modest temperature and is subject only to 172 nm primary radiation. Using a lamp coated with a UVC phosphor we have demonstrated the feasibility of germicidal and curing lamps with 40% energy conversion efficiency and high power density. These lamps are rapidly switchable, have long projected lifetimes and are compatible with dimmers. PMID:24387421

Masoud, N M; Murnick, D E

2013-12-01

382

High efficiency fluorescent excimer lamps: An alternative to mercury based UVC lamps  

NASA Astrophysics Data System (ADS)

A high efficiency xenon excimer lamp radiating at 172 nm, with an internal phosphor coating shifting to UVC has been demonstrated, showing the feasibility of a cost effective alternative to UVC mercury lamps. Fluorescent lamps so designed can be fabricated in various geometries with high efficiency. Unlike other xenon excimer lamps based on dielectric barrier discharges this new system is highly compatible with existing and proposed phosphors as it operates in an inert gas environment at modest temperature and is subject only to 172 nm primary radiation. Using a lamp coated with a UVC phosphor we have demonstrated the feasibility of germicidal and curing lamps with 40% energy conversion efficiency and high power density. These lamps are rapidly switchable, have long projected lifetimes and are compatible with dimmers.

Masoud, N. M.; Murnick, D. E.

2013-12-01

383

Sensitive fluorescence detection of nucleic acids based on isothermal circular strand-displacement polymerization reaction.  

PubMed

Here we have developed a sensitive DNA amplified detection method based on isothermal strand-displacement polymerization reaction. This method takes advantage of both the hybridization property of DNA and the strand-displacement property of polymerase. Importantly, we demonstrate that our method produces a circular polymerization reaction activated by the target, which essentially allows it to self-detect. Functionally, this DNA system consists of a hairpin fluorescence probe, a short primer and polymerase. Upon recognition and hybridization with the target ssDNA, the stem of the hairpin probe is opened, after which the opened probe anneals with the primer and triggers the polymerization reaction. During this process of the polymerization reaction, a complementary DNA is synthesized and the hybridized target is displaced. Finally, the displaced target recognizes and hybridizes with another probe, triggering the next round of polymerization reaction, reaching a target detection limit of 6.4 x 10(-15) M. PMID:19129227

Guo, Qiuping; Yang, Xiaohai; Wang, Kemin; Tan, Weihong; Li, Wei; Tang, Hongxing; Li, Huimin

2009-02-01

384

A deep-blue OLED-based biochip for protein microarray fluorescence detection.  

PubMed

Integrated biochips exploit a multi-disciplinary approach to produce portable point-of-care medical diagnostic systems that uncouple diagnosis from centralized laboratories. These portable devices are cost effective and have several advantages including broader accessibility to health care worldwide. Fluorescence detection of a disease-specific probe excited by an optical source is one of the most diffused methods for quantitative analysis on biochips. Here we designed and characterized a miniaturized biochip based on a novel deep-blue organic light-emitting diode. The molecular design of the diode was optimized to excite a fluorophore-conjugated antibody and tested on a protein microarray configuration with good sensitivity and specificity. These findings will be instrumental for the development of next generation point-of-care biochips. PMID:23500475

Marcello, Alessandro; Sblattero, Daniele; Cioarec, Cristina; Maiuri, Paolo; Melpignano, Patrizia

2013-08-15

385

Impact of DNA sequence and oligonucleotide length on a polythiophene-based fluorescent DNA biosensor.  

PubMed

DNA hybridization is a universal and specific mechanism for the recognition of biological targets. Some cationic polythiophene transducers sensitive to DNA structure have been previously utilized to detect such biomolecules. Further characterization of these systems indicates that both DNA sequence composition and length modulate the biosensor performance. It appears that different repeated sequence patterns cause different conformational changes of the polythiophene, from a more relaxed form to an extremely rigid one. A length difference between the DNA oligonucleotide probe and target has a detrimental effect on the fluorescent signal, but it can be attenuated by changing the sequence composition of the protruding target sequence. This demonstrates that the nature of DNA can be critical for hybridization-based detection systems. PMID:23512409

Charlebois, Isabelle; Gravel, Catherine; Arrad, Naoual; Boissinot, Maurice; Bergeron, Michel G; Leclerc, Mario

2013-06-01

386

Sulfite determination by a biosensor based on bay leaf tissue homogenate: very simple and economical method.  

PubMed

Of all the food additives for which the FDA has received adverse reaction reports, the ones that most closely resemble true allergens are sulfur-based preservatives. Sulfites are used primarily as antioxidants to prevent or reduce discoloration of light-colored fruits and vegetables, such as dried apples and potatoes, and to inhibit the growth of microorganisms in fermented foods such as wine. This work aims to prepare an electrochemical biosensor based on bay leaf tissue homogenate that contains polyphenol oxidase enzyme abundantly for sulfite detection in foods. The principle of the biosensor is based on the inhibition effect of sulfites on polyphenol oxidase in the bioactive layer. Optimum conditions for the biosensor, such as temperature and pH, were investigated. Some stability parameters of the biosensor were also identified. The biosensor showed a linear calibration graph in the range of 25-100 microM sulfite. The biosensor presents a very simple, economical, reliable, and feasible method for sulfite detection in foods. PMID:19418312

Teke, Mustafa; Sezgintürk, Mustafa Kemal; Dinçkaya, Erhan

2009-01-01

387

On-bead fluorescent DNA nanoprobes to analyze base excision repair activities.  

PubMed

DNA integrity is constantly threatened by endogenous and exogenous agents that can modify its physical and chemical structure. Changes in DNA sequence can cause mutations sparked by some genetic diseases or cancers. Organisms have developed efficient defense mechanisms able to specifically repair each kind of lesion (alkylation, oxidation, single or double strand break, mismatch, etc). Here we report the adjustment of an original assay to detect enzymes' activity of base excision repair (BER), that supports a set of lesions including abasic sites, alkylation, oxidation or deamination products of bases. The biosensor is characterized by a set of fluorescent hairpin-shaped nucleic acid probes supported on magnetic beads, each containing a selective lesion targeting a specific BER enzyme. We have studied the DNA glycosylase alkyl-adenine glycosylase (AAG) and the human AP-endonuclease (APE1) by incorporating within the DNA probe a hypoxanthine lesion or an abasic site analog (tetrahydrofuran), respectively. Enzymatic repair activity induces the formation of a nick in the damaged strand, leading to probe's break, that is detected in the supernatant by fluorescence. The functional assay allows the measurement of DNA repair activities from purified enzymes or in cell-free extracts in a fast, specific, quantitative and sensitive way, using only 1 pmol of probe for a test. We recorded a detection limit of 1 ?g mL(-1) and 50 ?g mL(-1) of HeLa nuclear extracts for APE1 and AAG enzymes, respectively. Finally, the on-bead assay should be useful to screen inhibitors of DNA repair activities. PMID:24491778

Gines, Guillaume; Saint-Pierre, Christine; Gasparutto, Didier

2014-02-17

388

A low cytotoxic and ratiometric fluorescent nanosensor based on carbon-dots for intracellular pH sensing and mapping.  

PubMed

Intracellular pH plays a critical role in the function of cells, and its regulation is essential for most cellular processes. In this study, we demonstrate a fluorescence resonance energy transfer (FRET)-based ratiometric pH nanosensor with carbon-dot (CD) as the carrier. The sensor was prepared by covalently linking a pH-sensitive fluorescent dye (fluorescein isothiocyanate, FITC) onto carbon-dot. As the FRET donor, the carbon-dot exhibits bright fluorescence emission as well as ?ex-dependent photoluminescence emission, and a suitable excitation wavelength for the donor (CD) can be chosen to match the energy acceptor (fluorescein moiety). The fluorescein moieties on a CD undergo structural and spectral conversion as the pH changes, affording the nanoplatform a FRET-based pH sensor. The CD-based system exhibits a significant change in fluorescence intensity ratio between pH 4 and 8 with a pKa value of 5.69. It also displays excellent water dispersibility, good spectral reversibility, satisfactory cell permeability and low cytotoxicity. Following the living cell uptake, this nanoplatform with dual-chromatic emissions can facilitate real-time visualization of the pH evolution involved in the endocytic pathway of the nanosensor. This reversible and low cytotoxic fluorescent nanoplatform may be highly valuable in a variety of biological studies, such as endocytic trafficking, endosome/lysosome maturation, and pH regulation in subcellular organelles. PMID:23942146

Du, Fangkai; Ming, Yunhao; Zeng, Fang; Yu, Changmin; Wu, Shuizhu

2013-09-13

389

Determination of benzimidazolic fungicides in fruits and vegetables by supramolecular solvent-based microextraction/liquid chromatography/fluorescence detection.  

PubMed

A supramolecular solvent consisting of vesicles, made up of equimolecular amounts of decanoic acid (DeA) and tetrabutylammonium decanoate (Bu4NDe), dispersed in a continuous aqueous phase, is proposed for the extraction of benzimidazolic fungicides (BFs) from fruits and vegetables. Carbendazim (CB), thiabendazole (TB) and fuberidazole (FB) were extracted in a single step and no clean-up or concentration of extracts was needed. The high extraction efficiency obtained for BFs was a result of the different types of interactions provided by the supramolecular solvent (e.g. hydrophobic and hydrogen bonds) and the high number of solubilisation sites it contains. Besides simple and efficient, the proposed extraction approach was rapid, low-cost, environment friendly and it was implemented using conventional lab equipments. The target analytes were determined in the supramolecular extract by LC/fluorescence detection. They were separated in a Kromasil C18 (5 microm, 150 mm x 4.6 mm) column using isocratic elution [mobile phase: 60:40 (v/v) 50 mM phosphate buffer (pH 4)/methanol] and quantified at 286/320 nm (CB) and 300/350 nm (TB and FB) excitation/emission wavelengths, respectively. Quantitation limits provided by the supramolecular solvent-based microextraction (SUSME)/LC/fluorescence detection proposed method for the determination of CB, TB and FB in fruits and vegetables were 14.0, 1.3 and 0.03 microg kg(-1), respectively, values far below the current maximum residue levels (MRLs) established by the European Union, i.e. 100-2000 microg kg(-1) for CB, 50-5000 microg kg(-1) for TB and 50 microg kg(-1) for FB. The precision of the method, expressed as relative standard deviation, for inter-day measurements (n=13) was 3.3% for CB (50 microg kg(-1)), 3.5% for TB (10 microg kg(-1)) and 2.8% for FB (0.5 microg kg(-1)) and recoveries for fruits (oranges, tangerines, lemons, limes, grapefruits, apples, pears and bananas) and vegetables (potatoes and lettuces) fortified at the microg kg(-1) level were in the interval 93-102%. PMID:19720194

Moral, Antonia; Sicilia, María Dolores; Rubio, Soledad

2009-09-21

390

A liposomal fluorescence assay to study permeation kinetics of drug-like weak bases across the lipid bilayer.  

PubMed

Lipid bilayer permeation is considered the major route for in vivo barrier passage of drugs. Despite this fact, no technique is currently available to measure the kinetics of permeation across a single lipid bilayer of structurally unrelated drug-like solutes. We developed a liposomal fluorescence assay capable to determine permeation kinetics of basic drug-like solutes across lipid bilayers. The assay is based on the hypothesis that permeation of a weak base along a concentration gradient results in net proton release at the cis-side and net proton capture at the trans-side of the bilayer. The resulting pH changes were monitored with pH-sensitive fluorophores: Test compounds were incubated with liposomes containing a pH-sensitive fluorophore at the bilayer surfaces or in the aqueous lumen and fluorescence changes were monitored with a stopped-flow apparatus in solution or by total internal reflection fluorescence microscopy with surface-captured liposomes on a microfluidic platform. Incubation with lipophilic basic drugs resulted in the expected fluorescence changes while incubation with compounds without basic functionality or high polarity did not affect fluorescence. Kinetics of fluorescence changes followed bi-exponential functions. Logarithmic permeation coefficients (logPermapp) determined in solution and by microfluidics technology showed a good correlation (r(2)=0.94, n=7) and logPermapp increased with increasing lipophilicity. Neither diffusion in the aqueous phase nor partitioning into the bilayer was rate-limiting. PEGylation of 2% of the liposomal lipids reduced Permapp by a factor ~300. In conclusion, the presented liposomal fluorescence assay is capable to determine permeation kinetics of weak basic drug-like solutes across lipid bilayers. The method is adaptable to microfluidics technology for high-throughput measurements and can potentially be modified to work for weak acid solutes. PMID:24211703

Eyer, Klaus; Paech, Franziska; Schuler, Friedrich; Kuhn, Phillip; Kissner, Reinhard; Belli, Sara; Dittrich, Petra S; Krämer, Stefanie D

2014-01-10

391

Using simple agent-based modeling to inform and enhance neighborhood walkability  

PubMed Central

Background Pedestrian-friendly neighborhoods with proximal destinations and services encourage walking and decrease car dependence, thereby contributing to more active and healthier communities. Proximity to key destinations and services is an important aspect of the urban design decision making process, particularly in areas adopting a transit-oriented development (TOD) approach to urban planning, whereby densification occurs within walking distance of transit nodes. Modeling destination access within neighborhoods has been limited to circular catchment buffers or more sophisticated network-buffers generated using geoprocessing routines within geographical information systems (GIS). Both circular and network-buffer catchment methods are problematic. Circular catchment models do not account for street networks, thus do not allow exploratory ‘what-if’ scenario modeling; and network-buffering functionality typically exists within proprietary GIS software, which can be costly and requires a high level of expertise to operate. Methods This study sought to overcome these limitations by developing an open-source simple agent-based walkable catchment tool that can be used by researchers, urban designers, planners, and policy makers to test scenarios for improving neighborhood walkable catchments. A simplified version of an agent-based model was ported to a vector-based open source GIS web tool using data derived from the Australian Urban Research Infrastructure Network (AURIN). The tool was developed and tested with end-user stakeholder working group input. Results The resulting model has proven to be effective and flexible, allowing stakeholders to assess and optimize the walkability of neighborhood catchments around actual or potential nodes of interest (e.g., schools, public transport stops). Users can derive a range of metrics to compare different scenarios modeled. These include: catchment area versus circular buffer ratios; mean number of streets crossed; and modeling of different walking speeds and wait time at intersections. Conclusions The tool has the capacity to influence planning and public health advocacy and practice, and by using open-access source software, it is available for use locally and internationally. There is also scope to extend this version of the tool from a simple to a complex model, which includes agents (i.e., simulated pedestrians) ‘learning’ and incorporating other environmental attributes that enhance walkability (e.g., residential density, mixed land use, traffic volume). PMID:24330721

2013-01-01

392

Anatomy-Based Algorithms for Detecting Oral Cancer Using Reflectance and Fluorescence Spectroscopy  

E-print Network

OBJECTIVES: We used reflectance and fluorescence spectroscopy to noninvasively and quantitatively distinguish benign from dysplastic/malignant oral lesions. We designed diagnostic algorithms to account for differences in ...

McGee, Sasha

393

Fluorescent sensor for selective detection of Al(3+) based on quinoline-coumarin conjugate.  

PubMed

A fluorescence probe, 8-formyl-7-hydroxyl-4-methyl coumarin - (2'-methylquinoline-4-formyl) hydrazone (L) has been synthesized. The chemosensor is found preferential binding to Al(3+) in presence of other competitive ions with associated changes in its optical and fluorescence spectra behavior. Upon addition of Al(3+) to a solution of L, it shows 200-fold enhancement of fluorescence intensity which might be attributed to form a 2:1 stoichiometry of the binding mode of LAl(III) and the chelation enhanced fluorescence (CHEF) process at 479nm in ethanol. The lowest detection limit for Al(3+) is determined as 8.2×10(-7)M. PMID:24929313

Qin, Jing-can; Li, Tian-rong; Wang, Bao-dui; Yang, Zheng-yin; Fan, Long

2014-12-10

394

A new and simple method to determine trace levels of sulfonamides in honey by high performance liquid chromatography with fluorescence detection.  

PubMed

A novel method for the simultaneous analysis at trace level of sulfonamides (sulfaguanidine, sulfanilamide, sulfacetamide, sulfathiazole, sulfapyridine, sulfachloropyridazine, sulfamerazine, sulfameter, sulfamethazine, sulfadoxine, sulfadiazine, sulfamonomethoxine, sulfadimethoxine) in honey is described. Methanol has been used in the sample treatment step to avoid the emulsion formation and to break the N-glycosidic bond between sugars and sulfonamides. The determination is carried out by liquid chromatography in gradient elution mode, with fluorescence detection after the on-line pre-column derivatization with fluorescamine. The influence of parameters such as the mobile phase composition, column temperature, pH or injection volume, on the separation has been taken into account and the derivatization step has also been optimized. Recoveries of the compounds on spiked honey samples ranged from 56% for sulfadoxine to 96% for sulfacetamide, with relative standard deviations below 10%. The quantitation limits are between 4 and 15 ng g(-1). PMID:19505691

Bernal, José; Nozal, María Jesús; Jiménez, Juan José; Martín, María Teresa; Sanz, Esther

2009-10-23

395

A simple model of circadian rhythms based on dimerization and proteolysis of PER and TIM  

PubMed Central

Many organisms display rhythms of physiology and behavior that are entrained to the 24-h cycle of light and darkness prevailing on Earth. Under constant conditions of illumination and temperature, these internal biological rhythms persist with a period close to 1 day ("circadian"), but it is usually not exactly 24 h. Recent discoveries have uncovered stunning similarities among the molecular circuitries of circadian clocks in mice, fruit flies, and bread molds. A consensus picture is coming into focus around two proteins (called PER and TIM in fruit flies), which dimerize and then inhibit transcription of their own genes. Although this picture seems to confirm a venerable model of circadian rhythms based on time-delayed negative feedback, we suggest that just as crucial to the circadian oscillator is a positive feedback loop based on stabilization of PER upon dimerization. These ideas can be expressed in simple mathematical form (phase plane portraits), and the model accounts naturally for several hallmarks of circadian rhythms, including temperature compensation and the per(L) mutant phenotype. In addition, the model suggests how an endogenous circadian oscillator could have evolved from a more primitive, light-activated switch. PMID:20540926

Tyson, JJ; Hong, CI; Thron, CD; Novak, B

1999-01-01

396

Selective turn-on fluorescence for Zn(2+) and Zn(2+)+Cd(2+) metal ions by single Schiff base chemosensor.  

PubMed

Chemosensor based on Schiff base molecules (1, 2) were synthesized and demonstrated the selective fluoro/colorimetric sensing of multiple metal ions (Mn(2+), Zn(2+) and Cd(2+)) in acetonitrile-aqueous solution. Both 1 and 2 showed a highly selective naked-eye detectable colorimetric change for Mn(2+) ions at 10(-7)M. Fluorescence sensing studies of 1 and 2 exhibited a strong fluorescence enhancement (36 fold) selectively upon addition of Zn(2+) (10(-7)M, ?max=488nm). Fluorescence titration and single crystal X-ray analysis confirmed the formation of 1:1 molecular coordination complex between 1 and Zn(2+). Interestingly, a rare phenomenon of strong second turn-on fluorescence (190 fold, ?max=466nm) was observed by the addition of Cd(2+) (10(-7)M) into 1+Zn(2+) or Zn(2+) (10(-7)M) into 1+Cd(2+). Importantly both 1 and 2 exhibited different fluorescence ?max with clearly distinguishable color for both Zn(2+) and Cd(2+). PMID:25263119

Hariharan, P S; Anthony, Savarimuthu Philip

2014-10-27

397

Fluorescent detection of Southern blots and PCR-based genetic typing tests  

SciTech Connect

The Southern blot is used to study gene organization, to identify disease-causing genomic rearrangements, or for typing RFLP markers in forensic, paternity, or prenatal diagnostic testing. Fluorescence offers a much greater dynamic range and a more linear response than film used in radioactive or chemiluminescent detection of RFLPs. We therefore investigated using the Fluorimager{trademark} 575 (Molecular Dynamics, Inc.) for analyzing Southern blots. Using a single-locus probe to D2S44 (YNH24) (Promega Corp.), we detect as little as 100 ng (0.05 attomole) genomic DNA. The alkaline phosphatase-labeled probe is detected using AttoPhos (JBL Scientific), and the developed membrane is scanned with the Fluorimager. Biotinylated hybridization probes can also be developed using a streptavidin-alkaline phosphatase conjugate and AttoPhos. The instrument scan parameters can be adjusted to prevent overexposure and accompanying loss of resolution in images of blots, gels, or 96-well microplates. We have used these other sample formats in PCR-based genetic typing assays. We use FluorKit DQS (Molecular Dynamics) to accurately quantify PCR template DNA (1-500 ng) in 96-well microplates scanned using the same instrument. Mutation detection assays run include heteroduplex gels (5% polyacrylamide, 2.7 M urea), short tandem repeat (STR) markers, amplified fragment length polymorphisms (AmpFLP), competitive priming PCR, and allele-specific oligotyping. These assays are run using either 1- or 2-color labeling. We detect unlabeled PCR products, such as the AmpFLP marker D1S80 (Perkin-Elmer) by post-staining gels for 10 minutes with SYBR Green 1 (Molecular Probes) and scanning the wet gel. The Fluorimager scans a 20 x 25 cm sample within three minutes, allowing rapid optimization of fluorescent protocols and high sample throughput.

Mansfield, E.S.; Worley, J.M. [Molecular Dynamics, Inc., Sunnyvale, CA (United States); Zimmerman, P.A. [Laboratory of Parasitic Diseases, Bethesda, MD (United States)] [and others

1994-09-01

398

Fluorescent refrigeration  

DOEpatents

Fluorescent refrigeration is based on selective radiative pumping, using substantially monochromatic radiation, of quantum excitations which are then endothermically redistributed to higher energies. Ultimately, the populated energy levels radiatively deexcite emitting, on the average, more radiant energy than was initially absorbed. The material utilized to accomplish the cooling must have dimensions such that the exciting radiation is strongly absorbed, but the fluorescence may exit the material through a significantly smaller optical pathlength. Optical fibers and mirrored glasses and crystals provide this requirement. 6 figs.

Epstein, R.I.; Edwards, B.C.; Buchwald, M.I.; Gosnell, T.R.

1995-09-05

399

Fluorescent Ru(phen)3(2+)-doped silica nanoparticles-based ICTS sensor for quantitative detection of enrofloxacin residues in chicken meat.  

PubMed

A Ru(phen)3(2+)-doped silica fluorescent nanoparticle (FN)-based immunochromatographic test strip (ICTS) sensor was developed for rapid, high sensitivity, easy to use, and low cost quantitative detection of enrofloxacin (ENR) residues in chicken meat. The fluorescence signal intensity of the FNs at the test line (FI(T)) and control line (FI(C)) was determined with a prototype of a portable fluorescent strip reader. Unique properties of Ru(phen)3(2+) doped silica nanoparticles (e.g., large Stokes shift, high emission quantum yield, and long fluorescence lifetime) were combined with the advantages of ICTS and an easy to make portable fluorescent strip reader. The signal was based on FI(T)/FI(C) ratio to effectively eliminate strip to strip variation and matrix effects. Various parameters that influenced the strip were investigated and optimized. Quantitative ENR detection with the FNs ICTS sensor using 80 ?L sample took only 20 min, which is faster than the commercial ELISA kit (that took 90 min). The linear range of detection in chicken extract was established at 0.025-3.500 ng/mL with a half maximal inhibitory concentration at 0.22 ± 0.02 ng/mL. Using the optimized parameters, the limit of detection (LOD) for ENR using the FNs ICTS sensor was recorded at 0.02 ng/mL in chicken extract. This corresponds to 0.12 ?g/kg chicken meat which is two (2) orders of magnitude better that the maximum residue limits (MRLs) imposed in Japan (10 ?g/kg) and three (3) orders of magnitude better than those imposed in China. The intra- and inter-assay coefficient of variations (CVs) were 6.04% and 12.96% at 0.5 ng/mL, 6.92% and 12.61% at 1.0 ng/mL, and 6.66% and 11.88% at 2.0 ng/mL in chicken extract, respectively. The recoveries using the new FNs ICTS sensor from fifty (50) ENR-spiked chicken samples showed a highly significant correlation (R(2) = 0.9693) with the commercial enzyme-linked immunosorbent assay (ELISA) kit. The new FNs ICTS sensor is a simple, rapid, sensitive, accurate, and inexpensive quantitative detection of ENR residues in chicken meat and extracts. PMID:23614687

Huang, Xiaolin; Aguilar, Zoraida P; Li, Huaiming; Lai, Weihua; Wei, Hua; Xu, Hengyi; Xiong, Yonghua

2013-05-21

400

Detection of C-reactive protein based on magnetic nanoparticles and capillary zone electrophoresis with laser-induced fluorescence detection.  

PubMed

A simple and fast method based on magnetic nanoparticles (MNPs) and capillary zone electrophoresis (CZE) with laser-induced fluorescence (LIF) detection was developed for the detection of C-reactive protein (CRP). To optimize the CZE conditions, several factors including buffer compositions, buffer ionic strength, buffer pH, applied voltage and capillary temperature have been examined. The optimal separation buffer selected was a 30 mM sodium phosphate (PB) buffer, pH 8.0. The optimal CE applied voltage and temperature selected were 20 kV and 35°C, respectively. The CZE profile of the MNP-1°Ab-CRP-2°Ab/FITC bioconjugates showed good reproducibility. One major peak was observed for the MNP bioconjugates. The quantitative analysis also showed good results. The coefficient of variation (CV%) for the major peak area was 8.7%, and the CV% for the major peak migration time was 2.5%. The linear range for CRP analysis was 10-150 ?g/mL, and the concentration limit of detection (LOD) was 9.2 ?g/mL. Non-specific interactions between bovine serum albumin (BSA) and the system can be prevented by including 10% (v/v) of human plasma in the binding buffers. The CE/LIF method might be helpful for analyzing high concentrations of CRP in a patient's plasma after an acute-phase inflammation. This new method demonstrated the possibility of using MNPs and CE/LIF for the detection of proteins, and provided information for the establishment of appropriate CE conditions. PMID:24075015

Lin, Yi-Jyun; Yang, Jian-Ying; Shu, Ting-Yu; Lin, Ting-Yu; Chen, Yen-Yi; Su, Mei-Yu; Li, Wen-Jie; Liu, Mine-Yine

2013-11-01

401

A Schiff-based sensor with turn-on fluorescence for selective detection of Hg2+.  

PubMed

A simple Schiff-base colorimetric receptor 1 was prepared. It exhibits an ‘off–on-type’ mode with high sensitivity in the presence of Hg2+. The change in color is very easily observed by the naked eye in the presence of Hg2+, whereas other metal cations do not induce such a change. A Job plot indicated a 1 : 1 complexation stoichiometry between receptor 1 and Hg2+. The association constant for 1–Hg2+ in Tetrahydrofuran (THF) was determined to be 1.3 × 10(9)M-1 using a Hill plot. PMID:25337615

Wan, Chin-Feng; Lin, Hsiang-Yi; Chien, Cho; Wu, An-Tai

2014-09-01

402

Delta alkalinity: a simple method to measure cellular net acid-base fluxes.  

PubMed

Acid-base transport across cell plasma membranes is important for cell homeostasis and growth. Current techniques for quantitatively measuring net acid-base fluxes are generally limited by either assumptions concerning properties of intracellular compartments or use of poorly buffered, nonphysiological solutions. We adapted an approach from marine chemistry to quantitate net acid-base changes in standard physiological media that obviates these problems. This method is based on conservation of charge and involves a simple acid titration of the extracellular medium to an end point, the equivalence point, pHe. For standard physiological solutions containing buffers such as bicarbonate and phosphate, pHe exists in the range of pH 4.0-4.7 and is identified as the pH where dpH/dH+ is maximal in an HCl titration. By determining the quantity of H+ required to reach pHe, one can determine precisely total quantity of proton acceptors (alkalinity) present in physiological pH range. Alkalinity (in meq) is a relative measure of the charge capable of interacting with protons. We show that, unlike pH, changes in alkalinity (delta alkalinity) result only from net acid-base changes in medium. Therefore, by monitoring extracellular delta alkalinity associated with cell function, it is possible to quantitate precisely net acid-base fluxes. Moreover, through a second titration procedure, delta alkalinity can be divided into bicarbonate and nonbicarbonate fractions. As an example, we performed the first direct measurement of net Cl(-)-HCO3- exchange in intact human erythrocytes and observed a Cl(-)-HCO3- exchange ratio of 1.01 +/- 0.03. Overall, delta alkalinity measurements are applicable to numerous cell systems, can be performed with solutions containing a mixture of buffers at normal physiological concentrations (e.g., 25 mM HCO3- and 2 mM HPO4(-2), do not require corrections for CO2 diffusion or loss of CO2 from the solution, and avoid assumptions about intracellular or extracellular buffer properties. PMID:3116853

Burbea, Z H; Gullans, S R; Ben-Yaakov, S

1987-10-01

403

A finite-element-based reconstruction method for 3D fluorescence tomography  

E-print Network

a dual-excitation-mode methodology for three-dimensional (3D) fluorescence molecular tomography (FMT imaging: noninvasive in vivo biolumines- cent and fluorescent optical Imaging in Cancer Research," Mol. Phys. 32, 992­1000 (2005). 13. W. Cong, D. Kumar, Y. Liu, A. Cong, and G. Wang, "A practical method

Virginia Tech

404

Pesticide Residues Detection by Fluorescence Spectral Analysis Based on BP Neural Network  

Microsoft Academic Search

At present, it is a difficulty to achieve rapid and accurate detection to pesticide residues. In the paper, an overlapped spectrum in fluorescence spectroscopy measurements of acetamiprid residues was separated using artificial neural networks. By means of artificial neural network principle and back-propagation training algorithm, acetamiprid concentration were determined in mixed component of residues and filter paper with overlapped fluorescence

Wang Lei; Qiao Xiaoyan

2010-01-01

405

Platinum plasmonic nanostructure arrays for massively parallel single-molecule detection based on enhanced fluorescence measurements.  

PubMed

We fabricated platinum bowtie nanostructure arrays producing fluorescence enhancement and evaluated their performance using two-photon photoluminescence and single-molecule fluorescence measurements. A comprehensive selection of suitable materials was explored by electromagnetic simulation and Pt was chosen as the plasmonic material for visible light excitation near 500 nm, which is preferable for multicolor dye-labeling applications like DNA sequencing. The observation of bright photoluminescence (? = 500-600 nm) from each Pt nanostructure, induced by irradiation at 800 nm with a femtosecond laser pulse, clearly indicates that a highly enhanced local field is created near the Pt nanostructure. The attachment of a single dye molecule was attempted between the Pt triangles of each nanostructure by using selective immobilization chemistry. The fluorescence intensities of the single dye molecule localized on the nanostructures were measured. A highly enhanced fluorescence, which was increased by a factor of 30, was observed. The two-photon photoluminescence intensity and fluorescence intensity showed qualitatively consistent gap size dependence. However, the average fluorescence enhancement factor was rather repressed even in the nanostructure with the smallest gap size compared to the large growth of photoluminescence. The variation of the position of the dye molecule attached to the nanostructure may influence the wide distribution of the fluorescence enhancement factor and cause the rather small average value of the fluorescence enhancement factor. PMID:21988776

Saito, Toshiro; Takahashi, Satoshi; Obara, Takayuki; Itabashi, Naoshi; Imai, Kazumichi

2011-11-01

406

Context based mixture model for cell phase identification in automated fluorescence microscopy  

Microsoft Academic Search

Background: Automated identification of cell cycle phases of individual live cells in a large population captured via automated fluorescence microscopy technique is important for cancer drug discovery and cell cycle studies. Time-lapse fluorescence microscopy images provide an important method to study the cell cycle process under different conditions of perturbation. Existing methods are limited in dealing with such time-lapse data

Meng Wang; Xiaobo Zhou; Randy W. King; Stephen T. C. Wong

2007-01-01

407

Simple HPLC Detector for the Detection of NIR Dyes  

Microsoft Academic Search

The development and evaluation of a simple, silicon photodiode-based near infrared HPLC detector is presented. The instrument was evaluated using dyes fluorescing in the near infrared region. It was found to have sensitivity comparable with those based on sensors built around high voltage photmultiplier tubes.

Peter Kuklenyik; Gabor Patonay

1995-01-01