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1

A new simple Schiff base fluorescence "on" sensor for Al(3+) and its living cell imaging.  

PubMed

The simple Schiff base (Z)-N-benzylidenenaphthalen-1-amine () acts as an effective fluorescence sensor for Al(3+) by "off-on" mode, and ca. 42 times enhancement in fluorescence intensity is observed. The detection limit of towards Al(3+) is observed to be 5 × 10(-5) M. UV/Visible and fluorescence data as well as DFT calculations confirm 1?:?3 coordination between Al(3+) and through N atoms in a pyramidal shape. is employed for imaging the Al(3+) ion in living biological cells and for the determination of the Al(3+) ion in bovine serum albumin. PMID:25652390

Kumar, Jutika; Sarma, Manas Jyoti; Phukan, Prodeep; Das, Diganta Kumar

2015-02-24

2

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

PubMed

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

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

2014-09-15

3

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

PubMed

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

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

2015-02-15

4

A simple and sensitive fluorescent sensor for methyl parathion based on l-tyrosine methyl ester functionalized carbon dots.  

PubMed

In this paper, a simple and sensitive fluorescent sensor for methyl parathion is developed based on l-tyrosine methyl ester functionalized carbon dots (Tyr-CDs) and tyrosinase system. The carbon dots are obtained by simple hydrothermal reaction using citric acid as carbon resource and l-tyrosine methyl ester as modification reagent. The carbon dots are characterized by transmission electron microscope, high resolution transmission electron microscopy, X-ray diffraction spectrum, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The carbon dots show strong and stable photoluminescence with a quantum yield of 3.8%. Tyrosinase can catalyze the oxidation of tyrosine methyl ester on the surface of carbon dots to corresponding quinone products, which can quench the fluorescence of carbon dots. When organophosphorus pesticides (OPs) are introduced in system, they can decrease the enzyme activity, thus decrease the fluorescence quenching rate. Methyl parathion, as a model of OPs, was detected. Experimental results show that the enzyme inhibition rate is proportional to the logarithm of the methyl parathion concentration in the range 1.0×10(-10)-1.0×10(-4)M with the detection limit (S/N=3) of 4.8×10(-11)M. This determination method shows a low detection limit, wide linear range, good selectivity and high reproducibility. This sensing system has been successfully used for the analysis of cabbage, milk and fruit juice samples. PMID:25558870

Hou, Juying; Dong, Jing; Zhu, Haishuang; Teng, Xue; Ai, Shiyun; Mang, Minglin

2015-06-15

5

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

6

A new simple cell-based homogeneous time-resolved fluorescence QRET technique for receptor-ligand interaction screening.  

PubMed

In this article, a single-label separation-free fluorescence technique is presented as a potential screening method for cell-based receptor antagonists and agonists.The time-resolved fluorescence technique, quenching resonance energy transfer (QRET), relies on a single-labeled binding partner in combination with a soluble quencher. The quencher efficiently suppresses the luminescence of the unbound labeled ligand, whereas the luminescence of the bound fraction is not affected. This approach allows the development of cell-based screening assays in a simple and cost-effective manner. The authors have applied the technique to the screening of beta(2)-adrenoreceptor (beta(2)AR) antagonists and agonists in intact human embryonic kidney HEK293(i) cells overexpressing human beta(2)-adrenergic receptors. Two antagonists (propranolol, alprenolol) and 2 agonists (metaproterenol, terbutaline) for beta(2)AR were investigated in a displacement assay using europium(III)-labeled pindolol ligand. The assay Z' values ranged from 0.68 to 0.78, the coefficient of variation was less than 10%, and the K(i) values were 19 nM for propranolol and alprenolol and 14 and 5.9 microM for metaproterenol and terbutaline, respectively. The QRET technique with beta(2)AR was also applied to LOPAC compound library screening, yielding nearly error-free recognition of known binders. This simple and cost-effective technique can be readily adapted to laboratory and industrial-scale screening. PMID:19684287

Härmä, Harri; Rozwandowicz-Jansen, Anita; Martikkala, Eija; Frang, Heini; Hemmilä, Ilkka; Sahlberg, Niko; Fey, Vidal; Perälä, Merja; Hänninen, Pekka

2009-09-01

7

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

8

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

9

Selective fluorescence sensing of Cu(II) and Zn(II) using a simple Schiff base ligand: Naked eye detection and elucidation of photoinduced electron transfer (PET) mechanism.  

PubMed

A simple Schiff base compound 2-((cyclohexylmethylimino)-methyl)-naphthalen-1-ol (2CMIMN1O) has been synthesized and characterized by (1)H NMR, (13)C NMR and FT-IR spectroscopic techniques. A significantly low emission yield of the compound has been rationalized in anticipation with photo-induced electron transfer (PET) from the imine receptor moiety to the naphthalene fluorophore unit. Consequently, an evaluation of the transition metal ion-induced modification of the fluorophore-receptor communication reveals the promising prospect of the title compound to function as a chemosensor for Cu(2+) and Zn(2+) ions selectively, through remarkable fluorescence enhancement as well as visual changes. While perturbation of the PET process has been argued to be the plausible mechanism behind the fluorescence enhancement, the selectivity for these two metal ions has been interpreted on the grounds of an appreciably strong binding interaction. Particularly notable aspects regarding the chemosensory activity of the compound is its ability to detect the aforesaid transition metal ions down to the level of micromolar concentration (detection limit being 2.74 and 2.27ppm respectively), along with a simple and efficient synthetic procedure. PMID:25721777

Ganguly, Aniruddha; Ghosh, Soumen; Kar, Samiran; Guchhait, Nikhil

2015-05-15

10

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

PubMed

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

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

2014-02-15

11

Simple Time-Saving Method for Iron Determination Based on Fluorescence Quenching of an Azaflavanon-3-ol Compound.  

PubMed

A simple and time-saving spectrofluorometric method developed using an azaflavanon-3-ol compound was used for the determination of iron in various food samples. Nitric acid and hydrogen peroxide were used for digestion of samples in a closed microwave system. The method was validated by analyzing two certified reference materials (CRM-SA-C Sandy Soil C and Mixed Polish Herbs INCT-MPH-2). Measurements were carried out using a modified standard addition method. The standard addition graph was linear until 21.6 mg/L in the determination of iron(III). Detection and quantification limits were 0.81 and 2.4 mg/L, respectively. Satisfactory accuracy was obtained for spinach, dill, mint, purslane, rocket, red lentils, dry beans, and two iron medicinal tablets. High recoveries were found for streamwater samples fortified at three different concentrations. The method is simple, time-saving, cost-effective, and suitable for the determination of the iron content of foods. PMID:25723252

Ba?o?lu, Aysel; Tosun, Gonca; Ocak, Miraç; Alp, Hakan; Yayl?, Nurettin; Ocak, Ümmühan

2015-03-18

12

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

13

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 0.34-0.73 ng/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

14

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

PubMed

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

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

2015-06-01

15

A simple PCR-based fluorometric system for detection of mutant fusion DNAs using a quencher-free fluorescent DNA probe and graphene oxide.  

PubMed

We propose a facile fluorometric system for detection of gene mutations using graphene oxide (GO). A fluorescent probe DNA anneals to a specific mutant gene and is degraded by the 5'? 3' exonuclease activity of Taq polymerase during PCR, and the released fluorophore retains fluorescence after addition of GO without quenching. PMID:25797656

Roh, Kyoungmin; Kim, Dong-Min; Lee, Eun Hee; Kim, Hyoseon; Park, Hyung Soon; Jang, Ja-Hyun; Hwang, Sang-Hyun; Kim, Dong-Eun

2015-04-25

16

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

PubMed

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

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

2015-05-15

17

Fluorescent sensors based on bacterial fusion proteins  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

18

Plant genotyping using fluorescently tagged inter-simple sequence repeats (ISSRs): basic principles and methodology.  

PubMed

Inter-simple sequence repeat PCR (ISSR-PCR) is a fast, inexpensive genotyping technique based on length variation in the regions between microsatellites. The method requires no species-specific prior knowledge of microsatellite location or composition. Very small amounts of DNA are required, making this method ideal for organisms of conservation concern, or where the quantity of DNA is extremely limited due to organism size. ISSR-PCR can be highly reproducible but requires careful attention to detail. Optimization of DNA extraction, fragment amplification, and normalization of fragment peak heights during fluorescent detection are critical steps to minimizing the downstream time spent verifying and scoring the data. PMID:25373749

Prince, Linda M

2015-01-01

19

Ultrasound-modulated fluorescence based on fluorescent microbubbles  

NASA Astrophysics Data System (ADS)

Ultrasound-modulated fluorescence (UMF) imaging has been proposed to provide fluorescent contrast while maintaining ultrasound resolution in an optical-scattering medium (such as biological tissue). The major challenge is to extract the weakly modulated fluorescent signal from a bright and unmodulated background. UMF was experimentally demonstrated based on fluorophore-labeled microbubble contrast agents. These contrast agents were produced by conjugating N-hydroxysuccinimide (NHS)-ester-attached fluorophores on the surface of amine-functionalized microbubbles. The fluorophore surface concentration was controlled so that a significant self-quenching effect occurred when no ultrasound was applied. The intensity of the fluorescent emission was modulated when microbubbles were oscillated by ultrasound pulses, presented as UMF signal. Our results demonstrated that the UMF signals were highly dependent on the microbubbles' oscillation amplitude and the initial surface fluorophore-quenching status. A maximum of ˜42% UMF modulation depth was achieved with a single microbubble under an ultrasound peak-to-peak pressure of 675 kPa. Further, UMF was detected from a 500-?m tube filled with contrast agents in water and scattering media with ultrasound resolution. These results indicate that ultrasound-modulated fluorescent microbubble contrast agents can potentially be used for fluorescence-based molecular imaging with ultrasound resolution in the future.

Liu, Yuan; Feshitan, Jameel A.; Wei, Ming-Yuan; Borden, Mark A.; Yuan, Baohong

2014-08-01

20

A fluorescence high-temperature sensor based on fluorescence lifetime  

NASA Astrophysics Data System (ADS)

A kind of fluorescence optic-fiber temperature sensor is devised based on the alexandrite crystal. In this system, a new optic- fiber probe fabrication techniques is proposed. This system is particularly adapted to the temperature measurement in the range of room temperature to 650°C. During the cause of experimentation, using the PLD-PMTR (termed the Pulse Modulated Phase-locked detection with Two References) signal processing scheme. This temperature measurement method is proved to be effective and useful for its highly resolution and precision. It ensured the detected fluorescence signal to noise ratio was high enough to be measurable when the temperature is raised to 650°C.

Wu, Jinling; Wang, Yutian; Wang, Xinian

2006-11-01

21

Simple logarithmic time base generator  

Microsoft Academic Search

A digital device containing only three inexpensive CMOS chips is described that can generate the log-time function over seven decades of time. Simple modifications that can increase the range and the accuracy are also described.

E. F. Denby; L. J. Wills

1978-01-01

22

Simple logarithmic time base generator.  

PubMed

A digital device containing only three inexpensive CMOS chips is described that can generate the log-time function over seven decades of time. Simple modifications that can increase the range and the accuracy are also described. PMID:18699075

Denby, E F; Wills, L J

1978-02-01

23

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

24

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

PubMed

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

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

2014-01-01

25

Fluorescence polarization immunoassays and related methods for simple, high-throughput screening of small molecules  

Microsoft Academic Search

Fluorescence polarization immunoassay (FPIA) is a homogeneous (without separation) competitive immunoassay method based on\\u000a the increase in fluorescence polarization (FP) of fluorescent-labeled small antigens when bound by specific antibody. The\\u000a minimum detectable quantity of FPIAs with fluorescein label (about 0.1 ng analyte) is comparable with chromatography and ELISA\\u000a methods, although this may be limited by sample matrix interference. Because of its

David S. Smith; Sergei A. Eremin

2008-01-01

26

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

Microsoft Academic Search

A simple and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the determination of five different quinolones: enrofloxacin, ciprofloxacin, sarafloxacin, oxolinic acid and flumequine in pork and salmon muscle. The method includes one extraction and clean-up step for the five quinolones together which are detected in two separated HPLC runs by means of their fluorescence. The proposed analytical

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

2003-01-01

27

Competitive Quenching Fluorescence Immunoassay for Chlorophenols Based on  

E-print Network

Competitive Quenching Fluorescence Immunoassay for Chlorophenols Based on Laser microdroplets by a homogeneous quenching fluorescence immunoassay (QFIA). The competitive immunoassay oc- curs the opportunity for miniaturization and high- throughput screening. Fluorescence immunoassays (fluoroimmu

Hammock, Bruce D.

28

A FRET-based analysis of SNPs without fluorescent probes  

PubMed Central

Fluorescence resonance energy transfer (FRET) is a simple procedure for detecting specific DNA sequences, and is therefore used in many fields. However, the cost is relatively high, because FRET-based methods usually require fluorescent probes. We have designed a cost-effective way of using FRET, and developed a novel approach for the genotyping of single nucleotide polymorphisms (SNPs) and allele frequency estimation. The key feature of this method is that it uses a DNA-binding fluorogenic molecule, SYBR Green I, as an energy donor for FRET. In this method, single base extension is performed with dideoxynucleotides labeled with an orange dye and a red dye in the presence of SYBR Green I. The dyes incorporated into the extended products accept energy from SYBR Green I and emit fluorescence. We have validated the method with ten SNPs, which were successfully discriminated by end-point measurements of orange and red fluorescence intensity in a microplate fluorescence reader. Using a mixture of homozygous samples, we also confirmed the potential of this method for estimation of allele frequency. Application of this strategy to large-scale studies will reduce the time and cost of genotyping a vast number of SNPs. PMID:15534363

Takatsu, Kyoko; Yokomaku, Toyokazu; Kurata, Shinya; Kanagawa, Takahiro

2004-01-01

29

Line laser beam based laser-induced fluorescence detection system for microfluidic chip electrophoresis analysis  

Microsoft Academic Search

In this work, a new laser-induced fluorescence (LIF) detection system based on a line laser beam for microfluidic chip electrophoresis analysis was developed. This detection system had the advantages of simple optical structure, compactness, and ease in constructing. Highly sensitive detection was realized by detecting the fluorescence light emitted in the micro-channel through the vertical intersection between the line laser

Baojian Xu; Mo Yang; Hua Wang; Honglian Zhang; Qinghui Jin; Jianlong Zhao; Huimin Wang

2009-01-01

30

Ultrasensitive turn-on fluorescent detection of trace thiocyanate based on fluorescence resonance energy transfer.  

PubMed

Thiocyanate (SCN(-)) is a small anion byproduct of cyanide metabolism. Several methods have been reported to measure SCN(-) above the micromolar level. However, SCN(-) is derived from many sources such as cigarettes, waste water, food and even car exhaust and its effect is cumulative, which makes it necessary to develop methods for the detection of trace SCN(-). In this paper, a simple and ultrasensitive turn-on fluorescence assay of trace SCN(-) is established based on the fluorescence resonance energy transfer (FRET) between gold nanoparticles (AuNPs) and fluorescein. The detection limit is 0.09 nM, to the best of our knowledge, which has been the lowest detection LOD ever without the aid of costly instrumentation. The fluorescence of fluorescein is significantly quenched when it is attached to the surface of AuNPs. Upon the addition of SCN(-), the fluorescence is turned on due to the competition action between SCN(-) and fluorescein towards the surface of AuNPs. Under an optimum pH, AuNPs size and concentration, incubation time, the fluorescence enhancement efficiency [(IF-I0)/I0] displays a linear relationship with the concentration of SCN(-) in the range of 1.0 nM to 40.0 nM. The fluorescein-AuNP sensor shows absolutely high selectivity toward SCN(-) than other 16 anions. The common metal ions, amino acids and sugars have no obvious interference effects. The accuracy and precision were evaluated based on the recovery experiments. The cost effective sensing system is successfully applied for the determination of SCN(-) in milk products and saliva samples. PMID:25476353

Song, Juan; Wu, Fang-Ying; Wan, Yi-Qun; Ma, Li-Hua

2015-01-01

31

Fluorescent and colorimetric ion probes based on conjugated oligopyrroles.  

PubMed

Metal ions and anions play important roles in many industrial and biochemical processes, and thus it is highly desired to detect them in the relevant systems. Small organic molecule based sensors for selective and sensitive detection of target ions show the advantages of low cost, high sensitivity and convenient implementation. In this area, pyrrole has incomparable advantages. It can be easily incorporated into linear and macrocyclic conjugated structures such as dipyrrins, porphyrins, and N-confused porphyrins, which may utilize the imino N and amino NH moieties for binding metal ions and anions, respectively. In this tutorial review, we focus on representative examples to describe the design, syntheses, sensing mechanisms, and applications of the conjugated oligopyrroles. These compounds could be used as colorimetric or fluorescent ion probes, with the advantages of vivid colour and fluorescence changes, easy structural modification and functionalization, and tunable emission wavelengths. Compared with normal porphyrins, simple di- and tripyrrins, as well as some porphyrinoids are more suitable for designing fluorescence "turn-on" metal probes, because they may exhibit flexible confirmations, and metal coordination will improve the rigidity, resulting in vivid fluorescence enhancement. It is noteworthy that the oligopyrrolic moieties may simultaneously act as the binding unit as well as the reporting moiety, which simplifies the design and syntheses of the probes. PMID:25608833

Ding, Yubin; Tang, Yunyu; Zhu, Weihong; Xie, Yongshu

2015-03-01

32

Simple device for the direct visualization of oral-cavity tissue fluorescence  

NASA Astrophysics Data System (ADS)

Early identification of high-risk disease could greatly reduce both mortality and morbidity due to oral cancer. We describe a simple handheld device that facilitates the direct visualization of oral-cavity fluorescence for the detection of high-risk precancerous and early cancerous lesions. Blue excitation light (400 to 460 nm) is employed to excite green-red fluorescence from fluorophores in the oral tissues. Tissue fluorescence is viewed directly along an optical axis collinear with the axis of excitation to reduce inter- and intraoperator variability. This robust, field-of-view device enables the direct visualization of fluorescence in the context of surrounding normal tissue. Results from a pilot study of 44 patients are presented. Using histology as the gold standard, the device achieves a sensitivity of 98% and specificity of 100% when discriminating normal mucosa from severe dysplasia/carcinoma in situ (CIS) or invasive carcinoma. We envisage this device as a suitable adjunct for oral cancer screening, biopsy guidance, and margin delineation.

Lane, Pierre M.; Gilhuly, Terence; Whitehead, Peter D.; Zeng, Haishan; Poh, Catherine; Ng, Samson; Williams, Michelle; Zhang, Lewei; Rosin, Miriam; MacAulay, Calum E.

2006-03-01

33

A fluorescence-based rapid screening assay for cytotoxic compounds.  

PubMed

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

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

2004-12-24

34

A capillary-based probe for in situ detection of enhanced fluorescence signals  

NASA Astrophysics Data System (ADS)

A simple, compact, and high sensitivity capillary-based probe for the in situ detection of fluorescence signals with high sensitivity is demonstrated. A home-made single–multi-mode fiber coupler that is coaxially aligned with the capillary-based probe provides for the transmission of excitation light and the collection and transmission of fluorescence. We propose a conceptually straightforward theoretical model to optimize the factors affecting the fluorescence-capture capability of the capillary-based probe. The fluorescence signal detected by fiber-optic spectroscopy non-linearly increases with the length of the capillary-based probe. In addition, the thicker the capillary tube wall is, the less the fluorescence signals determined are. The performance of the proposed probe is evaluated experimentally by measuring the fluorescence spectra of Cy5.5 dye and blue-green algae. The experimental results show that the proposed probe provides more than a ten-fold increase in fluorescence signal compared with direct measurements by a flat-tipped multi-mode fiber probe. The advantages of the capillary-based probe, which include its simple and compact structure, excellent light collection efficiency, requirement of small sample volume, and recoverability of samples, allow its wide application to in situ detection in the medical, forensic, biological, geological, and environmental fields with high sensitivity.

Long, F.; Xiao, R.; Zhu, A. N.; Shi, H. C.; Wang, S. Q.

2013-07-01

35

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

NASA Astrophysics Data System (ADS)

A quinoline-based simple receptor (bis(2-quinolinylmethyl)benzylamine = 1) as a Zn2+ selective fluorescent chemosensor showed a large fluorescent enhancement with a blue shift in the presence of Zn2+ which is attributed to a chelation enhanced fluorescence (CHEF) effect with inhibition of a photoinduced electron transfer (PET) process of 1. In particular, this receptor could clearly distinguish Zn2+ from Cd2+. The binding mode of 1 and Zn2+ was found to be a 1:1 and confirmed by Job plot, 1H NMR titration and ESI-mass spectrometry analysis.

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

2014-01-01

36

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.

37

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

38

Simple, Script-Based Science Processing Archive  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

39

Kinetic determination of atrazine in foods based on stopped-flow fluorescence polarization immunoassay  

Microsoft Academic Search

A very simple and fast method for the direct determination of atrazine in food samples based on the use of stopped-flow fluorescence polarization immunoassay is described. Unlike other immunoassay methods where the analytical signal is obtained when the immunochemical reaction has reached or is close to the equilibrium, this method uses the initial rate of this reaction as the analytical

B Sendra; S Panadero; S Eremin; A Gómez-Hens

1998-01-01

40

Linear calibration function for optical oxygen sensors based on quenching of ruthenium fluorescence  

Microsoft Academic Search

A mathematical model is derived from the Stern–Volmer equation as a practical calibration function for various optical oxygen sensors based on quenching of ruthenium fluorescence. The model is simple and flexible, and is ideal for computing oxygen partial pressure from 0 to 760Torr in gaseous samples, and 0 to 200Torr in aqueous samples. Feasibility of this model for dissolved oxygen

Han Chuang; Mark A. Arnold

1998-01-01

41

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...

42

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...

43

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

44

A fluorescence lifetime-based solid sensor for water  

Microsoft Academic Search

A fluorescence lifetime-based water sensor was developed, based on a solvent-polarity-sensitive fluorescent metal-ligand compound, dipyridol[3,2-a:2?,3?-c]phenazine, di[cis-l,2-bis(diphenylphosphino)-ethylene] osmium(II) hexafluorophosphate, [Os(dppz)(dppe)2](PF6)2. When excited in acetone solution, the compound emitted orange-red fluorescence with a peak wavelength of 610 nm. Fluorescence quenching was observed from both intensity and lifetime measurements when water was presented in the acetone. To fabricate a water sensor, the compound

Qing Chang; Zakir Murtaza; Joseph R. Lakowicz; Govind Rao

1997-01-01

45

Fluorescence water sensor based on covalent immobilization of chalcone derivative  

Microsoft Academic Search

A new fluorescence sensor for determining water content in organic solvents has been successfully demonstrated based on a fluorescent dye. 4?-N,N-dimethylamino-4 methylacryloylamino chalcone (DMC), in which the charge donor and acceptor parts were both contained, was copolymerized with acrylamide, hydroxyethyl methacrylate and triethylene glycol dimethacrylate onto glass surface. The fluorescence intensity of DMC decreased with increasing of water content in

Cheng-Gang Niu; Ai-Ling Guan; Guang-Ming Zeng; Yun-Guo Liu; Zhong-Wu Li

2006-01-01

46

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

47

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

PubMed Central

Because of economic limitations, the cost-effective diagnosis of patients affected with rare microdeletion or microduplication syndromes is a challenge in developing countries. Here we report a sensitive, rapid, and affordable detection method that we have called Microdeletion/Microduplication Quantitative Fluorescent PCR (MQF-PCR). Our procedure is based on the finding of genomic regions with high homology to segments of the critical microdeletion/microduplication region. PCR amplification of both using the same primer pair, establishes competitive kinetics and relative quantification of amplicons, as happens in microsatellite-based Quantitative Fluorescence PCR. We used patients with two common microdeletion syndromes, the Williams-Beuren syndrome (7q11.23 microdeletion) and the 22q11.2 microdeletion syndromes and discovered that MQF-PCR could detect both with 100% sensitivity and 100% specificity. Additionally, we demonstrated that the same principle could be reliably used for detection of microduplication syndromes, by using patients with the Lubs (MECP2 duplication) syndrome and the 17q11.2 microduplication involving the NF1 gene. We propose that MQF-PCR is a useful procedure for laboratory confirmation of the clinical diagnosis of microdeletion/microduplication syndromes, ideally suited for use in developing countries, but having general applicability as well. PMID:23620743

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

2013-01-01

48

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

PubMed Central

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

Mukherjee, Arnab; Schroeder, Charles M.

2013-01-01

49

ZnO microrods to nanowalled microtubes: optimization using simple fluorescence microscopy and enhanced photocatalytic properties.  

PubMed

ZnO microtubes (MTs) of nanoscale wall thickness were prepared by synthesis of ZnO microrods (MRs) followed by etching the MRs to form MTs. ZnO MRs were synthesized by a simple solution growth method using zinc chloride and hexamine as precursors. Using KOH, ZnO MRs are etched into ZnO MTs. ZnO MTs were characterized by fluorescence microscopy (FM), X-ray diffraction, scanning electron microscopy, UV-Vis and photoluminescence spectroscopy. ZnO MTs have a diameter of ?600 nm, wall thickness of 30-40 nm and length of ?7 ?m. The influence of the KOH concentration and etching time on ZnO MRs for the formation of the ZnO MTs were studied. The formation of nanowalled ZnO tubes from ZnO MRs is optimized by simple and inexpensive FM imaging. FM was utilized as a tool to observe the changes in optical properties on change in morphology from ZnO MRs to MTs. FM images reveal that at low KOH concentration (0.125 M) the tubes were not completely etched whereas at higher concentration (0.375 M) the tube walls were damaged. Etchant concentration (0.125 M) and etching time of 12 h were found to be the optimized parameters for the realization of ZnO MTs using FM analysis. ZnO MTs were tested as the catalyst for the photodegradation of the methylene blue dye. The result shows that the photodegradation efficiency of the tubes is twice as fast as compared to that of rods. PMID:24102620

Ranjith, K S; Kiruthika, B; Rajendrakumar, R T

2013-12-01

50

Boronate-Based Fluorescent Probes for Imaging Cellular Hydrogen Peroxide  

E-print Network

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

Pralle, Arnd

51

Ratiometric biosensors based on dimerization-dependent fluorescent protein exchange.  

PubMed

We have developed a versatile new class of genetically encoded fluorescent biosensor based on reversible exchange of the heterodimeric partners of green and red dimerization-dependent fluorescent proteins. We demonstrate the use of this strategy to construct both intermolecular and intramolecular ratiometric biosensors for qualitative imaging of caspase activity, Ca(2+) concentration dynamics and other second-messenger signaling activities. PMID:25622108

Ding, Yidan; Li, Jiao; Enterina, Jhon Ralph; Shen, Yi; Zhang, Issan; Tewson, Paul H; Mo, Gary C H; Zhang, Jin; Quinn, Anne Marie; Hughes, Thomas E; Maysinger, Dusica; Alford, Spencer C; Zhang, Yan; Campbell, Robert E

2015-03-01

52

Disposable nitrate-selective optical sensor based on fluorescent dye  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

53

Mosaic-Detector-Based Fluorescence Spectral Imager  

NASA Technical Reports Server (NTRS)

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

Son, Kyung-Ah; Moon, Jeong

2007-01-01

54

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

55

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

PubMed

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

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

2015-01-21

56

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

PubMed

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

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

2015-03-01

57

A fluorescence resonance energy transfer-based method for histone methyltransferases.  

PubMed

A simple dye-quencher fluorescence resonance energy transfer (FRET)-based assay for methyltransferases was developed and used to determine kinetic parameters and inhibitory activity at EHMT1 and EHMT2. Peptides mimicking the truncated histone H3 tail were functionalized in each end with a dye and a quencher, respectively. When lysine-9 residues in the peptides were methylated, they were protected from cleavage by endoproteinase-EndoLysC, whereas unmethylated peptides were cleaved, resulting in an increase in fluorescent intensity. PMID:25703602

Devkota, Kanchan; Lohse, Brian; Jakobsen, Camilla Nyby; Berthelsen, Jens; Clausen, Rasmus Prætorius

2015-05-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

59

Towards a spectrum-based bar code for identification of weakly fluorescent microparticles  

NASA Astrophysics Data System (ADS)

Spectrally resolved detection of fluorescent probes can be used to identify multiple labeled target molecules in an unknown mixture. We study how the spectral shape, the experimental noise, and the number of spectral detection channels affect the success of identification of weakly fluorescent beads on basis of their emission spectra. The proposed formalism allows to estimate the performance of the spectral identification procedure with a given set of spectral codes on the basis of the reference spectra only. We constructed a simple prism-based setup for spectral detection and demonstrate that seven distinct but overlapping spectral codes realized by combining up to three fluorescent dyes bound to a single bead in a barcode-based manner can be reliably identified. The procedure allows correct identification even in the presence of known autofluorescence background stronger than the actual signal.

Petrášek, Zden?k; Wiedemann, Jens; Schwille, Petra

2014-03-01

60

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

Microsoft Academic Search

A new and simple analytical method using HPLC with fluorescence detection was developed for the simultaneous determination of four lignans (phyllanthin, hypophyllanthin, phyltetralin and niranthin) in Phyllanthus niruri L. plant samples. Optimal separation was achieved with an isocratic mobile phase consisting of acetonitrile–water (55:45 v\\/v). The method recorded limits of detection (S\\/N=5) for phyllanthin at 0.61ng\\/mL, hypophyllanthin at 6.02ng\\/mL, phyltetralin

Vikneswaran Murugaiyah; Kit-Lam Chan

2007-01-01

61

A novel nonenzymatic fluorescent sensor for glucose based on silica nanoparticles doped with europium coordination compound.  

PubMed

Amino-functionalized luminescent silica nanoparticles (LSNPs) doped with the europium(III) mixed complex, Eu(TTA)(3)phen with 2-thenoyltrifluoroacetone (TTA) and 1,10-phenanthroline(phen) were synthesized successfully using an revised Stöber method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR), and fluorescence spectroscopy were performed for characterizing the synthesized nanoparticles. In the presence of glucose, the fluorescence intensity of the amino-functionalized LSNPs was enhanced due to the enhanced fluorescence resonance energy transfer. Based on fluorescence-enhancing effect, a simple and sensitive method for the determination of glucose was proposed. Under the optimized experimental conditions, the enhanced fluorescence intensity ratio (DeltaF/F(0)) was linear with the concentration of glucose (c) in the range of 0.0-180 microg ml(-1) with a detection limit of 0.8 microg ml(-1) (S/N=3). The R.S.D. values were 0.33% and 0.37% at the levels of 22.5 and 100 microg ml(-1), respectively. The proposed method was applied to the determination of glucose in synthetic samples with satisfactory results. The proposed method was also performed to the analysis of blood glucose in human serum samples and the results were in good agreement with clinical data provided by the hospital, which indicates that the method presented here is not only simple, sensitive, but also reliable and suitable for practical applications. PMID:19782214

Gao, Feng; Luo, Fabao; Chen, Xiaoxiao; Yao, Wu; Yin, Jun; Yao, Zhen; Wang, Lun

2009-11-15

62

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

Microsoft Academic Search

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

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

2007-01-01

63

Development of fluorescent lead II sensor based on an anthracene derived chalcone.  

PubMed

A simple anthracene based chalcone as a fluorescent chemosensor 1, capable of detecting Pb(2+) in aqueous media, has been synthesized by the reaction between pyridine 2-carboxaldehyde and 9-acetyl anthracene. The Pb(2+) recognition processes follows a photo induced electron transfer (PET) mechanism and are scarcely influenced by other coexisting metal ions. In addition, determination of lead in a variety of samples was also determined. PMID:25744532

Prabhu, J; Velmurugan, K; Nandhakumar, R

2015-06-01

64

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

65

Motor Oil Classification Based on Time-Resolved Fluorescence  

PubMed Central

A time-resolved fluorescence (TRF) technique is presented for classifying motor oils. The system is constructed with a third harmonic Nd:YAG laser, a spectrometer, and an intensified charge coupled device (ICCD) camera. Steady-state and time-resolved fluorescence (TRF) measurements are reported for several motor oils. It is found that steady-state fluorescence is insufficient to distinguish the motor oil samples. Then contour diagrams of TRF intensities (CDTRFIs) are acquired to serve as unique fingerprints to identify motor oils by using the distinct TRF of motor oils. CDTRFIs are preferable to steady-state fluorescence spectra for classifying different motor oils, making CDTRFIs a particularly choice for the development of fluorescence-based methods for the discrimination and characterization of motor oils. The two-dimensional fluorescence contour diagrams contain more information, not only the changing shapes of the LIF spectra but also the relative intensity. The results indicate that motor oils can be differentiated based on the new proposed method, which provides reliable methods for analyzing and classifying motor oils. PMID:24988439

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

2014-01-01

66

Radioiodine detector based on laser induced fluorescence  

DOEpatents

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

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

1980-01-01

67

Thioamide-Based Fluorescent Protease Sensors  

PubMed Central

Thioamide quenchers can be paired with compact fluorophores to design “turn-on” fluorescent protease substrates. We have used this method to study a variety of serine-, cysteine-, carboxyl-, and metallo-proteases, including trypsin, chymotrypsin, pepsin, thermolysin, papain, and calpain. Since thioamides quench some fluorophores red-shifted from those naturally occurring in proteins, this technique can be used for real time monitoring of protease activity in crude preparations of virtually any protease. We demonstrate the value of this method in three model applications: (1) characterization of papain enzyme kinetics using rapid-mixing experiments, (2) selective monitoring of cleavage at a single site in a peptide with multiple proteolytic sites, and (3) analysis of the specificity of an inhibitor of calpain in cell lysates. PMID:24472041

2015-01-01

68

Doped semiconductor nanocrystal based fluorescent cellular imaging probes  

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information available: Characterization details of coating and functionalisation of doped nanocrystals, property of functionalized nanocrystals, quantification of cell labeling and control labeling experiments. See DOI: 10.1039/c3nr00549f

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

2013-05-01

69

Visual and fluorescent detection of acetamiprid based on the inner filter effect of gold nanoparticles on ratiometric fluorescence quantum dots.  

PubMed

In this work, we develop a simple and rapid sensing method for the visual and fluorescent detection of acetamiprid (AC) based on the inner-filter effect (IFE) of gold nanoparticles (AuNPs) on ratiometric fluorescent quantum dots (RF-QDs). The RF-QDs based dual-emission nanosensor was fabricated by assembling green emissive QDs (QDs539nm, ?em=539 nm) on the surface of red emissive QDs (QDs661nm, ?em=661 nm)-doped silica microspheres. The photoluminescence (PL) intensity of RF-QDs could be quenched by AuNPs based on IFE. Acetamiprid can adsorb on the surface of AuNPs due to its cyano group that has good affinity with gold, which could induce the aggregation of AuNPs accompanying color change from red to blue. Thus, the IFE of AuNPs on RF-QDs was weakened and the PL intensity of RF-QDs was recovered accordingly. Under the optimized conditions, the PL intensity of the RF-QDs/AuNPs system was proportional to the concentration of AC in the range of 0.025-5.0 ?g mL(-1), with a detection limit of 16.8 ?g L(-1). The established method had been used for AC detection in environmental and agricultural samples with satisfactory results. PMID:25441897

Yan, Xu; Li, Hongxia; Li, Yang; Su, Xingguang

2014-12-10

70

A Simple Fluid Solver based on the FFT Alias wavefront  

E-print Network

A Simple Fluid Solver based on the FFT Jos Stam Alias wavefront 1218 Third Ave, 8th Floor, Seattle, WA 98101 Abstract This paper presents a very simple implementation of a fluid solver. Our solver is consistent with the equations of fluid flow and produces velocity fields that contain incompressible

Toronto, University of

71

Luminol as a fluorescent acid-base indicator.  

PubMed

The acid and base dissociation constants of luminol are determined at various ionic strengths. The transition interval occurs at pH 7.7-9.0, therefore luminol is a fluorescent indicator for the titration of strong and weak acids and strong bases. Its value as an indicator is established by titrating milk, red wine and cherry juice. PMID:18959899

Erdey, L; Buzás, I; Vigh, K

1966-03-01

72

mb-FLIM: model-based fluorescence lifetime imaging  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

73

A Simple DNA-Based Translation System  

PubMed Central

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

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

2008-01-01

74

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

PubMed

4,5-Bis(hydroxymethyl) acridine (sensor 1) has been discovered and synthesized as a simple-structured Pd(2+) fluorescent probe. Sensor 1 showed highly selective recognition toward Pd(2+) over other examined metal ions in aqueous solution. Under the optimized condition, fluorescence intensity was linearly proportional to the concentration of Pd(2+) in the 0-1 ?M concentration range with detection limits of 0.021 ?M. The EDTA-adding and stoichiometry experiments indicated that sensor 1 was a reversible chemosensor for Pd(2+) with a 2:1 ligand/metal complex at neutral pH. Moreover, the sensor 1 was also successfully applied to determination of Pd(2+) in water samples and palladium-containing catalyst, which made it attractive for sensing applications. PMID:25194318

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

2015-02-25

75

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

76

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

77

Unexpected Complex Formation between Coralyne and Cyclic Diadenosine Monophosphate Providing a Simple Fluorescent Turn-on Assay to Detect This Bacterial Second Messenger  

PubMed Central

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

2015-01-01

78

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

79

Development of microfluidic-based assays to estimate the binding between osteocalcin (BGLAP) and fluorescent antibodies.  

PubMed

Osteocalcin (bone gamma-carboxyglutamate protein; BGLAP) is a highly conserved molecule associated with mineralization of bone matrix. It regulates the dynamics of new bone formation and bone resorption. The synthesis of osteocalcin by osteoblasts is regulated by the active form of vitamin D. In this paper, we report the use of two fluorescent-based assays, one bead-based and a second involving an amino-silane surface pre-treatment, to obtain binding constants of 3.53×10(6) M(-1) and 3.19×10(6) M(-1), respectively, for the binding of BGLAP to fluorescently labeled monoclonal-anti BGLAP-clone 2D5. These simple microfluidic techniques demonstrate the feasibility of developing microsphere-based and surface electrostatically-attached binding assays to study peptide-antibody interactions. Both techniques utilize sub-microliter volumes of material an important consideration when studying bone turnover markers (BTMs) like BGLAP. PMID:25476363

Carmona, Hector; Valadez, Hector; Yun, Yeoheung; Sankar, Jagannathan; Estala, Lissette; Gomez, Frank A

2015-01-01

80

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

PubMed

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

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

2014-11-21

81

Detection of residual concentration of imidazoline inhibitors in oilfield production water based on fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

Fluorescence spectroscopy is applied to detect the residual concentration of imidazoline inhibitors in this study. Imidazoline inhibitors emit a weak fluorescence spectrum at 445 nm excitation wavelength, the addition of eosin Y can enhance the fluorescence intensity obviously and the excitation wavelength is located at 521 nm. The fluorescence intensity has a good linear relationship with the inhibitor concentration. The common ions in oilfield production water do not affect imidazoline detection using eosin Y as fluorescence agent based on fluorescence spectroscopy.

Chen, Zhenyu; Guo, Xianxian; Qiu, Yubing; Guo, Xingpeng

2012-09-01

82

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

83

A microcontroller-based emergency ballast for fluorescent lamps  

Microsoft Academic Search

This paper presents a new emergency ballast for fluorescent lamps. The fundamental block is the microcontroller-based control circuit, which performs the supervision and control function. High-frequency electronics techniques are proposed for the high power factor battery charger and the lamp driver, which provides high luminous efficacy. In this way, size and weight have been minimized for the whole system. With

J. Marcos Alonso; Pedro J. Villegas; J. Diaz; C. Blanco; M. Rico

1997-01-01

84

Basic Dose Response of Fluorescent Screen -based Potal Imaging Device  

Microsoft Academic Search

Purpose : The purpose of this study is to investigate fundamental aspects of the dose response of fluorescent screen-based electronic portal imaging devices (EPIDs). Materials and Methods : We acquired scanned signal across portal planes as we varied the radiation that entered the EPID by changing the thickness and anatomy of the phantom as well as the air gap between

Inhwan J. Yeo; Yonas Yohannes; Yunping Zhu; Sung Kyun

85

Magnetite nanoparticles for biosensor model based on bacteria fluorescence  

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

86

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

PubMed

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

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

2013-12-15

87

Knowledge-Based Vision and Simple Visual Machines  

Microsoft Academic Search

The vast majority of work in machine vision emphasizes the representation of perceived objects and events: it is these internal representations that incorporate the 'knowledge' in knowledge-based vision or form the 'models' in model-based vision. In this paper, we discuss simple machine vision systems developed by artificial evolution rather than traditional engineering design techniques, and note that the task of

Dave Cliff; Jason Noble

1997-01-01

88

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

PubMed

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

Feng, Tingting; Ma, Huimin

2013-04-21

89

Highly selective and sensitive detection of mercuric ion based on a visual fluorescence method.  

PubMed

The instant and on-site detection of trace aqueous mercuric ion still remains a challenge for environmental monitoring and protection. This work demonstrates a new analytical method and its utility for visual detection of aqueous Hg(2+) on the basis of a novel water-soluble CdSe-ZnS quantum dots (QDs) functionalized with a bidentate ligand of 2-hydroxyethyldithiocarbamate (HDTC). The fluorescence of the aqueous HDTC modified QDs (HDTC-QDs) could be selectively and efficiently quenched by Hg(2+) through a surface chelating reaction between HDTC and Hg(2+), and the detection limit was measured to be 1 ppb. Most interestingly, the orange fluorescence of the HDTC-QDs gradually changes to red upon the increasing amount of Hg(2+) added besides the decreasing of the fluorescence intensity. By taking advantage of this optical phenomenon, a paper-based sensor for aqueous Hg(2+) detection has been developed by immobilizing the HDTC-QDs on cellulose acetate paper which has low background fluorescence in the wavelength range. The paper-based sensor showed high sensitivity and selectivity for Hg(2+) visual detection. When Hg(2+) was dropped onto the paper-sensor, an obviously distinguishable fluorescence color evolution (from orange to red) could be clearly observed depending on the concentration of Hg(2+). The limit of detection of the visual method for aqueous Hg(2+) detection was as low as 0.2 ppm. The very simple and effective strategy reported here should facilitate the development of portable and reliable fluorescence chemosensors for mercuric pollution control. PMID:23121315

Yuan, Chao; Zhang, Kui; Zhang, Zhongping; Wang, Suhua

2012-11-20

90

Colorful Protein-Based Fluorescent Probes for Collagen Imaging  

PubMed Central

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

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

2014-01-01

91

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

ERIC Educational Resources Information Center

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

Grayson, Scott M.

2012-01-01

92

A Simple Rule-Based Part of Speech Tagger  

Microsoft Academic Search

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

Eric Brill

1992-01-01

93

Immunosensor systems with the Langmuir-film-based fluorescence detection  

SciTech Connect

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

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

2003-09-30

94

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

95

From fluorescence polarization to Quenchbody: Recent progress in fluorescent reagentless biosensors based on antibody and other binding proteins.  

PubMed

Recently, antibody-based fluorescent biosensors are receiving considerable attention as a suitable biomolecule for diagnostics, namely, homogeneous immunoassay and also as an imaging probe. To date, several strategies for "reagentless biosensors" based on antibodies and natural and engineered binding proteins have been described. In this review, several approaches are introduced including a recently described fluorescent antibody-based biosensor Quenchbody, which works on the principle of fluorescence quenching of attached dye and its antigen-dependent release. The merits and possible demerits of each approach are discussed. This article is part of a Special Issue entitled: Recent advances in molecular engineering of antibody. PMID:24931832

Ueda, Hiroshi; Dong, Jinhua

2014-11-01

96

Two new rhodamine-based fluorescent chemosensors for Fe3+ 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 (CH3OH-H2O = 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. PMID:24700778

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

2014-11-01

97

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

PubMed

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

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

2015-03-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

99

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

100

A Simple Inquiry-Based Lab for Teaching Osmosis  

ERIC Educational Resources Information Center

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

Taylor, John R.

2014-01-01

101

A Simple E-learning System based on Classroom Competition  

E-print Network

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

Cantador, Iván

102

A label-free, fluorescence based assay for microarray  

NASA Astrophysics Data System (ADS)

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

Niu, Sanjun

103

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

104

Highly sensitive fluorescence and SERS detection of azide through a simple click reaction of 8-chloroquinoline and phenylacetylene.  

PubMed

In 0.19 mol/L acetic acid (HAc), a click reaction of 8-chloroquinoline/azide/phenylacetylene take places in aqueous solution without Cu(I) as a catalyst. 8-Chloroquinoline (CQN) exhibited a strong fluorescence peak at 430 nm that was quenched linearly as the concentration of azide increased from 20 to 1000 ng/mL. This quenching was due to consumption of CQN in the click reaction and a decrease in the number of efficiently excited photons due to the presence of triazole-quinoline ramification molecules with strong hydrophobicity. Using blue nanosilver sol as the substrate, CQN absorbed onto the surface of nanosilver particles, showing a strong surface-enhanced Raman scattering (SERS) peak at 1585 cm(-1) that decreased linearly as the azide concentration increased from 8 to 500 ng/mL; the detection limit was 4 ng/mL. Thus, two new, simple and sensitive fluorescence and SERS methods have been developed for the determination of azide via the click reaction. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25045121

Zeng, Qing; Ye, Lingling; Ma, Lu; Yin, Wenqing; Li, Tingsheng; Liang, Aihui; Jiang, Zhiliang

2015-05-01

105

A straightforward immunoassay applicable to a wide range of antibodies based on surface enhanced fluorescence.  

PubMed

A straightforward immunoassay based on surface enhanced fluorescence (SEF) has been demonstrated using a fluorescent immune substrate and antibody functionalized-silver nanoparticles. Unlike the conventional SEF-based immunoassay, which usually uses the dye-labeled antibodies and the metallic nanostructured-substrates, the presented immune system does not need the antibodies to be labeled with dye molecules. Thus, this immunoassay can be easily applied to the detection of a wide range of target antigens, which is of great importance for its practical application. The experimental results show that this immunoassay has a good specificity as well as the capacity of quantitative detection. Basically, the surface density of the immuno-adsorbed silver nanoparticles increases with the increased amount of target antigens, resulting in a fluorescence enhancement up to around 7 fold. The dose-responsive performance of the immunoassay has been investigated and the limit of detection (LOD) is 1 ng/mL. Due to its simple preparation method and the wide range of detectable antigens, this presented immunoassay is expected to be helpful for extending the SEF-based application. PMID:23463294

Zhang, Ruohu; Wang, Zhuyuan; Song, Chunyuan; Yang, Jing; Cui, Yiping

2013-05-01

106

Phthalocyanine dimerization-based molecular beacons using near-IR fluorescence  

PubMed Central

Herein we demonstrate the use of a novel dimerization-based molecular beacon (MB) probe consisting of two metallo-phthalocyanine (Pc) fluorophores that use near-IR fluorescence, appropriate for highly specific and sensitive in-vivo and/or in-vitro DNA/RNA detection. Pc’s possess a propensity to form non-fluorescent H-dimers that is utilized as the molecular “off” switch in the closed MB conformation. The “on” switch, which is generated when the solution target binds to the loop of the MB forming the open form, also provides two fluorophores for transduction resulting in a doubling of the extinction coefficient and improving the resulting fluorescence yield compared to a classical single-fluorophore/quencher MB system. In addition, the Pc-based MBs possess high thermal, photo and chemical stabilities that are essential for many highly sensitive applications, such as molecular imaging. The dimer-based MBs were obtained using a simple single-step synthesis procedure and demonstrated excellent quenching efficiencies (98%) as well as a high signal-to-background ratio (~60) exceeding the performance characteristics of many conventionally-available MB probes. PMID:19191492

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

2009-01-01

107

Modulating Fluorescence Anisotropy of Terminally Labeled Double-Stranded DNA via the Interaction between Dye and Nucleotides for Rational Design of DNA Recognition Based Applications.  

PubMed

Effective signal enhancement for fluorescence anisotropy in a simple manner is most desirable for fluorescence anisotropy method development. This work aimed to provide insights into the fluorescence anisotropy of terminally labeled double-stranded DNA (dsDNA) to facilitate a facile and universal design strategy for DNA recognition based applications. We demonstrated that fluorescence anisotropy of dsDNA could be regulated by the nature of dyes, the molecular volume, and the end structure of dsDNA. Fluorescence anisotropy ascended with the increased number of base pairs up to 18 bp and leveled off thereafter, indicating the molecular volume was not the only factor responsible for fluorescence anisotropy. By choosing dyes with the positively charged center, high fluorescence anisotropy signal was obtained due to the confinement of the segmental motion of dyes through the electrostatic interaction. By properly designing the end structure of dsDNA, fluorescence anisotropy could be further improved by enlarging the effective overall rotational volume, as supported by two-dimensional (2D) (1)H-(1)H nuclear Overhauser enhancement spectroscopy (NOESY). With the successful enhancement of the fluorescence anisotropy for terminally labeled dsDNA, simple and universal designs were demonstrated by sensing of major classes of analytes from macromolecules (DNA and protein) to small molecules (cocaine). PMID:25671552

Huang, Hongduan; Wei, Hejia; Zou, Mingjian; Xu, Xiao; Xia, Bin; Liu, Feng; Li, Na

2015-03-01

108

Smartphone-based fluorescence detector for mHealth.  

PubMed

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

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

2015-01-01

109

Highly efficient blue electroluminescence based on thermally activated delayed fluorescence  

NASA Astrophysics Data System (ADS)

Organic compounds that exhibit highly efficient, stable blue emission are required to realize inexpensive organic light-emitting diodes for future displays and lighting applications. Here, we define the design rules for increasing the electroluminescence efficiency of blue-emitting organic molecules that exhibit thermally activated delayed fluorescence. We show that a large delocalization of the highest occupied molecular orbital and lowest unoccupied molecular orbital in these charge-transfer compounds enhances the rate of radiative decay considerably by inducing a large oscillator strength even when there is a small overlap between the two wavefunctions. A compound based on our design principles exhibited a high rate of fluorescence decay and efficient up-conversion of triplet excitons into singlet excited states, leading to both photoluminescence and internal electroluminescence quantum yields of nearly 100%.

Hirata, Shuzo; Sakai, Yumi; Masui, Kensuke; Tanaka, Hiroyuki; Lee, Sae Youn; Nomura, Hiroko; Nakamura, Nozomi; Yasumatsu, Mao; Nakanotani, Hajime; Zhang, Qisheng; Shizu, Katsuyuki; Miyazaki, Hiroshi; Adachi, Chihaya

2015-03-01

110

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

111

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

112

Detection of botulinum toxins: micromechanical and fluorescence-based sensors.  

PubMed

Botulinum neurotoxins (BoNTs) are the most lethal of known human toxins, exerting their actions by cleaving the soluble N-ethyl maleimide-sensitive fusion protein attachment protein receptors (SNAREs) required for neurotransmitter release. Early detection of these toxins is important for appropriate medical treatment. To detect BoNT activity, traditional assays monitor the effects of the toxins on a mammalian organism (observing signs of botulism in mice), or identify cleaved substrate molecules (electrophoresis and immunoblot). Similarly, enzyme-linked assays were used for screening potential toxin inhibitors in vitro in attempt to select antitoxins that could be used for therapeutic purposes. Here we review two recently developed sensor systems for detection of toxin activity in vitro and in living cells. In vitro detection was carried out using a micromechanosensor that relies on the attachment of a bead to the micromachined cantilever through the interactions between SNARE proteins, with synaptobrevin 2 deposited onto beads and syntaxin 1A deposited onto cantilevers. The presence of toxin is indicated by the detachment of the bead, resulting from cleavage of synaptobrevin 2. Additional in vitro detection is possible using fluorescent sensors constructed by inserting linkers, containing fragments of SNARE proteins acting as toxin substrates, between cyan and yellow fluorescent proteins (CFP and YFP). Toxins cause the cleavage of these linkers and thereby abolish fluorescence resonance energy transfer (FRET) between CFP and YFP. This approach, combined with an additional sensor based on subcellular redistribution of YFP fluorescence in cells, was used for cell-based screening of toxin activity. PMID:16100750

Parpura, Vladimir; Chapman, Edwin R

2005-08-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

114

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

PubMed

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

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

2015-02-01

115

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.

116

Data storage based on photochromic and photoconvertible fluorescent proteins.  

PubMed

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

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

2010-09-15

117

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

118

Fluorescent nanosensor for probing histone acetyltransferase activity based on acetylation protection and magnetic graphitic nanocapsules.  

PubMed

Protein acetylation catalyzed by histone acetyltransferases (HATs) is significant in biochemistry and pharmacology because of its crucial role in epigenetic gene regulations. Herein, an antibody-free fluorescent nanosensor is developed for the facile detection of HAT activity based on acetylation protection against exopeptidase cleavage and super-quenching ability of nanomaterials. It is shown for the first time that HAT-catalyzed acetylation could protect the peptide against exopeptidase digestion. FITC-tagged acetylated peptide causes the formation of a nano-quenchers/peptide nano-complex resulting in fluorescence quenching, while the unacetylated peptide is fully degraded by exopeptidase to release the fluorophore and restore fluorescence. Four kinds of nano-quenchers, including core-shell magnetic graphitic nanocapsules (MGN), graphene oxide (GO), single-walled carbon nanotubes (SWCNTs), and gold nanoparticles (AuNPs), are comprehensively compared. MGN shows the best selectivity to recognize the acetylated peptide and the lowest detection limit because of its excellent quenching efficiency and magnetic enrichment property. With this MGN-based nanosensor, HAT p300 is detected down to 0.1 nM with wide linear range from 0.5 to 100 nM. This sensor is feasible to assess HAT inhibition and detect p300 activity in cell lysate. The proposed nanosensor is simple, sensitive, and cost-effective for HAT assay, presenting a promising toolkit for epigenetic research and HAT-targeted drug discovery. PMID:25277402

Han, Yitao; Li, Pei; Xu, Yiting; Li, Hao; Song, Zhiling; Nie, Zhou; Chen, Zhuo; Yao, Shouzhuo

2015-02-01

119

Fluorescence-based detection of single-nucleotide changes in RNA using graphene oxide and DNAzyme.  

PubMed

We report a simple fluorometric method for detection of single-nucleotide changes in RNA using graphene oxide (GO) and RNA-cleaving DNAzyme. The fluorescent DNA probe (F-DNA) was annealed to RNA fragments generated by RNA cleavage with DNAzyme specific to mutant RNA. The F-DNA-RNA duplex attenuated the quenching of F-DNA fluorescence by GO. PMID:25714982

Hong, Chaesun; Kim, Dong-Min; Baek, Ahruem; Chung, Hyewon; Jung, Woong; Kim, Dong-Eun

2015-03-17

120

Photon upconversion in homogeneous fluorescence-based bioanalytical assays.  

PubMed

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

Soukka, Tero; Rantanen, Terhi; Kuningas, Katri

2008-01-01

121

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

NASA Astrophysics Data System (ADS)

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

Jukl, Jennifer Marie

122

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

123

Hybrid Integrated Silicon Microfluidic Platform for Fluorescence Based Biodetection  

PubMed Central

The desideratum to develop a fully integrated Lab-on-a-chip device capable of rapid specimen detection for high throughput in-situ biomedical diagnoses and Point-of-Care testing applications has called for the integration of some of the novel technologies such as the microfluidics, microphotonics, immunoproteomics and Micro Electro Mechanical Systems (MEMS). In the present work, a silicon based microfluidic device has been developed for carrying out fluorescence based immunoassay. By hybrid attachment of the microfluidic device with a Spectrometer-on-chip, the feasibility of synthesizing an integrated Lab-on-a-chip type device for fluorescence based biosensing has been demonstrated. Biodetection using the microfluidic device has been carried out using antigen sheep IgG and Alexafluor-647 tagged antibody particles and the experimental results prove that silicon is a compatible material for the present application given the various advantages it offers such as cost-effectiveness, ease of bulk microfabrication, superior surface affinity to biomolecules, ease of disposability of the device etc., and is thus suitable for fabricating Lab-on-a-chip type devices.

Chandrasekaran, Arvind; Acharya, Ashwin; You, Jian Liang; Soo, Kim Young; Packirisamy, Muthukumaran; Stiharu, Ion; Darveau, Andre

2007-01-01

124

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

PubMed

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

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

2014-06-01

125

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

PubMed

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

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

2012-05-21

126

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

PubMed Central

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

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

2014-01-01

127

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

PubMed Central

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

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

2010-01-01

128

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

129

Monitoring water supplies for weaponized bacteria and bacterial toxins using rapid fluorescence-based viability and affinity assays  

NASA Astrophysics Data System (ADS)

The rapid detection of weaponized bacteria and toxins is a major problem during a biological attack. Although sensitive detection formats exist for many biowarfare agents, they often require advanced training and complex procedures. Luna has developed simple, rapid means for determining the presence of pathogens and bacterial toxins in water supplies using fluorescence-based assays that can be adapted for field use. The batteries of rapid assays are designed for i) determining cell viability and bacterial loads by exploiting metabolic markers (e.g., acid-production, redox potentials, etc) and ii) detecting bacterial toxins using fluorescent, polymerized affinity liposomes (fluorosomes). The viability assays were characterized using E. coli, S. aureus and the anthrax simulant, B. globigii. The viability assays detected bacterial loads of ~ 104 CFU/ml and with simple filtration ~ 100CFU/ml could be detected. The affinity fluorosomes were characterized using cholera toxin (CT). Affinity liposomes displaying GM1 and anti-CT antibodies could detect CT at fluorescence system, Luna characterized the binding of affinity fluorosomes to respective targets and determined the responses of bacterial loads in the fluorescent viability assays. Using this two-tiered approach, Luna demonstrated that water susceptible to sabotage could be easily monitored and confirmed for specific agents using simple, general and specific fluorescence-based detection schemes based on metabolism and ligand-target interactions.

Van Tassell, Roger L.; Evans, Mishell

2004-03-01

130

Rapid fluorescence-based measurement of toxicity in anaerobic digestion.  

PubMed

A rapid fluorescence measurement based on resazurin reduction was developed and applied for the detection of toxicants/inhibitors to anaerobic digestion metabolism. By initially using a pure facultative anaerobic strain, Enterococcus faecalis as a model organism, this technique proved to be fast and sensitive when detecting the model toxicant, pentachlorophenol (PCP). The technique revealed significant metabolic changes in Enterococcus faecalis with a PCP spike ranging from 0.05 to 100 mg/L, and could detect PCP's toxicity to E. faecalis at a concentration of only 0.05 mg/L in 8 min. Furthermore, by extending this technique to a mixed anaerobic sludge, not only could the effect of 0.05-100 mg/L PCP be determined on anaerobic digestion metabolism within 10 min, but also its rate of biogas production. These results suggest that a resazurin-based fluorescence measurement can potentially be incorporated into a microfluidic system to develop a biosensor for the real-time monitoring, control and early warning of toxicant/inhibitor loads in the influent to an anaerobic digestion system. PMID:25768985

Chen, Jian Lin; Ortiz, Raphael; Xiao, Yeyuan; Steele, Terry W J; Stuckey, David C

2015-05-15

131

Organic liquids-responsive ?-cyclodextrin-functionalized graphene-based fluorescence probe: label-free selective detection of tetrahydrofuran.  

PubMed

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

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

2014-01-01

132

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

133

[Simple analytical method of bromine in fruits and grain products with wavelength dispersive X-ray fluorescence spectrometer].  

PubMed

A simple analytical method was developed for the determination of total bromine in fruits and grain products by means of wavelength dispersive X-ray fluorescence spectrometry (WDXRF).Five gram samples of fresh fruits, frozen fruits, dried fruits and grain products were extracted with distilled water twice and diluted to 25 mL with distilled water. The sample solution (0.5 mL) was dripped onto the filter paper, which was dried and analyzed by WDXRF. The working curve was linear in the range of 0 to 10 microg/mL. Recoveries at the level of 5 microg/g were 76-104%. The detection limit was 0.5 microg/g and the determination limit was 1.5 microg/g in foods. Compared to the GC-ECD method, this method gave equivalent results for fresh fruits, frozen fruits and grain products. In addition, some dried fruits, in which a slightly high level was detected, gave almost the same results with the GC-ECD method. Therefore, this method is considered to be available as an alternative to the GC-ECD method. PMID:20453454

Tateishi, Yukinari; Hashimoto, Tsuneo; Ushiyama, Keiko; Sakai, Naoko; Baba, Itoko; Nagayama, Toshihiro

2010-01-01

134

A distributed fiber optic sensor based on cladding fluorescence  

Microsoft Academic Search

The fiber for the sensor is formed by cladding fused silica during drawing with polydimethyl siloxane into which an organic fluorescent dye, 9, 10-diphenylanthracene, has been dissolved. Upon side illumination at a wavelength within the excitation range of the dye, the cladding fluoresces; some of this fluorescence is coupled into guided modes in the fiber core through the evanescent fields

ROBERT A. LIEBERMAN; L. L. Blyler; LEONARD G. COHEN

1990-01-01

135

Glycol Chitosan-Based Fluorescent Theranostic Nanoagents for Cancer Therapy  

PubMed Central

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

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

2014-01-01

136

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

137

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

138

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

PubMed Central

A fluorescent molecularly imprinted nanosensor was obtained by grafting imprinted polymer onto the surface of multi-wall carbon nanotubes and post-imprinting treatment with fluorescein isothiocyanate (FITC). The fluorescence of lysozyme-imprinted polymer (Lys-MIP) was quenched more strongly by Lys than that of nonimprinted polymer (NIP), which indicated that the Lys-MIP could recognize Lys. The resulted imprinted material has the ability to selectively sense a target protein, and an imprinting factor of 3.34 was achieved. The Lys-MIP also showed selective detection for Lys among other proteins such as cytochrome C (Cyt C), hemoglobin (HB) and bovine serum albumin (BSA) due to the imprinted sites in the Lys-MIP. This approach combines the high selectivity of surface molecular imprinting technology and fluorescence, and converts binding events into detectable signals by monitoring fluorescence spectra. Therefore, it will have further applications for Lys sensing. PMID:24077318

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

2013-01-01

139

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

140

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

141

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

142

Coumarin-based fluorescent probes for H2S detection.  

PubMed

Although hydrogen sulfide (H(2)S) has been known as a toxic gas with unpleasant rotten egg smell, the correlation between H(2)S and physiological processes has attracted scientists to develop brand new methods to monitor such a gaseous molecule in vitro and in vivo. Herein, we described a couple of coumarin-based fluorescent probes (1a and 1b) that can be activated by reduction of azide to amine in the presence of H(2)S. It should be emphasized that probe 1b demonstrated high selectivity and sensitivity for H(2)S over other relevant reactive sulfur species in vitro, as well as identified exogenous H(2)S in living cells. PMID:23001475

Li, Wenhua; Sun, Wei; Yu, Xiaoqiang; Du, Lupei; Li, Minyong

2013-01-01

143

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

PubMed

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

Murugaiyah, Vikneswaran; Chan, Kit-Lam

2007-06-22

144

Latest methods of fluorescence-based protein crystal identification  

PubMed Central

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

Meyer, Arne; Betzel, Christian; Pusey, Marc

2015-01-01

145

A simple microviscometric approach based on Brownian motion tracking.  

PubMed

Viscosity-an integral property of a liquid-is traditionally determined by mechanical instruments. The most pronounced disadvantage of such an approach is the requirement of a large sample volume, which poses a serious obstacle, particularly in biology and biophysics when working with limited samples. Scaling down the required volume by means of microviscometry based on tracking the Brownian motion of particles can provide a reasonable alternative. In this paper, we report a simple microviscometric approach which can be conducted with common laboratory equipment. The core of this approach consists in a freely available standalone script to process particle trajectory data based on a Newtonian model. In our study, this setup allowed the sample to be scaled down to 10 ?l. The utility of the approach was demonstrated using model solutions of glycerine, hyaluronate, and mouse blood plasma. Therefore, this microviscometric approach based on a newly developed freely available script can be suggested for determination of the viscosity of small biological samples (e.g., body fluids). PMID:25725855

Hnyluchová, Zuzana; Bjalon?íková, Petra; Karas, Pavel; Mravec, Filip; Halasová, Tereza; Peka?, Miloslav; Kubala, Lukáš; Víte?ek, Jan

2015-02-01

146

A simple microviscometric approach based on Brownian motion tracking  

NASA Astrophysics Data System (ADS)

Viscosity—an integral property of a liquid—is traditionally determined by mechanical instruments. The most pronounced disadvantage of such an approach is the requirement of a large sample volume, which poses a serious obstacle, particularly in biology and biophysics when working with limited samples. Scaling down the required volume by means of microviscometry based on tracking the Brownian motion of particles can provide a reasonable alternative. In this paper, we report a simple microviscometric approach which can be conducted with common laboratory equipment. The core of this approach consists in a freely available standalone script to process particle trajectory data based on a Newtonian model. In our study, this setup allowed the sample to be scaled down to 10 ?l. The utility of the approach was demonstrated using model solutions of glycerine, hyaluronate, and mouse blood plasma. Therefore, this microviscometric approach based on a newly developed freely available script can be suggested for determination of the viscosity of small biological samples (e.g., body fluids).

Hnyluchová, Zuzana; Bjalon?íková, Petra; Karas, Pavel; Mravec, Filip; Halasová, Tereza; Peka?, Miloslav; Kubala, Lukáš; Víte?ek, Jan

2015-02-01

147

Synthesis of a new fluorescent macrocyclic [alpha]-amino acid derivative via tandem cross-enyne\\/ring-closing metathesis cascade catalyzed by ruthenium based catalysts  

Microsoft Academic Search

A simple methodology to a unique macrocyclic ?-amino acid (AAA) derivative involving three step synthetic sequence has been reported. In addition, various ruthenium based catalysts were studied to enhance the selectivity of the desired macrocyclic AAA derivative 6. The fluorescence behavior of these AAA derivatives 5 and 6 indicate their potential applications in biological sciences as biomarkers, ion sensors and

Sambasivarao Kotha; Deepti Bansal; Kuldeep Singh; Subhasree Banerjee

2011-01-01

148

Ultrasensitive and fast fluorescent bioassay based on fluorescence enhancement of silver nanoparticles.  

PubMed

An ultrasensitive, fast and specific fluorescent platform for protein detection is developed. In this protocol, silver nanoparticles were conjugated with paramagnetic particles (MPs-Ag) for target capture, concentration and separation; fluorescent dyes functionalized silver nanoparticles (Tag) for generating signals. The presented method is highly sensitive and specific with a detection limit of 2.2 pM for thrombin, and no significant interference was observed for other proteins such as human serum albumin (HSA), lysozyme and IgG. This novel approach combining the magnetic separation and concentration of MPs-Ag, aptamer recognition and fluorescence enhancement of Tag, can be successfully used to enhance the sensitivity of detecting ultra-low levels of target proteins or biomolecules. PMID:24165800

Li, Hui; Qiang, Weibing; Wang, Chongzhi; Vuki, Maika; Xu, Danke

2013-11-12

149

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

150

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

Microsoft Academic Search

A simple, rapid and high-throughput fluorescent polarization immunoassay (FPIA) for simultaneous determination of organophosphorus pesticides (OPs) using a broad-specificity monoclonal antibody was developed. The effects of tracer structure, tracer concentration, antibody dilution, methanol content and matrix effect on FPIA performance were studied. The FPIA can detect 5 OPs simultaneously with a limit of detection below 10ngmL?1. The time required for

Zhen-Lin Xu; Qiang Wang; Hong-Tao Lei; Sergei A. Eremin; Yu-Dong Shen; Hong Wang; Ross C. Beier; Jin-Yi Yang; Ksenia A. Maksimova; Yuan-Ming Sun

151

Analysis of lignans from Phyllanthus niruri L. in plasma using a simple HPLC method with fluorescence detection and its application in a pharmacokinetic study  

Microsoft Academic Search

A simple analytical method using HPLC with fluorescence detection was developed for the simultaneous determination of four lignans, phyllanthin (1), hypophyllanthin (2), phyltetralin (3) and niranthin (4) from Phyllanthus niruri L. in plasma. The method recorded limits of detection for 1, 2, 3 and 4 as 1.22, 6.02, 0.61 and 1.22ng\\/ml, respectively, at a signal-to-noise ratio of 5:1 whereas their

Vikneswaran Murugaiyah; Kit Lam Chan

2007-01-01

152

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

E-print Network

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

Blinov, Boris

153

Sensors and Actuators B 111112 (2005) 230241 Improvements in LED-based fluorescence analysis systems  

E-print Network

Sensors and Actuators B 111­112 (2005) 230­241 Improvements in LED-based fluorescence analysis the stability, power output, and spectral flexibility of light emitting diode (LED)-based systems used to excite fluorescence or other forms of luminescence. LEDs are an attractive alternative to conventional white

Wilson, Denise

154

Prediction of potential drug targets based on simple sequence properties  

PubMed Central

Background During the past decades, research and development in drug discovery have attracted much attention and efforts. However, only 324 drug targets are known for clinical drugs up to now. Identifying potential drug targets is the first step in the process of modern drug discovery for developing novel therapeutic agents. Therefore, the identification and validation of new and effective drug targets are of great value for drug discovery in both academia and pharmaceutical industry. If a protein can be predicted in advance for its potential application as a drug target, the drug discovery process targeting this protein will be greatly speeded up. In the current study, based on the properties of known drug targets, we have developed a sequence-based drug target prediction method for fast identification of novel drug targets. Results Based on simple physicochemical properties extracted from protein sequences of known drug targets, several support vector machine models have been constructed in this study. The best model can distinguish currently known drug targets from non drug targets at an accuracy of 84%. Using this model, potential protein drug targets of human origin from Swiss-Prot were predicted, some of which have already attracted much attention as potential drug targets in pharmaceutical research. Conclusion We have developed a drug target prediction method based solely on protein sequence information without the knowledge of family/domain annotation, or the protein 3D structure. This method can be applied in novel drug target identification and validation, as well as genome scale drug target predictions. PMID:17883836

Li, Qingliang; Lai, Luhua

2007-01-01

155

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

156

Fluorescence microplate-based assay for tumor necrosis factor activity using SYTOX Green stain.  

PubMed

We have developed a simple, sensitive, fluorescence microplate-based assay for tumor necrosis factor (TNF) biological activity. The assay employs SYTOX Green nucleic acid stain to detect TNF-induced cell necrosis in actinomycin D sensitized cultured cell lines. SYTOX Green stain is a cationic unsymmetrical cyanine dye that is excluded from live cells but can readily penetrate cells with compromised cell membranes. Upon binding to cellular nucleic acids, the dye exhibits a large enhancement in fluorescence, which is monitored at fluorescein wavelengths. We detected 2.5 pg/mL and quantitated 25-500 pg/mL recombinant murine (rm) and recombinant human (rh) TNF-alpha, using mouse fibroblast-derived WEHI 164, WEHI 13var, and L929 cell lines. The procedure can also be used to detect agents that modulate TNF activity. We demonstrated complete inhibition of rhTNF-alpha using monoclonal anti-human TNF-alpha antibody and determined that approximately 20 ng/mL antibody was sufficient to neutralize 50% of the biological activity of 250 pg/mL rhTNF-alpha in these cell lines. Reagents are added in a single step, followed by a 6- to 8-h incubation period, during which the cytokine exhibits its effects. There are no wash steps, and the assay is readily amenable to automation and high-throughput screening procedures. PMID:11373072

Jones, L J; Singer, V L

2001-06-01

157

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

158

Fluorescent nanodiamonds for ultrasensitive detection  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

159

Fluorescence diffuse optical tomography: a wavelet-based model reduction  

NASA Astrophysics Data System (ADS)

Fluorescence diffuse optical tomography is becoming a powerful tool for the investigation of molecular events in small animal studies for new therapeutics developments. Here, the stress is put on the mathematical problem of the tomography, that can be formulated in terms of an estimation of physical parameters appearing as a set of Partial Differential Equations (PDEs). The Finite Element Method has been chosen here to resolve the diffusion equation because it has no restriction considering the geometry or the homogeneity of the system. It is nonetheless well-known to be time and memory consuming, mainly because of the large dimensions of the involved matrices. Our principal objective is to reduce the model in order to speed up the model computation. For that, a new method based on a multiresolution technique is chosen. All the matrices appearing in the discretized version of the PDEs are projected onto an orthonormal wavelet basis, and reduced according to the multiresolution method. With the first order resolution, this compression leads to the reduction of a factor 2x2 of the initial dimension, the inversion of the matrices is approximately 4 times faster. A validation study on a phantom was conducted to evaluate the feasibility of this reduction method.

Frassati, Anne; DaSilva, Anabela; Dinten, Jean-Marc; Georges, Didier

2007-07-01

160

A simple enzyme based biosensor on flexible plastic substrate  

NASA Astrophysics Data System (ADS)

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

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

2010-08-01

161

Fluorescence-based test of fiber-optic continuity.  

PubMed

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

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

1997-04-20

162

Fluorescence lifetime-based sensing of sodium by an optode.  

PubMed

We report a 1,2,3-triazol fluoroionophore for detecting Na(+) that shows in vitro enhancement in the Na(+)-induced fluorescence intensity and decay time. The Na(+)-selective molecule 1 was incorporated into a hydrogel as a part of a fiber optical sensor. This sensor allows the direct determination of Na(+) in the range of 1-10 mM by measuring reversible fluorescence decay time changes. PMID:25277847

Schwarze, Thomas; Müller, Holger; Ast, Sandra; Steinbrück, Dörte; Eidner, Sascha; Geissler, Felix; Kumke, Michael U; Holdt, Hans-Jürgen

2014-11-25

163

A facile fluorescence method for versatile biomolecular detection based on pristine ?-Fe2O3 nanoparticle-induced fluorescence quenching.  

PubMed

This work investigated the interactions of ?-Fe2O3 nanoparticles (NPs) with different structural nucleic acids and their fluorescence quenching ability towards fluorophore-labelled nucleic acid probes. Different from bulk ?-Fe2O3 samples, nanoscale ?-Fe2O3 particles exhibit the unique properties of strong adsorption and fluorescence quenching to fluorophore-labelled single-stranded DNA (ssDNA) probes. Based on these findings, a facile fluorescence method was developed for versatile quantification of nucleic acids. The size scale of NPs makes a significant impact on this sensing platform. Better selectivity was given by bigger NP (50-100nm)-based nucleic acid-sensing platform compared with smaller NP (30nm)-based one. In the 50-100nm ?-Fe2O3 NP-based sensing platform, single nucleotide mismatch or single base-pair mismatch can even be effectively discriminated. The targets of micro-RNA (miRNA), ssDNA and double-stranded DNA (dsDNA) are sensitively detected with detection limits of 0.8nM, 1.1nM and 0.64nM (S/N=3), respectively. Significantly, ?-Fe2O3 NPs possess different affinities towards ssDNA probes with different lengths, and can be used as a universal quencher for ssDNA probes labelled with different fluorescent dyes. On the basis of these properties, the pristine ?-Fe2O3 NPs hold the potential to be widely utilized in the development of novel biosensors with signal amplification or simultaneous multiple target detection strategies. PMID:25588703

Song, Chan; Wang, Guan-Yao; Kong, De-Ming

2015-06-15

164

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

PubMed

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

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

2014-05-30

165

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

PubMed Central

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

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

2010-01-01

166

Cytometric sorting based on the fluorescence lifetime of spectrally overlapping signals  

PubMed Central

Flow cytometry is a well-established and powerful high-throughput fluorescence measurement tool that also allows for the sorting and enrichment of subpopulations of cells expressing unique fluorescence signatures. Owing to the reliance on intensity-only signals, flow cytometry sorters cannot easily discriminate between fluorophores that spectrally overlap. In this paper we demonstrate a new method of cell sorting using a fluorescence lifetime-dependent methodology. This approach, referred to herein as phase-filtered cell sorting (PFCS), permits sorting based on the average fluorescence lifetime of a fluorophore by separating fluorescence signals from species that emit differing average fluorescence lifetimes. Using lifetime-dependent hardware, cells and microspheres labeled with fluorophores were sorted with purities up to 90%. PFCS is a practical approach for separating populations of cells that are stained with spectrally overlapping fluorophores or that have interfering autofluorescence signals. PMID:23787669

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

2013-01-01

167

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

PubMed

Fluorescent carbon dots (CD) possess impressive potential in bioimaging because of their low photobleaching, absence of optical blinking and good biocompatibility. However, their relatively short excitation/emission wavelengths restrict their application in in vivo imaging. In the present study, a kind of CD was prepared by a simple heat treatment method using glycine as the only precursor. The diameter of CD was lower than 5 nm, and the highest emission wavelength was 500 nm. However, at 600 nm, there was still a relatively strong fluorescent emission, suggesting CD could be used for in vivo imaging. Additionally, several experiments demonstrated that CD possessed good serum stability and low cytotoxicity. In vitro, CD could be taken up into C6 glioma cells in a time- and concentration-dependent manner, with both endosomes and mitochondria involved. In vivo, CD could be used for non-invasive glioma imaging because of its high accumulation in the glioma site of the brain, which was demonstrated by both in vivo imaging and ex vivo tissue imaging. Furthermore, the fluorescent distribution in tissue slices also showed CD distributed in glioma with high intensity, while with a low intensity in normal brain tissue. In conclusion, CD were prepared using a simple method with relatively long excitation and emission wavelengths and could be used for non-invasive glioma imaging. PMID:25031208

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

2014-09-01

168

Feasibility analysis of an epidermal glucose sensor based on time-resolved fluorescence  

E-print Network

-prick capillary blood sampling, which is painful and prevents detection of abnormal glucose levels while sleeping on fluorescence. Currently, diabetic pa- tients measure their blood glucose concentrations by fingerFeasibility analysis of an epidermal glucose sensor based on time-resolved fluorescence Kamal M

Pilon, Laurent

169

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

170

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

PubMed

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

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

2012-03-11

171

Competitive homogeneous digoxigenin immunoassay based on fluorescence quenching by gold nanoparticles  

Microsoft Academic Search

We report on a competitive, homogeneous immunoassay for the detection of the hapten digoxigenin. The assay is based on competitive fluorescence quenching by gold nanoparticles. Digoxigenin is indirectly labeled with the fluorophore Cy3B through bovine serum albumin and used as a marker. Gold nanoparticles functionalized with anti-digoxigenin antibodies serve as fluorescence quenchers. Free digoxigenin molecules in the analyte solution compete

Sergiy Mayilo; Benjamin Ehlers; Michael Wunderlich; Thomas A. Klar; Hans-Peter Josel; Dieter Heindl; Alfons Nichtl; Konrad Kürzinger; Jochen Feldmann

2009-01-01

172

Shipboard oceanographic fluorescence lidar development and evaluation based on measurements in Antarctic waters  

E-print Network

to derive data on phytoplankton pigments and other substances that are broadly dispersed in the upper water. Attempts have also been made to use time-resolved fluorescence signals for a classification of oil spills, which is based on the fluorescence decay time characteristics of oil. 17,18,19,20 Less effort has been

Oldenburg, Carl von Ossietzky Universität

173

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

174

A VBA-based Simulation for Teaching Simple Linear Regression  

ERIC Educational Resources Information Center

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

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

2004-01-01

175

Fluorescent quenching-based quantitative detection of specific DNA/RNA using a BODIPY® FL-labeled probe or primer  

PubMed Central

We have developed a simple method for the quantitative detection of specific DNA or RNA molecules based on the finding that BODIPY® FL fluorescence was quenched by its interaction with a uniquely positioned guanine. This approach makes use of an oligonucleotide probe or primer containing a BODIPY® FL-modified cytosine at its 5?-end. When such a probe was hybridized with a target DNA, its fluorescence was quenched by the guanine in the target, complementary to the modified cytosine, and the quench rate was proportional to the amount of target DNA. This widely applicable technique will be used directly with larger samples or in conjunction with the polymerase chain reaction to quantify small DNA samples. PMID:11239011

Kurata, Shinya; Kanagawa, Takahiro; Yamada, Kazutaka; Torimura, Masaki; Yokomaku, Toyokazu; Kamagata, Yoichi; Kurane, Ryuichiro

2001-01-01

176

A novel method for non-transferrin-bound iron quantification by chelatable fluorescent beads based on flow cytometry.  

PubMed

The reliable measurement of non-transferrin-bound iron (NTBI) in serum has proved to be difficult and generally time consuming. We have sought a simple and fast method for such a determination. We adopted a fluorescence assay and designed a fluorescent dye with a chelating agent attached to sense iron. To avoid autofluorescence from serum samples, the iron probes were linked to beads and the autofluorescence could be separated and excluded from the measurement by flow cytometry due to the size difference between beads and serum proteins. Fluorescent beads containing both fluorescent and chelating moieties have been synthesized. The nature of the chelating function has been systematically investigated using four different chelators: bidentate hydroxypyranone, bidentate hydroxypyridinone, hexadentate hydroxypyranone and hexadentate hydroxypyridinone, each with different iron affinity constants. Competition studies demonstrate that the hexadentate hydroxypyridinone-based beads are capable of scavenging most of low molecular mass and albumin-bound iron but negligible amounts of iron from transferrin and ferritin. Serum samples from 30 patients with different types of disease and normal volunteers were measured. The concentrations of NTBI fall in the range -0.41 to +6.5 ?M. The data have been compared with those obtained from the traditional 'NTA' method. PMID:25093426

Ma, Yongmin; Podinovskaia, Maria; Evans, Patricia J; Emma, Giovanni; Schaible, Ulrich E; Porter, John; Hider, Robert C

2014-11-01

177

A metal-enhanced fluorescence sensing platform based on new mercapto rhodamine derivatives for reversible Hg(2+) detection.  

PubMed

A new metal-enhanced fluorescence (MEF) chemosensor HMS-Ag-R-2SH for Hg(2+) has been prepared via a simple and effective method. The fluorescent chemosensor was based on a mercapto rhodamine derivatives linked with Ag nanoparticles, and the Ag nanoparticles were supported on hexagonal mesoporous silica material (HMS). Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), absorption spectroscopy and fluorescence spectroscopy techniques were employed to characterize morphology, mesostructure and spectral features of the chemosensor. This chemosensor works in a nearly pure aqueous solution with a broad pH range. The output signals include color change and fluorescence. Moreover, HMS-Ag-R-2SH presents excellent anti-disturbance ability when exposed to a series of competitive cations such as Ag(+), K(+), Li(+), Na(+), Ba(2+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Mg(2+), Mn(2+), Ni(2+), Pb(2+), Zn(2+), Al(3+), Cr(3+) and Fe(3+). The selectivity of this chemosensor was significantly improved due to the introduction of the sulphydryl. The chemosensor showed a lower detection limit of 2.1ppb for Hg(2+). Importantly, HMS-Ag-R-2SH could be regenerated with sodium sulfide solution for several cycles and maintain a high sensitivity. PMID:25679802

Cheng, ZhuHong; Li, Gang; Liu, MeiMei

2015-04-28

178

Development of a microsphere-based fluorescence immunochromatographic assay for monitoring lincomycin in milk, honey, beef, and swine urine.  

PubMed

The residue of lincomycin (LIN) in edible animal foodstuffs caused by the widespread use of veterinary drugs is in need of rapid, simple, and sensitive detection methods. The present work introduces a fluorescent microsphere immunoassay (FMIA) for detecting LIN in different samples based on the competitive immunoreaction on the chromatography test strip. The residues of LIN in different samples compete with bovine serum albumin (BSA) labeled LIN conjugates on the T-line to bind to the anti-LIN monoclonal antibody labeled fluorescent microspheres (FM-mAbs). Captured FM-mAbs on the T-line represent the fluorescent intensity, which is detected under UV light and quantified by a fluorescent reader. Under optimized conditions, the dynamic range is from 1.35 to 3.57 ng/mL, and the 50% inhibition concentration (IC50) is 2.20 ng/mL. This method has 4.4% cross-reactivity with clindamycin and negligible cross-reactivity (<0.1%) with other analogues. To reduce the matrix effects, a dilution method is used to pretreat the samples, and the recoveries range from 73.92 to 120.50% with coefficient of variations <21.76%. In comparison with the results of ELISA and colloidal gold immunoassay, FMIA has obvious advantages such as easy operation, time savings, high sensitivity and specificity, and broader prospect. PMID:25290082

Zhou, Jie; Zhu, Kui; Xu, Fei; Wang, Wenjun; Jiang, Haiyang; Wang, Zhanhui; Ding, Shuangyang

2014-12-10

179

Dissolved oxygen sensing based on fluorescence quenching of ceria nanoparticles  

NASA Astrophysics Data System (ADS)

The development of oxygen sensors has positively impacted the fields of medical science, bioengineering, environmental monitoring, solar cells, industrial process control, and a number of military applications. Fluorescent quenching sensors have an inherent high sensitivity, chemical selectivity, and stability when compared to other types of sensors. While cerium oxide thin films have been used to monitor oxygen in the gas phase, the potential of cerium oxide (ceria) nanoparticles as the active material in sensor for oxygen gas has only recently been investigated. Ceria nanoparticles are one of the most unique nanomaterials that are being studied today due to the diffusion and reactivity of its oxygen vacancies, which contributes to its high oxygen storage capability. The reactivity of the oxygen vacancies, which is also related to conversion of cerium ion from the Ce+4 to Ce+3 state, affects the fluorescence properties of the ceria nanoparticles. Our research demonstrates that the ceria nanoparticles (~7 nm in diameter) have application as a fluorescence quenching sensor to measure dissolved oxygen in water. We have found a strong inverse correlation between the amplitude of the fluorescence emission (?excitation = 430 nm and ?peak = 520 nm) and the dissolved oxygen concentration between 5 - 13 mg/L. The Stern-Volmer constant, which is an indication of the sensitivity of gas sensing is 184 M-1 for the ceria nanoparticles. The results show that ceria nanoparticles can be used in an improved, robust fluorescence sensor for dissolved oxygen in a liquid medium.

Shehata, Nader; Meehan, Kathleen; Leber, Donald

2012-10-01

180

10 CFR Appendix W to Subpart B of... - Uniform Test Method for Measuring the Energy Consumption of Medium Base Compact Fluorescent Lamps  

Code of Federal Regulations, 2010 CFR

...for Measuring the Energy Consumption of Medium Base Compact Fluorescent Lamps W ...for Measuring the Energy Consumption of Medium Base Compact Fluorescent Lamps 1. Scope...rapid cycle stress, and lamp life of medium base compact fluorescent lamps....

2010-01-01

181

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

182

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

NASA Astrophysics Data System (ADS)

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

Yu, Miao; Wang, Wei; Zhang, Ning

183

Determination of beta-lactam antibiotics in water by fluorescence quenching of mercurochrome, and application for simple investigation of potency.  

PubMed

The fluorescence quenching reaction between fluorescein mercury or halogeno-fluorescein mercury compounds (fl. Hg, 2,7- or 2,4-dichloro-fl.Hg, 3',4',5',6'-tetrachloro-fl.Hg, mercurochrome) and beta-lactam antibiotics (ampicillin (AB-PC) and cephalexin (CEX] was investigated, and mercurochrome was selected for the detection of beta-lactam antibiotics; the detection limit was about 0.8 micrograms/ml. A fluorimetric assay of beta-lactam antibiotics was established by measuring the fluorescence of mercurochrome and mercurochrome-beta-lactam antibiotics solutions in weakly basic media to determine the degree of fluorescence quenching. The maximum emission wavelength of mercurochrome solution was at 544 nm with excitation at 470 nm. The calibration graphs were linear over the ranges of about 0-6 micrograms/ml beta-lactam antibiotics penicillins (AB-PC, penicillin G, sulbenicillin, amoxicillin, cyclacillin, oxacillin, hetacillin and piperacillin) and cepham antibiotics (CEX, cefazolin, cephaloglycin, cephaloridine and cefpyramide), and the relative standard deviation was 2.7% for 1.4 micrograms/ml of AB-PC (n = 5). This fluorescence quenching reaction between mercurochrome and beta-lactam antibiotics was applied in a survey of decomposition and remaining potency of beta-lactam antibiotics. PMID:2478306

Mori, I; Fujita, Y; Ikuta, K; Kitano, S; Kawabe, H; Nakahashi, Y; Kato, K; Inamori, Y

1989-07-01

184

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

PubMed

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

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

2014-12-29

185

An improved bimolecular fluorescence complementation tool based on superfolder green fluorescent protein.  

PubMed

Bimolecular fluorescence complementation (BiFC) has been widely used in the analysis of protein-protein interactions (PPIs) in recent years. There are many notable advantages of BiFC such as convenience and direct visualization of PPI in cells. However, BiFC has one common limitation: the separated non-fluorescent fragments can be spontaneously self-assembled into an intact protein, which leads to false-positive results. In this study, a pair of complementary fragments (sfGFPN and sfGFPC) was constructed by splitting superfolder GFP (sfGFP) between the 214 and 215 amino acid residue, and sfGFPC was mutated by site-directed gene mutagenesis to decrease the signal of negative control. Our results showed that mutations in sfGFPC (sfGFPC(m12)) can effectively decrease the signal of negative control. Thus, we provide an improved BiFC tool for the analysis of PPI. Further, since the self-assembly problem is a common shortcoming for application of BiFC, our research provides a feasible strategy for other BiFC candidate proteins with the same problem. PMID:21273204

Zhou, Jun; Lin, Jian; Zhou, Cuihong; Deng, Xiaoyan; Xia, Bin

2011-03-01

186

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

187

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

188

Fluorescence-Based Sensor for Monitoring Activation of Lunar Dust  

NASA Technical Reports Server (NTRS)

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

Wallace, William T.; Jeevarajan, Antony S.

2012-01-01

189

Cyclam-based "clickates": homogeneous and heterogeneous fluorescent sensors for Zn(II).  

PubMed

In an effort to improve upon the recently reported cyclam based zinc sensor 1, the "click"-generated 1,8-disubstituted analogue 2 has been prepared. The ligand shows a 2-fold increase in its fluorescence emission compared to 1 exclusively in the presence of Zn(II) that is typical of switch-on PET fluorescent sensors. Single crystal X-ray diffraction of complexes of model ligand 10 reveals that the configuration adopted by the macrocyclic framework is extremely sensitive to the metal ion to which it coordinates. For Zn(II), Mg(II), and Li(I) the metal ions adopt an octahedral geometry with a trans III configuration of the cyclam ring. In contrast for Ni(II) the ligand adopts the rare cis V configuration, while for Cu(II) a clear preference for five-coordinate geometry is displayed with a trans I configuration of the macrocyclic ring being observed in two essentially isostructural compounds prepared via different routes. The ligand displays an increased selectivity for Zn(II) compared to 1 in the majority of cases with excellent selectivity upheld over Na(I), Mg(II), Ca(II), Mn(II), Ni(II), Co(II), and Fe(III). In contrast for Cu(II) and Hg(II) little improvement was observed for 2 compared to 1 and for Cd(II) the selectivity of the new ligand was inferior. In the light of these findings and the slower response times for ligand 2, our original "click"-generated cyclam sensor system 1 was employed in a proof of concept study to prepare a heterogeneous sol-gel based material which retains its PET response to Zn(II). The versatile nature of the sol-gel process importantly allows the simple preparation of a variety of nanostructured materials displaying high surface area-volume ratio using fabrication methods such as soft lithography, electrospinning, and nanopipetting. PMID:20297799

Tamanini, Emiliano; Flavin, Kevin; Motevalli, Majid; Piperno, Silvia; Gheber, Levi A; Todd, Matthew H; Watkinson, Michael

2010-04-19

190

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

PubMed

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

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

2015-01-20

191

Autojoin: A Simple Rule Based Query Service for Complex Databases  

NASA Astrophysics Data System (ADS)

Most databases used today are no longer flat. While the power of using these more complex data stores is well known, construction of queries can be quite a complex task. Currently this often requires detailed knowledge of the database structure and schema. As we move towards a VO paradigm, users cannot be expected to know the structure of databases, but will need to query them. Databases will need to provide query engines to complete queries automatically given only what the user wants to have returned and any qualifications they place on the query. For years StarView, a database query and data retrieval tool for the Space Telescope Science Institute, relied on a complex third party LISP-based program (QUICK) to construct valid SQL queries for the one database it could query. This limited our ability to support StarView as we could not easily add new rules to the system without completely rebuilding the query engine. Furthermore, QUICK did not have the ability to create SQL that would join tables in different databases (but hosted on the same server). Finally, the cost of upgrading to a new version of QUICK was prohibitively high. Our solution was to develop a rather simple database table driven Perl CGI program which is able to take as its input a skeleton SQL program. This may come from a program or other web page. In the query only the SELECT and user qualified WHERE clause are specified; no FROM or WHERE clause join information is included. The service then returns a fully qualified and syntactically correct query for the host database SQL program that can be used to get the information the user needs. Thus, an additional layer of abstraction for dealing with databases is created, freeing the user from having to know how tables are related in the database. In this paper we discuss the design and algorithm used to make Autojoin work as well as discuss how, when combined with a robust and searchable description of all the fields that can be publicly queried in the database, it allows users to tailor their questions to the database with ease and a high rate of success.

Gaffney, N. I.; Gardner, L.; Brandt, M.

192

Time-domain imaging with quench-based fluorescent contrast agents  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

193

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

194

Fluorescence Molecular Tomography Based on a priori Information  

E-print Network

in order to achieve stable solutions, albeit with reduced resolution. Original FMT systems yielded-vivo by incorporating a priori anatomical information obtained from Magnetic Resonance Imaging into the optical to the use of near-infrared (NIR) fluorescent probes in order to achieve high detection sensitivity

Yazici, Birsen

195

Fluorescence based spectral assessment of pork meat freshness  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

196

Integrated microspectrometer for fluorescence based analysis in a microfluidic format.  

PubMed

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

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

2012-08-21

197

Adaptive finite element based tomography for fluorescence optical  

E-print Network

Wolfgang Bangerth,2 and Eva M. Sevick-Muraca1 1 Photon Migration Laboratories, Texas A & M University Society of America OCIS codes: (170.3010) Image Reconstruction Techniques; (170.5280) Photon Migration resolution fluorescence molecular imaging system for small animal imaging," Med. Phys. 30, 901­911 (2003). (C

Bangerth, Wolfgang

198

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

199

Synchronous fluorescence determination of ciprofloxacin in the pharmaceutical formulation and human serum based on the perturbed luminescence of rare-earth ions  

Microsoft Academic Search

A simple, rapid and sensitive synchronous fluorescence method was developed for the determination of ciprofloxacin (CPFX) in the pharmaceutical formulation and human serum. The results show that when Y3+ is added into the CPFX solution, the characteristic fluorescence of Y3+ is not emitted whereas the fluorescence intensity of CPFX is significantly enhanced. The synchronous fluorescence technology is employed in this

Changlun Tong; Xiajun Zhuo; Yun Guo; Yueheng Fang

2010-01-01

200

Multi-projection based fluorescence optical tomography using a hand-held probe based optical imager  

NASA Astrophysics Data System (ADS)

Hand-held based optical imagers have become a new research interest for its maximum patient comfort, less bulky instrument and potential for clinical translation towards breast cancer diagnostics. However, its ability for optical tomography is either limited by depth recovery since only reflectance measurements were obtained using a hand-held design for imaging. In this study, we introduced a self-guided multi-projection technique, which can take advantage of potential portability of hand-held probe based system, towards improvement of target depth recovery during fluorescence optical tomography studies.

Ge, Jiajia; Erickson, Sarah J.; Godavarty, Anuradha

2009-02-01

201

The measurement of delayed fluorescence in an acrylic based scintillation detector  

E-print Network

THE MEASUREMENT OF DELAYED FLUORESCENCE IN AN ACRYLIC BASED SCINTILLATION DETECTOR A Thesis by CHI-HO HONG Submitted to the Graduate College of Texas A&M University in partial fulfillment of the require ment for the degree of MASTER... OF SCIENCE December 1987 Major Subject: Physics THE MEASUREMENT OF DELAYED FLUORESCENCE IN AN ACRYLIC BASED SCINTILLATION DETECTOR A Thesis CHI-HO HONG Approved as to style and content by: Robert C. Webb (Chairman of Committee) aryl . Di itonto...

Hong, Chi-Ho

1987-01-01

202

The development of chlorophyll-based markers in poultry diets to aid detection of fluorescent fecal contamination.  

PubMed

Incidents of foodborne illness associated with consuming undercooked or raw chicken are often linked to 2 causative pathogens: Campylobacter spp. or Salmonella spp. Numerous studies have shown that contamination of carcasses results when pathogens are transferred from the intestinal tract or fecal material on feet and feathers to the dressed carcass. Ultraviolet spectral imaging to detect surface fecal and ingesta contamination on poultry carcasses may provide a solution to aid detection. However, poultry diets do not provide sufficiently high levels of natural fluorophores for this system to be reliable. This study investigated the potential of chlorophyll-based feed additives to improve fluorescence of the feces and narrow the excitation and emission wavelengths to aid in the development of a simple visualization system. Twenty-four hens (Gallus gallus domesticus) were allocated at random to 1 of 4 treatments: control (C, no marker), Zn chlorophyllin, Mg chlorophyllin, or Fe chlorophyllin. All markers were incorporated into mash before pelleting at a rate of 1 g/kg of DM. The experiment consisted of two 4 × 4 Latin squares with each period consisting of 2 wk. Feces were collected and extracted in acetone:water (50:50; vol/vol) with fecal fluorescence emission spectra determined using a Jasco FP-6200 Spectrofluorometer with excitation at 382 nm. A main peak evolved at wavelength 670 nm with the total area under the peak used as fluorescence intensity. Following 7 d of marker supplementation, the 3 markers improved the fluorescence intensity by ×14.8, 12.8, and 6.9 for Fe, Mg, and Zn chlorophyllin, respectively, compared with the control. The addition of feces containing Mg chlorophyllin to chicken carcass increased detection of the feces compared with feces with no marker. Also, due to the plain background of chicken skin, a simple image at 675 nm with appropriate thresholds would allow detection of contaminated carcasses at the current slaughter line speed without the need of expensive hyperspectral imaging. PMID:24235236

Lee, M R F; Leemans, D; Theobald, V J; Fleming, H R; Gay, A P

2013-12-01

203

Switching properties of fluorescent photochromic poly(methyl methacrylate) with spironaphthoxazine and D-?-A type pyran-based fluorescent dye  

NASA Astrophysics Data System (ADS)

Fluorescent photochromic poly(methyl methacrylate) (PMMA) with spironaphthoxazine (SPO) and D-?-A type pyran-base fluorescent dye as a fluorophore was synthesized by typical free radical copolymerization. The poly(MMA- co-SPO- co-fluorophore) in both solution and solid film exhibited excellent photoregulated fluorescence switching behavior and reversible modulation of fluorescence intensity using alternating irradiation with UV and visible light. The poly(MMA- co-SPO- co-fluorophore) also showed viscosity and conductivity switching behaviors along with photoresponse.

Lee, Eun-Mi; Gwon, Seon-Young; Son, Young-A.; Kim, Sung-Hoon

2012-02-01

204

A new boronic acid fluorescent sensor based on fluorene for monosaccharides at physiological pH.  

PubMed

Fluorescent boronic acids are very useful fluorescent sensor for detection of biologically important saccharides. Herein we synthesized a new fluorene-based fluorescent boronic acid that shows significant fluorescence changes upon addition of saccharides at physiological pH. Upon addition of fructose, sorbitol, glucose, galactose, ribose, and maltose at different concentration to the solution of 7-(dimethylamino)-9,9-dimethyl-9H-fluoren-2-yl-2-boronic acid (7-DMAFBA, 1), significant decreases in fluorescent intensity were observed. It was found that this boronic acid has high affinity (Ka=3582.88M(-1)) and selectivity for fructose over glucose at pH=7.4. The sensor 1 showed a linear response toward d-fructose in the concentrations ranging from 2.5×10(-5) to 4×10(-4)molL(-1) with the detection limit of 1.3×10(-5)molL(-1). PMID:25748592

Hosseinzadeh, Rahman; Mohadjerani, Maryam; Pooryousef, Mona; Eslami, Abbas; Emami, Saeed

2015-06-01

205

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

PubMed

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

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

2015-04-01

206

Lanthanide based dual-emission fluorescent probe for detection of mercury (II) in milk.  

PubMed

It is highly desirable to develop a simple and sensitive method for Hg(2+) detection because of the dangerous nature of Hg(2+). In this work, we prepared a dual-emission fluorescent probe for Hg(2+) detection by combining two lanthanide chelates with different emission wavelengths. Green-emitting terbium (Tb(3+)) chelates as reference signals were embedded into SiO2 nanoparticles and red-emitting europium (Eu(3+)) chelates as response units were covalently linked to the surface of silica shell. Upon the addition of Hg(2+), the fluorescence of Eu(3+) chelates can be selectively quenched, while the fluorescence of Tb(3+) chelates remained unchanged. As a kind of Hg(2+) nanosensor, the dual-emission fluorescent probe exhibited excellent selectivity to Hg(2+) and high sensitivity up to 7.07 nM detection limit. The Hg(2+) levels in drinking water and milk samples were determined by using the dual-emission fluorescent probe with satisfied recovery. Additionally, our probe has a long enough fluorescence lifetime, which can avoid the interference from autofluorescence of the biological samples. We envision that the proposed probe could find great potential applications for ultrasensitive time-resolved fluorometric assays and biomedical imaging in the future. PMID:25168765

Tan, Hongliang; Li, Qian; Ma, Chanjiao; Song, Yonghai; Xu, Fugang; Chen, Shouhui; Wang, Li

2015-01-15

207

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

208

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

209

Fluorescent Protein-Based Methods for On-Plate Screening of Gene Insertion  

PubMed Central

Background Unlike the commonly used method of blue-white screening for gene insertion, a fluorescent protein-based screening method offers a gain-of-function screening process without using any co-factors and a gene fusion product with a fluorescent protein reporter that is further useful in cell imaging studies. However, complications related to protein-folding efficiencies of the gene insert in fusion with fluorescent protein reporters prevent effective on-plate bacterial colony selection leading to its limited use. Methodology/Principal Findings Here, we present three methods to tackle this problem. Our first method promotes the folding of the gene insert by using an N-terminal protein such as calmodulin that is well folded and expressed. Under this method, fluorescence was increased more than 30x over control allowing for enhanced screening. Our second method creates a fluorescent protein that is N-terminal to the gene upon insertion, thereby reducing the dependency of the fluorescent protein reporter on the folding of the gene insert. Our third method eliminates any dependence of the fluorescent protein reporter on the folding of the gene insert by using a stop and start sequence for protein translation. Conclusions/Significance The three methods together will expand the usefulness of fluorescence on-plate screening and offer a powerful alternative to blue-white screening. PMID:21170317

Wong, Stanley S. C.; Truong, Kevin

2010-01-01

210

Organic fluorescent thermometers based on borylated arylisoquinoline dyes.  

PubMed

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

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

2014-06-16

211

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

212

Structured light sheet fluorescence microscopy based on four beam interference.  

PubMed

A 3D structured light sheet microscope using a four-faceted symmetric pyramid is presented. The sample is illuminated by the resulting four beam interference field. This approach combines advantages of standing wave and structured illumination microscopy. Examples of micrographs of fluorescently labeled Chinese hamster ovary (CHO) cells as well as of the compound eyes of drosophila are shown and the optical sectioning ability of our system is demonstrated. The capabilities and the limitations of the scheme are discussed. PMID:20940819

Lei, Ming; Zumbusch, Andreas

2010-08-30

213

Computed tomography based spectral imaging for fluorescence microscopy  

NASA Astrophysics Data System (ADS)

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

Ford, Bridget Kathleen

214

Computed Tomography-Based Spectral Imaging For Fluorescence Microscopy  

Microsoft Academic Search

The computed tomography imaging spectrometer (CTIS) is a non-scanning instrument capable of simultaneously acquiring full spectral information (450–750nm) from every position element within its field of view (75?m×75?m). The current spatial and spectral sampling intervals of the spectrometer are 1.0?m and 10nm, respectively. This level of resolution is adequate to resolve signal responses from multiple fluorescence probes located within individual

Bridget K. Ford; Curtis E. Volin; Sean M. Murphy; Ronald M. Lynch; Michael R. Descour

2001-01-01

215

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

216

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

217

Time resolved fluorescence tomography of turbid media based on lifetime contrast  

PubMed Central

A general linear model for time domain (TD) fluorescence tomography is presented that allows a lifetime-based analysis of the entire temporal fluorescence response from a turbid medium. Simulations are used to show that TD fluorescence tomography is optimally performed using two complementary approaches: A direct TD analysis of a few time points near the peak of the temporal response, which provides superior resolution; and an asymptotic multi-exponential analysis based tomography of the decay portion of the temporal response, which provides accurate localization of yield distributions for various lifetime components present in the imaging medium. These results indicate the potential of TD technology for biomedical imaging with lifetime sensitive targeted probes, and provide useful guidelines for an optimal approach to fluorescence tomography with TD data. PMID:19529654

Kumar, Anand T. N.; Raymond, Scott B.; Boverman, Gregory; Boas, David A.; Bacskai, Brian J.

2009-01-01

218

Fluorescence Tomographic Imaging using a Hand-held Probe based Optical Imager: Extensive Phantom Studies  

PubMed Central

Hand-held probe based optical imagers are popular towards breast imaging due to their potential portability and maximum patient comfort. Recently, a novel hand-held probe based optical imager has been developed and its feasibility for three-dimensional fluorescence tomographic imaging demonstrated. Herein, extensive tomography studies were performed on large slab phantoms (650 ml) in order to assess the performance limits of the hand-held imager. Experiments were performed using different target volumes (0.1–0.45 cc), target depths (1–3 cm), and fluorescence (Indocyanine Green) absorption contrast ratios in a non-fluorescing (1:0) and constant fluorescing backgrounds (1000:1-5:1). The estimated sensitivity and specificity of the hand-held imager is 43% and 95%, respectively. PMID:19935959

Ge, Jiajia; Erickson, Sarah J.; Godavarty, Anuradha

2010-01-01

219

A Parallel Reconstruction Scheme in Fluorescence Tomography Based on Contrast of Independent Inversed Absorption Properties  

PubMed Central

Based on an independent forward model in fluorescent tomography, a parallel reconstructed scheme for inhomogeneous mediums with unknown absorption property is proposed in this paper. The method considers the two diffusion equations as separately describing the propagation of excited light in tissues with and without fluorescent probes inside. Then the concentration of fluorophores is obtained directly through the difference between two estimations of absorption coefficient which can be parallel inversed. In this way, the multiparameter estimation problem in fluorescent tomography is transformed into two independent single-coefficient determined schemes of diffusion optical tomography (DOT). Any algorithms proved to be efficient and effective in DOT can be directly applied here. In this study the absorption property is estimated from the independent diffusion equations by a gradient-based optimization method with finite element method (FEM) solving the forward model. Simulation results of three representative occasions show that the reconstructed method can well estimate fluorescent property and tissue absorption distribution. PMID:23165045

Yi, Ji; Bai, Jing

2006-01-01

220

A human kringle domain-based fluorescence-linked immunosorbent assay system.  

PubMed

As a non-immunoglobulin protein scaffold, human kringle domain (KD) has attractive properties such as high specificity, stability, and production in bacterial hosts. Here, we developed a rapid and sensitive fluorescence-linked immunosorbent assay (FLISA) system using a fluorescent kringle domain (fluoKD), a fusion protein of a green fluorescent protein (GFP), and a kringle domain variant (KD548). Two kinds of fluoKDs in which KD was fused to the N terminus of GFP (N-fluoKD) or the C terminus of GFP (C-fluoKD) were constructed and characterized. In Escherichia coli host, both fluoKDs were produced in high yield and solubility and were successfully purified by a simple procedure. The purified fluoKDs exhibited strong fluorescent activities and high affinities to the target antigen. Furthermore, it was successfully demonstrated that the FLISA with purified fluoKDs allowed for more rapid detection of target antigens with higher sensitivity compared with conventional enzyme-linked immunosorbent assay (ELISA), indicating that a simple, rapid, and sensitive immunoassay system could be developed by using KD instead of antibody or antibody fragments. PMID:24525040

Jeong, Gu Min; Kim, Yong Sung; Jeong, Ki Jun

2014-04-15

221

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

Microsoft Academic Search

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

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

222

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

Microsoft Academic Search

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

Fenghong Chu; Haiwen Cai; Ronghui Qu; Zujie Fang

2007-01-01

223

Room-temperature single-photon sources based on nanocrystal fluorescence in photonic/plasmonic nanostructures  

NASA Astrophysics Data System (ADS)

Results are presented here towards robust room-temperature SPSs based on fluorescence in nanocrystals: colloidal quantum dots, color-center diamonds and doped with trivalent rare-earth ions (TR3+). We used cholesteric chiral photonic bandgap and Bragg-reflector microcavities for single emitter fluorescence enhancement. We also developed plasmonic bowtie nanoantennas and 2D-Si-photonic bandgap microcavities. The paper also provides short outlines of other technologies for room-temperature single-photon sources.

Lukishova, S. G.; Winkler, J. M.; Bissell, L. J.; Mihaylova, D.; Liapis, Andreas C.; Shi, Z.; Goldberg, D.; Menon, V. M.; Boyd, R. W.; Chen, G.; Prasad, P.

2014-10-01

224

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

PubMed

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

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

2012-09-01

225

A new Schiff-base type selective fluorescent chemosensor for Cu 2+  

Microsoft Academic Search

An original Schiff-base type fluorescent chemosensor 1-phenyl-3-methyl-5-hydroxypyrazole-4-carbaldehyde(benzoyl)hydrazone (H2L) for Cu2+ has been designed and synthesized. An obvious fluorescence quenching only for Cu2+ demonstrates that ligand H2L exhibits high selectivity and efficient signaling behavior toward micromolar concentration of Cu2+ compared with other metal ions. At the same time, the coordination form between ligand and Cu2+ is elucidated via crystal structure.

Hong-Ge Li; Zheng-Yin Yang; Dong-Dong Qin

2009-01-01

226

Fluorescence intensity and lifetime-based cyanide sensitive probes for physiological safeguard  

Microsoft Academic Search

We characterize six new fluorescent probes that show both intensity and lifetime changes in the presence of free uncomplexed aqueous cyanide, allowing for fluorescence based cyanide sensing up to physiological safeguard levels, i.e. <30?M. One of the probes, m-BMQBA, shows a ?15-fold reduction in intensity and a ?10% change in mean lifetime at this level.The response of the new probes

Ramachandram Badugu; Joseph R. Lakowicz; Chris D. Geddes

2004-01-01

227

Gold Nanoparticle-Based Fluorescence Resonance Energy Transfer Aptasensor for Ochratoxin a Detection  

Microsoft Academic Search

In this paper, a sensitive and specific fluorescence resonance energy transfer (FRET) aptasensor for the detection of Ochratoxin A (OTA) is developed based on a dye-tagged ssDNA hybridized with aptamer-conjugated Au nanoparticles (Au NPs). The binding between the aptamer-Au NPs conjugate and the dye-labeled ssDNA leads to the fluorescence quenching of FAM due to its close proximity. The addition of

Nuo Duan; Shijia Wu; Xiaoyuan Ma; Xiujuan Chen; Yukun Huang; Zhouping Wang

2012-01-01

228

Fluorescence polarization immunoassay for salinomycin based on monoclonal antibodies  

Microsoft Academic Search

A fluorescence polarization immunoassay (FPIA) for the determination of salinomycin (SAL) was developed by using anti-SAL\\u000a monoclonal antibodies (mAb). Fluorescein labeled SAL (tracer) was synthesized by the N-hydroxysuccinimide active ester method\\u000a and purified using thin layer chromatography (TLC). The developed FPIA for SAL had a dynamic range from 0.60 to 2193 ng\\/mL\\u000a with an IC50 value of 33.2 ng\\/mL and

ZhanHui Wang; LinLi Cheng; WeiMin Shi; SuXia Zhang; JianZhong Shen

2010-01-01

229

A simple machine [based on the SK-combinator reduction mechanism  

Microsoft Academic Search

A simple machine architecture based on an extension to the combinator notation is described. Code travels along a unidirectional stream and is executed in parallel by simple finite state machine based cells separated by sections of a first-in, first-out (FIFO) buffer. The resulting regularity and structural simplicity ensure a good match to VLSI implementation. It is verified that the extended

Alex Dickinson; Michael T. Pope

1992-01-01

230

Simple, benign, aqueous-based amination of polycarbonate surfaces.  

PubMed

Polycarbonate is a desirable material for many applications due to its favorable mechanical and optical properties. Here, we report a simple, safe, environmentally friendly aqueous method that uses diamines to functionalize a polycarbonate surface with amino groups. The use of water as the solvent for the functionalization ensures that solvent induced swelling does not affect the optical or mechanical properties of the polycarbonate. We characterize the efficacy of the surface amination using X-ray photo spectroscopy, Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), and contact angle measurements. Furthermore, we demonstrate the ability of this facile method to serve as a foundation upon which other functionalities may be attached, including antifouling coatings and oriented membrane proteins. PMID:25695347

VanDelinder, Virginia; Wheeler, David R; Small, Leo J; Brumbach, Michael T; Spoerke, Erik D; Henderson, Ian; Bachand, George D

2015-03-18

231

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

232

Fluorescent thiophene-based materials and their outlook for emissive applications.  

PubMed

Although thiophene-based materials are among the most widely studied conjugated materials for a number of technological applications, most discussions of emissive conjugated materials have focused on other systems, primarily due to the lower emission quantum yields of thiophene-based systems. Over the last decade, however, this has begun to change with the development of new highly emissive thiophene-based materials. In this review, we provide an overview of fluorescent thiophene-based materials and their applications, highlighting in particular the various methods employed to achieve highly emissive materials, as well as a variety of reported applications including fluorescent biomarkers and organic light emitting diodes. PMID:25622008

Rasmussen, Seth C; Evenson, Sean J; McCausland, Casey B

2015-03-01

233

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

PubMed

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

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

2014-11-26

234

Energy transfer: nearly 100% triplet harvesting in conventional fluorescent dopant-based organic light-emitting devices through energy transfer from exciplex (adv. Mater. 12/2015).  

PubMed

On page 2025, C.-J. Zheng, X.-H. Zhang, C.-S. Lee, and co-workers report a conventional fluorescent-dopant-based organic light-emitting device (OLED) with an external quantum efficiency as high as 14.5%, close to nearly 100% triplet harvesting, through energy transfer from the exciplex. This device concept represents a simple and fruitful approach for getting high-efficiency, low-operating-voltage OLEDs with good color purities. PMID:25800628

Liu, Xiao-Ke; Chen, Zhan; Zheng, Cai-Jun; Chen, Miao; Liu, Wei; Zhang, Xiao-Hong; Lee, Chun-Sing

2015-03-01

235

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

PubMed

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

Kaur, Matinder; Choi, Dong Hoon

2015-01-01

236

Magnetic quantum tunneling: insights from simple molecule-based magnets.  

PubMed

This perspectives article takes a broad view of the current understanding of magnetic bistability and magnetic quantum tunneling in single-molecule magnets (SMMs), focusing on three families of relatively simple, low-nuclearity transition metal clusters: spin S = 4 Ni(II)(4), Mn(III)(3) (S = 2 and 6) and Mn(III)(6) (S = 4 and 12). The Mn(III) complexes are related by the fact that they contain triangular Mn(III)(3) units in which the exchange may be switched from antiferromagnetic to ferromagnetic without significantly altering the coordination around the Mn(III) centers, thereby leaving the single-ion physics more-or-less unaltered. This allows for a detailed and systematic study of the way in which the individual-ion anisotropies project onto the molecular spin ground state in otherwise identical low- and high-spin molecules, thus providing unique insights into the key factors that control the quantum dynamics of SMMs, namely: (i) the height of the kinetic barrier to magnetization relaxation; and (ii) the transverse interactions that cause tunneling through this barrier. Numerical calculations are supported by an unprecedented experimental data set (17 different compounds), including very detailed spectroscopic information obtained from high-frequency electron paramagnetic resonance and low-temperature hysteresis measurements. Comparisons are made between the giant spin and multi-spin phenomenologies. The giant spin approach assumes the ground state spin, S, to be exact, enabling implementation of simple anisotropy projection techniques. This methodology provides a basic understanding of the concept of anisotropy dilution whereby the cluster anisotropy decreases as the total spin increases, resulting in a barrier that depends weakly on S. This partly explains why the record barrier for a SMM (86 K for Mn(6)) has barely increased in the 15 years since the first studies of Mn(12)-acetate, and why the tiny Mn(3) molecule can have a barrier approaching 60% of this record. Ultimately, the giant spin approach fails to capture all of the key physics, although it works remarkably well for the purely ferromagnetic cases. Nevertheless, diagonalization of the multi-spin Hamiltonian matrix is necessary in order to fully capture the interplay between exchange and local anisotropy, and the resultant spin-state mixing which ultimately gives rise to the tunneling matrix elements in the high symmetry SMMs (ferromagnetic Mn(3) and Ni(4)). The simplicity (low-nuclearity, high-symmetry, weak disorder, etc.) of the molecules highlighted in this study proves to be of crucial importance. Not only that, these simple molecules may be considered among the best SMMs: Mn(6) possesses the record anisotropy barrier, and Mn(3) is the first SMM to exhibit quantum tunneling selection rules that reflect the intrinsic symmetry of the molecule. PMID:20405069

Hill, Stephen; Datta, Saiti; Liu, Junjie; Inglis, Ross; Milios, Constantinos J; Feng, Patrick L; Henderson, John J; del Barco, Enrique; Brechin, Euan K; Hendrickson, David N

2010-05-28

237

A simple purification and fluorescent assay method of the poliovirus 3C protease searching for specific inhibitors  

Microsoft Academic Search

Picornaviruses such as poliovirus, foot-and-mouth disease virus, and encephalomyocarditis virus produce their proteins by translating their genomic RNA, injected within the host cell, into a precursor polyprotein, which is then subjected to precise processing. The polyprotein is cleaved into mature proteins predominantly by the viral 3C protease. A simple purification and assay method for poliovirus 3C protease for use for

Shoji Hata; Taisuke Sato; Hiroyuki Sorimachi; Shoichi Ishiura; Koichi Suzuki

2000-01-01

238

A novel, simple and efficient dye laser with low amplified spontaneous emission background for analytical fluorescence and ionization spectroscopy  

SciTech Connect

A new, simple, compact and efficient, grazing- incidence type of dye laser is suggested which has a low level of Amplified Spontaneous Emission. By using a Coumarin dye (LD 5000) pumped with a 20 mJ XeCl excimer laser, and a diffraction grating with 3000 grooves/mm, an efficiency of 11%, a spectral bandwidth of 0.6 cm{sup -1} and a tuning range from 458 to 517 nm have been obtained.

Matveev, Oleg I.; Omenetto, Nicolo' [EC, Joint Research Centre, Environment Institute, 21020 Ispra, Varese (Italy)

1995-04-01

239

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

PubMed Central

To increase the diversity of fluorescent base analogues with improved properties, we here present the straightforward click-chemistry-based synthesis of a novel fluorescent adenine-analogue triazole adenine (AT) and its photophysical characterization inside DNA. AT shows promising properties compared to the widely used adenine analogue 2-aminopurine. Quantum yields reach >20% and >5% in single- and double-stranded DNA, respectively, and show dependence on neighbouring bases. Moreover, AT shows only a minor destabilization of DNA duplexes, comparable to 2-aminopurine, and circular dichroism investigations suggest that AT only causes minimal structural perturbations to normal B-DNA. Furthermore, we find that AT shows favourable base-pairing properties with thymine and more surprisingly also with normal adenine. In conclusion, AT shows strong potential as a new fluorescent adenine analogue for monitoring changes within its microenvironment in DNA. PMID:21278417

Dierckx, Anke; Dinér, Peter; El-Sagheer, Afaf H.; Kumar, Joshi Dhruval; Brown, Tom; Grøtli, Morten; Wilhelmsson, L. Marcus

2011-01-01

240

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

PubMed Central

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

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

2008-01-01

241

Patch-based Markov models for event detection in fluorescence bioimaging.  

PubMed

The study of protein dynamics is essential for understanding the multi-molecular complexes at subcellular levels. Fluorescent Protein (XFP)-tagging and time-lapse fluorescence microscopy enable to observe molecular dynamics and interactions in live cells, unraveling the live states of the matter. Original image analysis methods are then required to process challenging 2D or 3D image sequences. Recently, tracking methods that estimate the whole trajectories of moving objects have been successfully developed. In this paper, we address rather the detection of meaningful events in spatio-temporal fluorescence image sequences, such as apparent stable "stocking areas" involved in membrane transport. We propose an original patch-based Markov modeling to detect spatial irregularities in fluorescence images with low false alarm rates. This approach has been developed for real image sequences of cells expressing XFP-tagged Rab proteins, known to regulate membrane trafficking. PMID:18982594

Pécot, Thierry; Kervrann, Charles; Bardin, Sabine; Goud, Bruno; Salamero, Jean

2008-01-01

242

Assessment of dental demineralization of yellow race based on fluorescence spectrum  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

243

"Off-on" aggregation-based fluorescent sensor for the detection of chloride in water.  

PubMed

Receptors selective for anions in aqueous media are a crucial component in the detection of anions for biological and environmental applications. Recent sensor designs have taken advantage of systems known to aggregate in solution, eliciting a fluorescent response. Herein, we demonstrate a chloride-selective fluorescent response of receptor 1(+), based on our well-established class of 2,6-bis(2-anilinoethynyl)pyridine bisureas. The fluorescence intensity ratio of 1(+)·Cl(->) aggregates in water is four times larger than the next most fluorescent anion complex, 1(+)·ClO4(->). In addition, (1)H NMR spectroscopic titrations demonstrate 1(+) binds chloride more strongly than other biologically relevant anions in solutions of both DMSO-d6 and 50/50 DMSO-d6/MeCN-d3. PMID:25758666

Watt, Michelle M; Engle, Jeffrey M; Fairley, Kurtis C; Robitshek, Timothy E; Haley, Michael M; Johnson, Darren W

2015-04-14

244

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

245

Fluorescent-based chemical sensor for organophosphate detection  

NASA Astrophysics Data System (ADS)

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

Urek, Špela Korent; Lobnik, Aleksandra

2011-05-01

246

A fluorescence-based screen for ribosome binding antibiotics  

PubMed Central

The development of new antibacterial agents has become necessary to treat the large number of emerging bacterial strains resistant to current antibiotics. Despite the different methods of resistance developed by these new strains, the A-site of the bacterial ribosome remains an attractive target for new antibiotics. To develop new drugs that target the ribosomal A-site, a high-throughput screen is necessary to identify compounds that bind to the target with high affinity. To this end, we present an assay that uses a novel fluorescein-conjugated neomycin (F-neo) molecule as a binding probe to determine the relative binding affinity of a drug library. We show here that the binding of F-neo to a model Escherichia coli ribosomal A-site results in a large decrease in the fluorescence of the molecule. Furthermore, we have determined that the change in fluorescence is due to the relative change in the pKa of the probe resulting from the change in the electrostatic environment that occurs when the probe is taken from the solvent and localized into the negative potential of the A-site major groove. Finally, we demonstrate that F-neo can be used in a robust, highly reproducible assay, determined by a Z?-factor greater than 0.80 for 3 consecutive days. The assay is capable of rapidly determining the relative binding affinity of a compound library in a 96-well plate format using a single channel electronic pipette. The current assay format will be easily adaptable to a high-throughput format with the use of a liquid handling robot for large drug libraries currently available and under development. PMID:23262284

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

2014-01-01

247

Simple adaptive control for SISO nonlinear systems using neural network based on genetic algorithm  

Microsoft Academic Search

This paper presents a method of continuous-time simple adaptive control (SAC) using neural network based on genetic algorithm (GA) for a single-input single-output (SISO) nonlinear systems, bounded-input bounded-output, and bounded nonlinearities. According to the power of neural network and the characteristics of simple adaptive control, constructed a simple adaptive control using neural networks, and in neural network learning process, introduce

Shi-Qi An; Tian Lu; Yu-Ju Ma

2010-01-01

248

Simple Location-based Application Development for Mobile Phones  

Microsoft Academic Search

This paper gives an overview about some of the most important components and services necessary to build location- based applications. As a practical example, it is described how a mobile device can estimate current position using a GPS receiver and how the information regarding our location is uploaded to an application server.

D. Titica; O. Fratu; E. Stanescu; S. Halunga-Fratu

2007-01-01

249

A simple raster-based model for flood inundation simulation  

Microsoft Academic Search

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

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

2000-01-01

250

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

251

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

Microsoft Academic Search

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

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

2006-01-01

252

A synthetic amino acid residue containing a new oligopeptide-based photosensitive fluorescent organogel.  

PubMed

A synthetic amino acid (with a stilbene residue in the main chain) containing a tripeptide-based organogelator has been discovered. This peptide-based synthetic molecule 1 self-assembles in various organic solvents to form an organogel. The gel has been thoroughly characterized by using various microscopic techniques including field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), UV-visible and fluorescence spectroscopy, and rheology. Morphological investigations using FESEM and AFM show a nanofibrillar network structure. Interestingly, the organogel is photoresponsive and a gel-sol transition occurred by irradiating the gel with UV light of 365 nm for 2 h as shown by the UV and fluorescence study. This photoresponsive fluorescent gel holds promise for new peptide-based soft materials with interesting applications. PMID:23086712

Maiti, Dibakar Kumar; Banerjee, Arindam

2013-01-01

253

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

254

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

DOEpatents

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

Mayer-Cumblidge, M. Uljana (Richland, WA); Cao, Haishi (Richland, WA)

2010-08-17

255

[Lake algae chemotaxonomy technology based on fluorescence excitation emission matrix and parallel factor analysis].  

PubMed

An in vivo three-dimensional fluorescence method for the determination of algae community structure was developed by parallel factor (PARAFAC) analysis and CHEMTAX. The PARAFAC model was applied to fluorescence excitation-emission matrix (EEM) of 23 algae species and 12 fluorescent components were identified according to the residual sum of squares and specificity of the composition profiles of fluorescent. Based on the 12 fluorescent components, the algae species at different growth stages were correctly classified at the division level using Bayesian discriminant analysis (BDA). Then the reference fluorescent component ratio matrix was constructed for CHEMTAX, and the EEM-PARAFAC-CHEMTAX method was developed to differentiate taxonomic groups of algae. When the fluorometric method was used for 531 single-species samples, the average correct discrimination ratio (CDR) was 99.1% and the correct discrimination ratios (CDRs) were 100% at the division level except Chlorophyta, the CDR of which was 97.5%. The CDRs for 95 mixtures were above 98.5% for the dominant algae species and above 90.5% for the subdominant algae species, with average relative contents of 69.7% and 26.4%, respectively. This technique would be of great aid when low-cost and rapid analysis is needed for samples in a large batch. PMID:24881379

Chen, Xiao-Na; Han, Xiu-Rong; Su, Rong-Guo; Shi, Xiao-Yong

2014-03-01

256

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

E-print Network

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

Prentiss, Mara

257

A reusable DNA single-walled carbon-nanotube-based fluorescent sensor for highly sensitive and selective detection of Ag+ and cysteine in aqueous solutions.  

PubMed

Here we report a reusable DNA single-walled carbon nanotube (SWNT)-based fluorescent sensor for highly sensitive and selective detection of Ag(+) and cysteine (Cys) in aqueous solution. SWNTs can effectively quench the fluorescence of dye-labeled single-stranded DNA due to their strong pi-pi stacking interactions. However, upon incubation with Ag(+), Ag(+) can induce stable duplex formation mediated by C-Ag(+)-C (C=cytosine) coordination chemistry, which has been further confirmed by DNA melting studies. This weakens the interactions between DNA and SWNTs, and thus activates the sensor fluorescence. On the other hand, because Cys is a strong Ag(+) binder, it can remove Ag(+) from C-Ag(+)-C base pairs and deactivates the sensor fluorescence by rewrapping the dye-labeled oligonucleotides around the SWNT. In this way, the fluorescence signal-on and signal-off of a DNA/SWNT sensor can be used to detect aqueous Ag(+) and Cys, respectively. This sensing platform exhibits high sensitivity and selectivity toward Ag(+) and Cys versus other metal ions and the other 19 natural amino acids, with a limit of detection of 1 nM for Ag(+) and 9.5 nM for Cys. Based on these results, we have constructed a reusable fluorescent sensor by using the covalent-linked SWNT-DNA conjugates according to the same sensing mechanism. There is no report on the use of SWNT-DNA assays for the detection of Ag(+) and Cys. This assay is simple, effective, and reusable, and can in principle be used to detect other metal ions by substituting C-C base pairs with other native or artificial bases that selectively bind to other metal ions. PMID:20512822

Zhao, Chao; Qu, Konggang; Song, Yujun; Xu, Can; Ren, Jinsong; Qu, Xiaogang

2010-07-19

258

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

PubMed Central

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

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

2014-01-01

259

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

260

Poly(m-phenylenediamine)-based fluorescent nanoprobe for ultrasensitive detection of matrix metalloproteinase 2.  

PubMed

A novel fluorescence nanoprobe for the detection of matrix metalloproteinase 2 (MMP2) has been developed by engineering the fluorescein isothiocyanate-labeled peptide onto the surface of poly(m-phenylenediamine) (PMPD) nanoparticles through covalent linkage. The nanoprobe itself displays a low background signal due to the effective fluorescence quenching by electron-rich PMPD, but its reaction with MMP2 causes 11-fold fluorescence enhancement. Compared with similar fluorescence nanosystems for MMP2 assembled through physical adsorption, the as-prepared nanoprobe is significantly more stable and displays a strikingly higher signal-to-background ratio, which leads to a high sensitivity for MMP2 assay, with a detection limit of 32 pM. Most notably, the nanoprobe has been successfully applied to determine MMP2 in human serum samples, demonstrating that the MMP2 level in serum from colorectal cancer (CRC) patients is 2 times higher than that from healthy people. Moreover, the nanoprobe has also been used to monitor MMP2 secreted by CRC cells that were grown under normoxic and hypoxic conditions, respectively, and the results show that the cells under hypoxic conditions produce higher level of MMP2 than those under normoxic conditions. Our method is simple and can offer a highly sensitive detection of MMP2 in relevant clinical samples. PMID:25029076

Wang, Zhe; Li, Xiaohua; Feng, Duan; Li, Lihong; Shi, Wen; Ma, Huimin

2014-08-01

261

Evaluation of a Fluorescence-Based Method for Antibabesial Drug Screening  

PubMed Central

In vitro evaluation of chemotherapeutic agents against Babesia and Theileria parasites has become routine, and the effectiveness of these chemicals is usually determined by comparing the parasitemia dynamics of untreated and treated parasites. Although microscopy is widely used to calculate parasitemia, several disadvantages are associated with this technique. The present study evaluated a fluorescence-based method using SYBR green I stain (SG I) to screen antibabesial agents in in vitro cultures of Babesia bovis. The linearity between relative fluorescence units (RFU) and parasitemia was found to be well correlated with a 0.9944 goodness-of-fit (r2) value. Subsequently, 50% inhibitory concentration (IC50) values were calculated for 3 antiprotozoan agents, diminazene aceturate, nimbolide, and gedunin, by this method. For diminazene aceturate and nimbolide, the IC50s determined by the fluorescence-based method (408 nM and 8.13 ?M, respectively) and microscopy (400.3 nM and 9.4 ?M, respectively) were in agreement. Furthermore, the IC50 of gedunin determined by the fluorescence-based method (19 ?M) was similar to the recently described microscopy-based value (21.7 ?M) for B. bovis. Additionally, the Z? factor (0.80 to 0.90), signal-to-noise (S/N) ratio (44.15 to 87.64), coefficient of variation at the maximum signal (%CVmax) (0.50 to 2.85), and coefficient of variation at the minimum signal (%CVmin) (1.23 to 2.21) calculated for the fluorescence method using diminazene aceturate were comparable to those previously determined in malaria research for this assay. These findings suggest that the fluorescence-based method might be useful for antibabesial drug screening and may have potential to be developed into a high-throughput screening (HTS) assay. PMID:24914124

Guswanto, Azirwan; Sivakumar, Thillaiampalam; Rizk, Mohamed Abdo; Elsayed, Shimaa Abd Elsalam; Youssef, Mohamed Ahmed; ElSaid, ElSaid El Shirbini; Yokoyama, Naoaki

2014-01-01

262

Conditionally fluorescent molecular probes for detecting single base changes in  

E-print Network

base changes) between otherwise identical nucleic acid sequences can have important biological and quantitation of nucleic acid sequences with single base resolution are important research goals with vast, dissociate slowly) and practically prevent the intended hybridization reactions. To achieve single-base

Zhang, David Yu

263

DNA methyltransferase activity detection based on fluorescent silver nanocluster hairpin-shaped DNA probe with 5'-C-rich/G-rich-3' tails.  

PubMed

DNA methylation has received a large amount of attention due to its close relationship to a wide range of biological phenomena, such as gene activation, gene imprinting, and chromatin stability. Herein, we have designed a hairpin-shaped DNA probe with 5'-C-rich/G-rich-3' tails and developed a simple and reliable fluorescence turn-off assay for DNA adenine methylation (Dam) methyltransferase (MTase) detection combining site recognition and the fluorescence enhancement of DNA-templated silver nanoclusters (DNA-AgNCs) by guanine-rich DNA sequences. A designed hairpin probe with 5' CCCTTACCCC and 3' GGGTGGGGTGGGGTGGGG displays a bright red emission after reacting with AgNO3 and NaBH4. In the presence of Dam MTase, the methylation-sensitive restriction endonuclease Dpn I which has the same recognition site with the Dam MTase can split the probe, freeing the G-rich sequence from the C-rich sequence, thus quenching the fluorescence of DNA-AgNCs. Compared to traditional fluorescent-based methods, this strategy is simple and inexpensive. A linear response to concentrations of Dam MTase which range from 1U/mL to 100U/mL and a detection limit of 1U/mL are obtained without any amplification steps. In addition, we also demonstrate the method can be used for evaluation and screening of inhibitors for Dam MTase. PMID:25682501

Liu, Wenting; Lai, Han; Huang, Rong; Zhao, Chuntao; Wang, Yimo; Weng, Xiaocheng; Zhou, Xiang

2015-06-15

264

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

PubMed

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

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

2015-02-01

265

A simple and highly selective 2,2-diferrocenylpropane-based multi-channel ion pair receptor for Pb(2+) and HSO4(.).  

PubMed

A structurally simple, 2,2-diferrocenylpropane-based ion pair receptor was synthesized and characterized by (1)H NMR, (13)C NMR, HRMS, elemental analyses, and single-crystal X-ray diffraction. The ion pair receptor showed excellent selectivity and sensitivity towards Pb(2+) with multi-channel responses: a fluorescence enhancement (more than 42-fold), a notable color change from yellow to red, redox anodic shift (?E1/2 = 151 mV), while HSO4(-) promoted fluorescence enhancement when Pb(2+) or Zn(2+) was bonded to the cation binding-site. (1)H NMR titration and density functional theory were performed to reveal the sensing mechanism based on photo-induced electron transfer (PET). PMID:25715317

Wan, Qian; Zhuo, Ji-Bin; Wang, Xiao-Xue; Lin, Cai-Xia; Yuan, Yao-Feng

2015-03-10

266

Conventional and photonic crystal fiber based two-photon fluorescence biosensing  

NASA Astrophysics Data System (ADS)

Optical fiber probes are widely used in the biomedical field for applications such as optical microscopy, endoscopy, and optical biopsy. Due to their flexibility and small size, optical fibers offer a minimally invasive light interface for imaging and spectroscopic analysis of internal tissue. The development of fluorescent probes for studies of biological processes has increased the importance of developing optical methods for quantitative, in vivo diagnosis. In this dissertation, we discuss the development of a novel two-photon optical fiber fluorescence (TPOFF) probe for real time, in vivo, quantitative fluorescence measurements in biological samples. In order to understand and optimize two-photon excitation through an optical fiber, pulse propagation effects must be considered. We found a simple phenomenological scaling behavior for the energy dependence of the pulse width for negatively pre-chirped pulses propagating in a normally dispersive fiber. As a consequence of this scaling behavior, the dependence of two-photon fluorescence (TPF) on the pulse intensity becomes sub-quadratic. The TPOFF probe employs a scheme where the same single-mode fiber (SMF) is used for both the excitation and collection of TPF. Using this fiber probe, we show quantification of tumor fluorescence both ex vivo and in vivo. In ex vivo measurements of tumors developed from cells expressing the green fluorescence protein (GFP), the TPOFF probe detected fluorescence from tumors with as little as 0.3% GFP cells. These results were similar to flow cytometry analysis of isolated cells from the tumors. The TPOFF measurements of GFP tumors in live, anesthetized mice showed a linear relationship between the measured fluorescence and the percentage of GFP expressing cells. The TPOFF probe was also used in targeted binding experiments of Herceptin antibody and folic acid-dendrimer nanoparticle conjugates. To improve the sensitivity of the TPOFF probe, a double-clad photonic crystal fiber (DCF) was employed. This fiber combines the advantages of both single mode fibers (high excitation efficiencies) and multimode fibers (high collection efficiencies). When we compare the through-fiber TPF signal from a Rhodamine dye gel collected by an SMF and DCF, we observe over an order of magnitude signal enhancement.

Myaing, Mon Thiri

267

Simple plant-based design strategies for volatile organic pollutants  

SciTech Connect

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

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

1999-12-31

268

Time resolved laser induced fluorescence measurements: Considerations when using Nd:YAG based system  

NASA Astrophysics Data System (ADS)

Time-resolved laser-induced fluorescence (TR-LIF) and the laser induced breakdown spectroscopy (LIBS) have been shown to be methods which are fast and sensitive to provide information about the constituents in analyzed samples. TR-LIF and LIBS have similar hardware requirements. In this paper, we analyze some characteristics of TR-LIF/LIBS system implemented in our laboratory, considering the fact that the excitation part of the system is based on Nd:YAG laser and Optical Parametric Oscillator (OPO). The laser is more than powerful enough (365 mJ at 1064 nm, variable OPO output >5 mJ) for LIBS, but somehow slow (the length of fundamental laser harmonic output pulse is about 5 ns) for fluorescence measurements in our present area of interest, namely plants and food products. Fortunately, the pulse length of tunable OPO output (320-475 nm) is less then 1 ns, so by means of a correct deconvolution procedure it is possible to measure the fluorescence lifetimes in the range as small as a few nanoseconds. The fluorescence detection part of our system is based on picosecond streak camera. Using the fluorescent dyes (Rhodamine B and Fluorescein) ethanol solutions we verified the analyzing capabilities of our TR-LIF system.

Rabasovic, Maja S.; Sevic, Dragutin; Terzic, Mira; Marinkovic, Bratislav P.

2012-05-01

269

Hybridization chain reaction-based fluorescence immunoassay using DNA intercalating dye for signal readout.  

PubMed

A novel format of fluorescence immunosorbent assay based on the hybridization chain reaction (HCR) using a DNA intercalating dye for signal readout was constructed for the sensitive detection of targets, both in competitive and sandwich modes. In this platform, the capture and recognition processes are based on immunoreactions and the signal amplification depends on the enzyme-free, isothermal HCR-induced labelling event. After a competitive or a sandwich immunoreaction, a biotinylated capture DNA was bound to a biotinylated signal antibody through avidin, and triggered the HCR by two specific hairpins into a nicked double helix. Gene Finder (GF), a fluorescent probe for double-strand DNA, was intercalated in situ into the amplified chain to produce the fluorescence signal. The limit of detection (LOD) for rabbit IgG in competitive mode by HCR/GF immunoassay was improved at least 100-fold compared with the traditional fluorescence immunoassay using the fluorescein isothiocyanate-labelled-streptavidin or fluorescein isothiocyanate-labelled second antibody as the signal readout. The proposed fluorescence immunoassay was also demonstrated by using ?-fetoprotein as the model target in sandwich mode, and showed a wide linear range from 28 ng mL(-1) to 20 ?g mL(-1) with a LOD of 6.0 ng mL(-1). This method also showed satisfactory analysis in spiked human serum, which suggested that it might have great potential for versatile applications in life science and point-of-care diagnostics. PMID:24828400

Deng, Yan; Nie, Ji; Zhang, Xiao-hui; Zhao, Ming-Zhe; Zhou, Ying-Lin; Zhang, Xin-Xiang

2014-07-01

270

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

271

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

PubMed Central

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

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

2015-01-01

272

An ultra-high sensitive platform for fluorescence detection of micrococcal nuclease based on graphene oxide.  

PubMed

Micrococcal nuclease (MNase) is the extracellular nuclease of Staphylococcus aureus (S. aureus). It preferentially digests single-stranded nucleic acids. The existence of MNase can be the standard to identify S. aureus and the content of MNase can be used to evaluate the pathogenicity of S. aureus. Herein, an ultra-high sensitive and selective fluorescent sensing platform for MNase is developed based on MNase-induced DNA strand scission and the difference in affinity of graphene oxide (GO) for single-stranded DNA containing different numbers of bases in length. In the absence of MNase, the adsorption of the dye-labeled ssDNA on GO makes the dyes close proximity to GO surface resulting in high efficiency quenching of fluorescence of the dyes. Conversely, and very importantly, in the presence of MNase, it cleaves the dye-labeled ssDNA into small fragments. The introduction of GO into the sensing solution results in weak quenching of the fluorescence of the dyes due to the weak affinity of the short dye-labeled oligonuleotide fragment to GO, and the fluorescence intensity gradually increases with increasing concentration of MNase. MNase can be detected in a range of 8×10?? to 1.6×10?³ unit/mL with a detection limit of 2.7×10?? unit/mL and good selectivity. The detection limit is of two orders of magnitude lower than those reported fluorescence MNase assays. Moreover, when the GO-based biosensor is used in S. aureus sample assays, preeminent fluorescence signals are obtained, thus the platform of the GO-based biosensor can be used to detect MNase in real-world samples. PMID:23238320

He, Yue; Xiong, Ling-Hong; Xing, Xiao-Jing; Tang, Hong-Wu; Pang, Dai-Wen

2013-04-15

273

Ultrasensitive detection of microRNAs based on hairpin fluorescence probe assisted isothermal amplification.  

PubMed

A hairpin fluorescence probe assisted isothermal amplification strategy was used for microRNAs (miRNAs) detection. The fluorescence hairpin probe was rationally designed by software NUPACK to reduce background signal. This isothermal amplification method consisted of two circuits. The amplification strategy not only could detect miRNA, but also amplified and reversely transcribed miRNA into DNA to enhance the stability of the target. The approach was ultrasensitive and as low as 8.5×10(-15)mol/L miR-Let-7a, corresponding to 8.5×10(-20)mol miR-Let-7a in 10µL, was able to be detected within 20min at 37°C. Moreover, successful detection of miR-Let-7a in a total RNA sample was also achieved. Thus, the rapid, simple, isothermal, and highly sensitive approach should be a promising tool for on-the-spot detection. PMID:24613970

Ma, Cuiping; Liu, Sen; Shi, Chao

2014-08-15

274

Simple Fibroblast-Based Assay for Screening of New Antimicrobial Drugs against Mycobacterium tuberculosis  

Microsoft Academic Search

In this study, we propose a simple and reproducible host-cell-based assay for the screening of antimyco- bacterial drugs that is suitable for drug discovery. The method evaluates both antimycobacterial activity of the drugs and their cytotoxicity to host cells. The basis of this simple fibroblast-based assay (SFA) is that cells of human lung fibroblast cell line MRC-5, which are highly

Takemasa Takii; Yoshifumi Yamamoto; Taku Chiba; Chiyoji Abe; John T. Belisle; Patrick J. Brennan; Kikuo Onozaki

2002-01-01

275

Improving Pb 2+ detection using DNAzyme-based fluorescence sensors by pairing fluorescence donors with gold nanoparticles  

Microsoft Academic Search

For previously reported fluorescence Pb2+ sensors, DNAzymes have lead to a significant increase in Pb2+ detecting sensitivity and specificity. However, these sensors suffer from incomplete fluorescence quenching and require additional steps for annealing DNAzymes and substrates as well as for removing the uncoupled substrates. In this study, we successfully overcome these issues by immobilizing the substrate nucleic acids on gold

Joong Hyun Kim; Sang Ho Han; Bong Hyun Chung

2011-01-01

276

Clinical performance of two fluorescence-based methods in detecting occlusal caries lesions in primary teeth.  

PubMed

This in vivo study aimed to evaluate the performance of 2 fluorescence-based methods in detecting occlusal caries lesions in primary teeth, compared with the performance of visual inspection and radiographic methods, and to propose a mathematic correction of the diagnostic parameters due to the imperfect reference standard method used in the study. Two examiners assessed the occlusal surfaces of 407 primary teeth (62 children) using visual inspection (ICDAS), radiographic, DIAGNOdent pen (pen type laser fluorescence; LFpen), and fluorescence camera (FC) methods. At the noncavitated threshold (NC) the reference standard method was the results of ICDAS, and at the dentine caries threshold (D3) teeth diagnosed with dentine caries by ICDAS or radiographic methods were subjected to operative treatment to confirm the presence of lesion. Reproducibility, sensitivity, specificity, accuracy, and the area under the ROC curve were calculated for the methods at both thresholds. At the NC threshold, LFpen had a slightly better performance compared to the FC and radiographic methods. However, at the D3 threshold, both fluorescence-based methods performed similarly. Visual inspection and radiographic methods presented higher specificities but lower sensitivities than fluorescence methods. After corrections, there was a significant decrease in some parameters. In conclusion, both fluorescence-based methods presented similar performance in detecting occlusal dentine caries lesions in primary teeth, but they usually gave more false-positive results than did the visual and radiographic methods. The correction proposed shows that the performance of the methods can be overestimated, and the correction should be validated and considered in further studies that use an imprecise reference standard method. PMID:21625126

Matos, R; Novaes, T F; Braga, M M; Siqueira, W L; Duarte, D A; Mendes, F M

2011-01-01

277

Abstract--Password-based authentication schemes are convenient, but vulnerable to simple dictionary attacks.  

E-print Network

enhanced biometric-based user authentication scheme for the C/S System. I. INTRODUCTION Remote identity proposed the security improved biometric-based user authentication scheme for C/S system than Das's scheme Abstract-- Password-based authentication schemes are convenient, but vulnerable to simple

278

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

E-print Network

Simple 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. The main prac- tical benefit of identity-based cryptography is in greatly reducing the need for

Ding, Xuhua

279

Pedagogical Functions of Simple Web-Discussion During Work-Based Learning Periods in Vocational Education.  

ERIC Educational Resources Information Center

The pedagogical functions of simple World Wide Web-based discussions during work-based learning periods in vocational education were examined in a study of a secondary-level work-based practical nursing program in Finland. The students (age range, 16 to 43 years) participated in 17 Web discussion groups during their 120-week practical nursing…

Mahlamaki-Kultanen, Seija; Hulkari, Kirsti

280

Hyper-spectral modulation fluorescent imaging using double acousto-optical tunable filter based on TeO2-crystals  

NASA Astrophysics Data System (ADS)

We have proposed a method for hyper-spectral fluorescent imaging based on acousto-optical filtering. The object of interest was pumped using ultraviolet radiation of mercury lamp equipped with monochromatic excitation filter with the window of transparency centered at 365 nm. Double TeO2-based acousto-optical filter, tunable in range from 430 to 780 nm and having 2 nm bandwidth of spectral transparency, was used in order to detect quasimonochromatic images of object fluorescence. Modulating of ultraviolet pump intensity was used in order to reduce an impact of non-fluorescent background on the sample fluorescent imaging. The technique for signal-to-noise ratio improvement, based on fluorescence intensity estimation via digital processing of modulated video sequence of fluorescent object, was introduced. We have implemented the proposed technique for the test sample studying and we have discussed its possible applications.

Zaytsev, Kirill I.; Perchik, Alexey V.; Chernomyrdin, Nikita V.; Kudrin, Konstantin G.; Reshetov, Igor V.; Yurchenko, Stanislav O.

2015-01-01

281

A smart-lighting emergency ballast for fluorescent lamps based on microcontroller  

Microsoft Academic Search

A new emergency ballast for fluorescent lamps is presented. The fundamental block is the control circuit based on a microcontroller that performs the supervision and control function, achieving an increase in the installation security. High frequency electronics techniques are proposed for the battery charger and the lamp driver, with high power factor in the first and high luminous efficacy in

J. M. Alonso; J. Diaz; C. Blanco; M. Rico

1993-01-01

282

Patch-Based Markov Models for Event Detection in Fluorescence Bioimaging  

E-print Network

the live states of the matter. Original image analysis methods are then required to process challenging 2D or 3D image sequences. Recently, tracking methods that estimate the whole trajectories of movingPatch-Based Markov Models for Event Detection in Fluorescence Bioimaging Thierry P´ecot1

Paris-Sud XI, Université de

283

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

E-print Network

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

284

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

285

Fluorescence intensity, lifetime, and anisotropy screening of living cells based on total internal reflection techniques  

Microsoft Academic Search

A setup for fluorescence measurements of surfaces of biological samples, in particular the plasma membrane of living cells, is described. The method is based on splitting of a laser beam and multiple total internal reflections (TIR) within the bottom of a microtiter plate, such that up to 96 individual samples are illuminated simultaneously by an evanescent electromagnetic field. Two different

Thomas Bruns; Brigitte Angres; Heiko Steuer; Wolfgang S. L. Strauss; Herbert Schneckenburger

2009-01-01

286

Mismatch Base Pair Detection by Fluorescence Spectral Change Upon Addition of Metal Cation—Toward Efficient Analysis of Single Nucleotide Polymorphism  

Microsoft Academic Search

Addition of mercury (II) cation to fluorescent-labeled duplex involving a T:T mismatch base pair and silver (I) cation to fluorescent-labeled duplex involving a C:C mismatch base pair significantly changed the fluorescence intensity, but no significant change in the fluorescence intensity was observed for duplexes involving the other base pairs. The fluorescence spectral change upon addition of the metal cation can

Hidetaka Torigoe; Akira Ono; Tetsuo Kozasa

2007-01-01

287

New approach to breast tumor detection based on fluorescence x-ray analysis  

PubMed Central

A new technical approach to breast-tumor detection is proposed. The technique is based on fluorescence x-ray analysis, and can identify a miniature malignant tumor within the breast. The primary beam intensity needed in fluorescence x-ray analysis is on a lower order of magnitude than that used in mammography. Thus, the newly-proposed technique would enable detection of a still tiny breast cancer while dramatically lowering the radiation dose. Field-emission x-ray sources might be a key for translating this concept into a medical technique. PMID:20930932

Hayashi, Yasuhiko; Okuyama, Fumio

2010-01-01

288

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

NASA Astrophysics Data System (ADS)

A dissolved oxygen sensor based on ruthenium(Ru) fluorescence and U-shape plastic optical fiber (POF) was described. Dichlorotris (1, 10-phenanthroline) ruthenium (II) was used as an oxygen indicator, which was coated on to the surface of a 1mm diameter U-shaped POF. Phase modulation technique is used to measure fluorescence lifetime. The phase difference between 100% and 0% dissolved oxygen is 1.78 degree. By using the nonlinear assumption, we also calculate that the there are only 20% thickness of the sensor material is affected by DO.

Chu, Fenghong; Cai, Haiwen; Qu, Ronghui; Fang, Zujie

2007-11-01

289

A fluorescence-based method for rapid and direct determination of polybrominated diphenyl ethers in water.  

PubMed

A new method was developed for rapid and direct measurement of polybrominated diphenyl ethers (PBDEs) in aqueous samples using fluorescence spectroscopy. The fluorescence spectra of tri- to deca-BDE (BDE 28, 47, 99, 153, 190, and 209) commonly found in environment were measured at variable emission and excitation wavelengths. The results revealed that the PBDEs have distinct fluorescence spectral profiles and peak positions that can be exploited to identify these species and determine their concentrations in aqueous solutions. The detection limits as determined in deionized water spiked with PBDEs are 1.71-5.82?ng/L for BDE 28, BDE 47, BDE 190, and BDE 209 and 45.55-69.95?ng/L for BDE 99 and BDE 153. The effects of environmental variables including pH, humic substance, and groundwater chemical composition on PBDEs measurements were also investigated. These environmental variables affected fluorescence intensity, but their effect can be corrected through linear additivity and separation of spectral signal contribution. Compared with conventional GC-based analytical methods, the fluorescence spectroscopy method is more efficient as it only uses a small amount of samples (2-4?mL), avoids lengthy complicated concentration and extraction steps, and has a low detection limit of a few ng/L. PMID:25705548

Shan, Huimei; Liu, Chongxuan; Wang, Zheming; Ma, Teng; Shang, Jianying; Pan, Duoqiang

2015-01-01

290

A Fluorescence-Based Method for Rapid and Direct Determination of Polybrominated Diphenyl Ethers in Water  

PubMed Central

A new method was developed for rapid and direct measurement of polybrominated diphenyl ethers (PBDEs) in aqueous samples using fluorescence spectroscopy. The fluorescence spectra of tri- to deca-BDE (BDE 28, 47, 99, 153, 190, and 209) commonly found in environment were measured at variable emission and excitation wavelengths. The results revealed that the PBDEs have distinct fluorescence spectral profiles and peak positions that can be exploited to identify these species and determine their concentrations in aqueous solutions. The detection limits as determined in deionized water spiked with PBDEs are 1.71–5.82?ng/L for BDE 28, BDE 47, BDE 190, and BDE 209 and 45.55–69.95?ng/L for BDE 99 and BDE 153. The effects of environmental variables including pH, humic substance, and groundwater chemical composition on PBDEs measurements were also investigated. These environmental variables affected fluorescence intensity, but their effect can be corrected through linear additivity and separation of spectral signal contribution. Compared with conventional GC-based analytical methods, the fluorescence spectroscopy method is more efficient as it only uses a small amount of samples (2–4?mL), avoids lengthy complicated concentration and extraction steps, and has a low detection limit of a few ng/L. PMID:25705548

Shan, Huimei; Ma, Teng; Shang, Jianying; Pan, Duoqiang

2015-01-01

291

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

292

Enzymatic cascade based fluorescent DNAzyme machines for the ultrasensitive detection of Cu(II) ions.  

PubMed

A novel enzymatic cascade based fluorescent DNAzyme machine has been developed for the amplified detection of copper (Cu(2+)) ions. This is the first attempt to carry out the combination of the self-cleaving DNAzyme and the polymerase/endonuclease reaction cycles involving cleaved substrate extension. In the presence of Cu(2+) ions, the enzyme strand carries out catalytic reactions to hydrolytic cleavage of the substrate strand. The cleaved DNAzyme substrates act as primers and trigger the Klenow Fragment polymerization. Nb.BbvCI endonuclease cuts the double-stranded niking site and thus opens a new site for a new replication. The replication regenerates the complete dsDNA to initiate another cycle of nicking, polymerization and displacement. Finally the fluorescence dye, SG, inserts into the DNA double helix to generate a distinguishable fluorescence enhancement. The Cu(2+) ions act as the activator for enzymatic cascade amplification generating multiple duplex structures in the nascent product. An increasing fluorescence is observed with increasing Cu(2+) ions concentration. A good nonlinear correlation (R=0.9997) was obtained between fluorescence intensity and the cubic logarithm of the Cu(2+) ions concentration over the range 0.50-200 nM. This nonlinear response phenomenon results in an efficient improvement of the sensitivity of our current proposed assay. The activation of such enzymatic cascades through analyte-DNAzyme interactions is not only valuable to activate the cooperation of enzyme networks, but also has a substantial impact on the development of amplified DNAzyme sensors. PMID:24787125

He, Jing-Lin; Zhu, Shuang-Li; Wu, Ping; Li, Pan-Pan; Li, Ting; Cao, Zhong

2014-10-15

293

Thiol reactive probe based on fluorescence resonance energy transfer between fluorescein and Au nanoparticles.  

PubMed

Sensitive and selective fluorescent probe of thiols with lower limit of detection based on fluorescence resonance energy transfer (FRET) between fluorescein and Au nanoparticles (AuNPs) is presented. The fluorescein-AuNPs complex emits weak fluorescence. Upon chemically binding to organosulfur compound that contains a carbon-bonded sulfhydryl (-C-SH or R-SH) thiols, a stable enhancement of fluorescence is observed due to the competitive binding on AuNPs between thiols and fluorescein. The magnitude of fluorescence enhancement is linearly proportional to the logarithm of the thiols concentration. We use cysteine as an example to show how this useful analytical assay works selectively, which is closely nonresponsive to 20 other amino acids even though they are in solution at a concentration 10 times greater than the thiols. The detection limit for cysteine is 7.27 × 10-9 mol L-1. The possible mechanism of this assay is discussed in details. The proposed method was successfully applied for the determination of Cys in urine. PMID:24664329

Qi, Li; Song, Juan; Wu, Fang-Ying; Wan, Yi-Qun

2014-01-01

294

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

295

Detection of DNA hybridization based on SnO2 nanomaterial enhanced fluorescence  

NASA Astrophysics Data System (ADS)

In this paper, enhanced fluorescence emissions were firstly investigated based on SnO2 nanomaterial, and its application in the detection of DNA hybridization was also demonstrated. The microarray of SnO2 nanomaterial was fabricated by the vapour phase transport method catalyzed by patterned Au nanoparticles on a silicon substrate. A probe DNA was immobilized on the substrate with patterned SnO2 nanomaterial, respectively, by covalent and non-covalent linking schemes. When a fluorophore labelled target DNA was hybridized with a probe DNA on the substrate, fluorescence emissions were only observed on the surface of SnO2 nanomaterial, which indicated the property of enhancing fluorescence signals from the SnO2 nanomaterial. By comparing the different fluorescence images from covalent and non-covalent linking schemes, the covalent method was confirmed to be more effective for immobilizing a probe DNA. With the combined use of SnO2 nanomaterial and the covalent linking scheme, the target DNA could be detected at a very low concentration of 10 fM. And the stability of SnO2 nanomaterial under the experimental conditions was also compared with silicon nanowires. The findings strongly suggested that SnO2 nanomaterial could be extensively applied in detections of biological samples with enhancing fluorescence property and high stability.

Gu, Cuiping; Huang, Jiarui; Ni, Ning; Li, Minqiang; Liu, Jinhuai

2008-09-01

296

A FRET-Based Ratiometric Chemosensor for in Vitro Cellular Fluorescence Analyses of pH  

PubMed Central

Ratiometric fluorescence sensing is an important technique for precise and quantitative analysis of biological events occurring under complex conditions by simultaneously recording fluorescence intensities at two wavelengths and calculating their ratios. Herein, we design a ratiometric chemosensor for pH that is based on photo-induced electron transfer (PET) and binding-induced modulation of fluorescence resonance energy transfer (FRET) mechanisms. This ratiometric chemosensor was constructed by introduction of a pH-insensitive coumarin fluorophore as a FRET donor into a pH-sensitive amino-naphthalimide derivative as the FRET acceptor. The sensor exhibited clear dual-mission signal changes in blue and green spectral windows upon pH changes. The pH sensor was applied for not only measuring cellular pH, but also for visualizing stimulus-responsive changes of intracellular pH values. PMID:21982292

Zhou, Xianfeng; Su, Fengyu; Lu, Hongguang; Senechal-Willis, Patti; Tian, Yanqing; Johnson, Roger H.; Meldrum, Deirdre R.

2011-01-01

297

DNA-length-dependent fluorescent sensing based on energy transfer in self-assembled multilayers.  

PubMed

In this paper, a novel DNA-length-dependent fluorescent sensor was constructed based on the fluorescence resonance energy transfer. In the self-assembled multilayers (Quartz/GO/PDDA/Tx-DNA/PDDA/ZnO@CdS), ZnO@CdS and graphene oxide(GO) were employed as an energy donor and an energy acceptor, respectively. Single-stranded Tx-DNA (x represents different chain length of DNA) and poly(diallydimethylammonium) chloride (PDDA) were used as a linker. In the presence of complementary Px-DNA, the formation of double-stranded DNA leads to a change in chain length and achieves the purpose of changing the distance between ZnO@CdS and GO. Thereby, it enhances the efficiency of energy transfer between ZnO@CdS and GO resulting in the quench of fluorescence of ZnO@CdS, and thus different length DNA sequence was detected. PMID:24934748

Sun, Xiang-Ying; Liu, Bin; Sun, Yan-Feng; Yu, Yaming

2014-11-15

298

Laser-induced fluorescent micro-structures in silver nanoparticle based films  

NASA Astrophysics Data System (ADS)

An optical method for the formation of micron sized line features within silver nanoparticle based films using focused laser irradiation is developed. The observed light-induced effect is a strong function of light flux producing line features with widths of less than 5 ?m, which can be controlled by careful selection of the focused incident beam waist. A potentially useful local feature is generated just outside the region of laser exposure; the film displays significant fluorescence emission across the visible spectrum. The source of the fluorescence is attributed to the presence of hydrated citrate salts that have been decomposed due to local heating and recrystallized as confirmed by electron microscopy and confocal fluorescence spectroscopy.

Kandpal, Sanjeev Kumar; Co, Aimee; Allcroft, Kody; Neivandt, David J.; Bousfield, Douglas W.; Mason, Michael D.

2014-03-01

299

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

300

Rapid High-Throughput Assessment of Aerobic Bacteria in Complex Samples by Fluorescence-Based Oxygen Respirometry  

PubMed Central

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

O'Mahony, Fiach C.; Papkovsky, Dmitri B.

2006-01-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

302

A fluorescence detection of D-penicillamine based on Cu(2+)-induced fluorescence quenching system of protein-stabilized gold nanoclusters.  

PubMed

In this contribution, a luminescent gold nanoclusters which were synthesized by bovine serum albumin as novel fluorescent probes were successfully utilized for the determination of D-penicillamine for the first time. Cupric ion was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of D-penicillamine caused obvious restoration of fluorescence intensity of the Cu(2+)-gold nanoclusters system. Under optimum conditions, the increment in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by D-penicillamine was linearly proportional to the concentration of D-penicillamine in the range of 2.0×10(-5)-2.39×10(-4) M. The detection limit for D-penicillamine was 5.4×10(-6) M. With the off-on fluorescence signal at 650 nm approaching the near-infrared region, the present sensor for D-penicillamine detection had high sensitivity and low spectral interference. Furthermore, the novel gold nanoclusters-based fluorescent sensor has been applied to the determination of D-penicillamine in real biological samples with satisfactory results. PMID:25064503

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

2015-01-25

303

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. PMID:25426316

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

304

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

PubMed

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. PMID:25426316

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

2014-11-01

305

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

306

A turn-on coordination nanoparticle-based fluorescent probe for phosphate in human serum  

NASA Astrophysics Data System (ADS)

Coordination nanoparticles (CNPs) are becoming attractive platforms for chemical sensing applications because their unique adjustable properties offer the opportunity to design various luminescent nanoprobes. Here, we present a CNP-based fluorescent nanoprobe, in which fluorophores (rhodamine B, RB) and quenchers (methylene blue, MB) were spontaneously enfolded by coordination networks self-assembled of adenine, biphenyl-4,4'-dicarboxylic acid (BDA) and zinc ions. The aggregation of fluorophores and quenchers in CNPs resulted in a quenched state fluorescence of RB. RB and MB could be released from CNPs in the presence of phosphate, which triggered the fluorescence of RB. On the basis of recognition-driven disassembly principle, a novel turn-on fluorescent probe for the determination of PO43- with a wide response range (0.5-50 ?M) has been successfully applied in the detection of phosphate in human serum samples. This work not only develops a probe for phosphate but also provides a general strategy for designing nanoprobes or nanocarriers towards various targets by altering organic linkers or metal ions.Coordination nanoparticles (CNPs) are becoming attractive platforms for chemical sensing applications because their unique adjustable properties offer the opportunity to design various luminescent nanoprobes. Here, we present a CNP-based fluorescent nanoprobe, in which fluorophores (rhodamine B, RB) and quenchers (methylene blue, MB) were spontaneously enfolded by coordination networks self-assembled of adenine, biphenyl-4,4'-dicarboxylic acid (BDA) and zinc ions. The aggregation of fluorophores and quenchers in CNPs resulted in a quenched state fluorescence of RB. RB and MB could be released from CNPs in the presence of phosphate, which triggered the fluorescence of RB. On the basis of recognition-driven disassembly principle, a novel turn-on fluorescent probe for the determination of PO43- with a wide response range (0.5-50 ?M) has been successfully applied in the detection of phosphate in human serum samples. This work not only develops a probe for phosphate but also provides a general strategy for designing nanoprobes or nanocarriers towards various targets by altering organic linkers or metal ions. Electronic supplementary information (ESI) available: Supplementary figures. See DOI: 10.1039/c5nr00515a

Lin, Na; Li, Jian; Lu, Zhixiang; Bian, Longchun; Zheng, Liyan; Cao, Qiue; Ding, Zhongtao

2015-03-01

307

Compact flashlamp-based fluorescence imager for use under ambient-light conditions  

NASA Astrophysics Data System (ADS)

A low-power, lightweight, multiwavelength fluorescence imager based on the use of a compact xenon flashlamp, bandpass filters, gated charge-coupled device camera, and digital image processing was developed for use on an autonomous rover vehicle. The imager discriminates against ambient light by use of microsecond excitation pulses along with synchronized camera operation to limit the time period in which ambient-light photocounts are accumulated, and digital image subtraction to remove background counts. In a 10 cm square field of view, weak fluorescence, equivalent to 0.05pmol fluorescein/mm2, can be quantified against a white-light background equivalent to shaded sunlight. For application in autonomous search for organisms in extreme environments such as in situ desert rock or soil, the instrument was equipped with a set of fluorescence excitation filters (380, 450, 545, and 600nm) and emission filters (460, 510, 620, and 740nm) suitable for detection of chlorophyll, applied stains for protein, DNA, lipid and carbohydrate, and autofluorescence. True-color images were obtained through red-green-blue imaging filters (630, 535, and 470nm) used with white-light flashes. Automated focusing on ground features was based on the R-band image and was carried out prior to fluorescence image acquisition.

Lanni, Frederick; Pane, David A.; Weinstein, Shmuel J.; Waggoner, Alan S.

2007-03-01

308

Nonlinear emission of quinolizinium-based dyes with application in fluorescence lifetime imaging.  

PubMed

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

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

2015-03-19

309

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

PubMed

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

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

2014-05-15

310

Image overlay solution based on threshold detection for a compact near infrared fluorescence goggle system  

NASA Astrophysics Data System (ADS)

Near infrared (NIR) fluorescence imaging has shown great potential for various clinical procedures, including intraoperative image guidance. However, existing NIR fluorescence imaging systems either have a large footprint or are handheld, which limits their usage in intraoperative applications. We present a compact NIR fluorescence imaging system (NFIS) with an image overlay solution based on threshold detection, which can be easily integrated with a goggle display system for intraoperative guidance. The proposed NFIS achieves compactness, light weight, hands-free operation, high-precision superimposition, and a real-time frame rate. In addition, the miniature and ultra-lightweight light-emitting diode tracking pod is easy to incorporate with NIR fluorescence imaging. Based on experimental evaluation, the proposed NFIS solution has a lower detection limit of 25 nM of indocyanine green at 27 fps and realizes a highly precise image overlay of NIR and visible images of mice in vivo. The overlay error is limited within a 2-mm scale at a 65-cm working distance, which is highly reliable for clinical study and surgical use.

Gao, Shengkui; Mondal, Suman B.; Zhu, Nan; Liang, RongGuang; Achilefu, Samuel; Gruev, Viktor

2015-01-01

311

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

312

Design of a simple high-power-factor rectifier based on the flyback converter  

Microsoft Academic Search

An equivalent circuit model for the discontinuous conduction mode flyback converter based on the loss-free resistor concept is presented. This simple model correctly describes the basic power processing properties of the converter, including input port resistor emulation, output port power source characteristics, and control characteristics. Based on this model, steady-state design equations are described and are used in a design

Robert Erickson; Michael Madigan; Sigmund Singer

1990-01-01

313

Infection on a chip: a microscale platform for simple and sensitive cell-based virus assays  

E-print Network

responses to minimize the spread of viral diseases. While nucleic acid- based assays have dominated newInfection on a chip: a microscale platform for simple and sensitive cell-based virus assays Ying sensitivity, uses excessive reagents, and is hard to automate. Recent modification of the assay to exploit

Beebe, David J.

314

A Simple System Providing Location-Based Service on Urban Area  

Microsoft Academic Search

This paper proposes a simple location-based service which can be used to learn places people visit in their everyday lives. Unlike the similar services provided by mobile operators which typically use trilateration calculation to derive location from multiple based stations, our proposal relies on a location server to store the location information of subscribed users. Therefore, it can be easily

Kin-Yeung WONG; Yiu-Man CHOI

315

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

PubMed

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

Martinc, Boštjan; Vovk, Tomaž

2013-01-01

316

Development of a competitive fluorescence-based synaptosome binding assay for brevetoxins  

PubMed Central

Brevetoxins are a family of ladder-frame polyether toxins produced during blooms of the marine dinoflagellate Karenia brevis. Inhalation of brevetoxins aerosolized by wind and wave action can lead to asthma-like symptoms in beach goers. Consumption of either shellfish or finfish exposed to K. brevis blooms can lead to the development of neurotoxic shellfish poisoning. The toxic effects of brevetoxins are due to activation of voltage-sensitive sodium channels (VSSCs) in cell membranes. Binding of brevetoxin analogs and competitors to site 5 on these channels has historically been measured using a radioligand competition assay that is fraught with difficulty, including slow analysis time, production of radioactive waste, and cumbersome and expensive methods associated with the generation of radioactive labeled ligands. In this study, we describe the development of a novel fluorescent synaptosome binding assay for the brevetoxin receptor. BODIPY®-conjugated to PbTx-2 was used as the labeled ligand. The BODIPY®-PbTx-2 conjugate was found to displace [3H]-PbTx-3 from its binding site on VSSCs on rat brain synaptosomes with an equilibrium inhibition constant of 0.11 nM. We have shown that brevetoxin A and B analogs are all able to compete for binding with the fluorescent ligand. Most importantly, this assay was validated against the current site 5 receptor binding assay standard, the radioligand receptor assay for the brevetoxin receptor using [3H]-PbTx-3 as the labeled ligand. The fluorescence based assay yielded equilibrium inhibition constants comparable to the radioligand assay for all brevetoxin analogs. The fluorescence based assay was quicker, far less expensive, and did not generate radioactive waste or need radioactive facilities. As such, this fluorescence-based assay can be used to replace the current radioligand assay for site 5 on voltage-sensitive sodium channels and will be a vital tool for future experiments examining the binding affinity of various ligands for site 5 on sodium channels. PMID:22984362

McCall, Jennifer R.; Jacocks, Henry M.; Baden, Daniel G.; Bourdelais, Andrea J.

2012-01-01

317

Using quantum mechanics to investigate the photophysical properties of the DNA and RNA bases and their fluorescent analogs  

NASA Astrophysics Data System (ADS)

The ability of the nucleic acids to absorb ultraviolet light and remain relatively photostable is a property upon which life depends. The nucleobases, which are the primary chromophores, when irradiated display rapid radiationless decay back to the ground state, in general faster than is needed for photoreaction. Fluorescent analogs of these bases have structures similar to the nucleic acid bases, but display much longer excited state lifetimes. Theoretical investigations using quantum mechanical methods can provide insight into the precise mechanisms of these decay processes, and to the molecular specifics that contribute to them. The results of multi-reference configuration interaction (MRCI) ab initio investigations into these mechanisms are presented, with emphasis on cytosine and its fluorescent analog 5-methyl-2-pyrimidinone (5M2P). A comprehensive picture of the potential energy surfaces of these two bases is given, including stationary points and conical intersections, where radiationless transisitons are promoted, between up to three state surfaces, as well as pathways connecting these points for each base. Cytosine is shown to have two different energetically accessible radiationless decay channels. The fluorescence of 5M2P is also demonstrated theoretically, with mechanism proposed. The potential energy surfaces of the two bases have many close similarities, with the different photophysical properties being attributed to subtle energetic differences between the two bases. Nonadiabatic coupling and the geometric phase effect are analyzed in detail near conical intersections in cytosine, including in a region close to a three-state conical intersection. A substituent effect study on the 2-pyrimidinone ring system shows that the presence, position and orientation of the amino group in cytosine is central to its photophysical properties, particulary its high absorption energy, and can be explained with a simple Frontier Molecular Orbital model. The effects of water solvent on the excitation energies of cytosine and uracil are theoretically investigated using two multi-reference ab initio methods, a quantum mechanical molecular mechanics method using MRCI (MRCI-QM/MM), and the fragment molecular orbital multiconfiguration self-consistent field method (FMO-MCSCF). The solvatochromic shifts calculated from both methods agree well with other more expensive methods and experimental data. The effects of water on the photophysical pathways of cytosine is also investigated using MRCI-QM/MM, including considerations of solvent reorganization. Results show that the overall effect of water on the decay mechanisms is small, with neither decay channel being significantly blocked or favored.

Kistler, Kurt A.

318

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

NASA Astrophysics Data System (ADS)

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 a 12,000-fold excess of a target that contains 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 Escherichia coli rpoB gene. That our probes are constructed from multiple oligonucleotides circumvents synthesis limitations and enables long continuous DNA sequences to be probed.

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

2013-09-01

319

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

PubMed

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

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

2015-02-15

320

A new fluorescent chemosensor for Al3+ ion based on schiff base naphthalene derivatives  

NASA Astrophysics Data System (ADS)

A new naphthalene derivative receptor (H2L) was synthesized. The chemosensor (H2L) exhibited a strong fluorescence enhancement in the presence of trace amounts of Al3+, attributable to chelation-enhanced fluorescence (CHEF) effect, which also displayed high selectivity over a series of other metal cations (Na+, K+, Cs+, Mg2+, Ba2+, Pb2+, Cr3+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+) in ethanol.

Azadbakht, Reza; Rashidi, Somaye

2014-06-01

321

pH-responsive biocompatible fluorescent polymer nanoparticles based on phenylboronic acid for intracellular imaging and drug delivery  

NASA Astrophysics Data System (ADS)

To address current medical challenges, there is an urgent need to develop drug delivery systems with multiple functions, such as simultaneous stimuli-responsive drug release and real-time imaging. Biocompatible polymers have great potential for constructing smart multifunctional drug-delivery systems through grafting with other functional ligands. More importantly, novel biocompatible polymers with intrinsic fluorescence emission can work as theranostic nanomedicines for real-time imaging and drug delivery. Herein, we developed a highly fluorescent nanoparticle based on a phenylboronic acid-modified poly(lactic acid)-poly(ethyleneimine)(PLA-PEI) copolymer loaded with doxorubicin (Dox) for intracellular imaging and pH-responsive drug delivery. The nanoparticles exhibited superior fluorescence properties, such as fluorescence stability, no blinking and excitation-dependent fluorescence behavior. The Dox-loaded fluorescent nanoparticles showed pH-responsive drug release and were more effective in suppressing the proliferation of MCF-7 cells. In addition, the biocompatible fluorescent nanoparticles could be used as a tool for intracellular imaging and drug delivery, and the process of endosomal escape was traced by real-time imaging. These pH-responsive and biocompatible fluorescent polymer nanoparticles, based on phenylboronic acid, are promising tools for intracellular imaging and drug delivery.To address current medical challenges, there is an urgent need to develop drug delivery systems with multiple functions, such as simultaneous stimuli-responsive drug release and real-time imaging. Biocompatible polymers have great potential for constructing smart multifunctional drug-delivery systems through grafting with other functional ligands. More importantly, novel biocompatible polymers with intrinsic fluorescence emission can work as theranostic nanomedicines for real-time imaging and drug delivery. Herein, we developed a highly fluorescent nanoparticle based on a phenylboronic acid-modified poly(lactic acid)-poly(ethyleneimine)(PLA-PEI) copolymer loaded with doxorubicin (Dox) for intracellular imaging and pH-responsive drug delivery. The nanoparticles exhibited superior fluorescence properties, such as fluorescence stability, no blinking and excitation-dependent fluorescence behavior. The Dox-loaded fluorescent nanoparticles showed pH-responsive drug release and were more effective in suppressing the proliferation of MCF-7 cells. In addition, the biocompatible fluorescent nanoparticles could be used as a tool for intracellular imaging and drug delivery, and the process of endosomal escape was traced by real-time imaging. These pH-responsive and biocompatible fluorescent polymer nanoparticles, based on phenylboronic acid, are promising tools for intracellular imaging and drug delivery. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04054f

Li, Shengliang; Hu, Kelei; Cao, Weipeng; Sun, Yun; Sheng, Wang; Li, Feng; Wu, Yan; Liang, Xing-Jie

2014-10-01

322

Fluorescence properties of Schiff base - N,N'-bis(salicylidene) - 1,2-Phenylenediamine in presence of bile acid host.  

PubMed

Fluorescence properties of Schiff base - N,N'-bis(salicylidene) - 1,2-phenylenediamine (LH2) is used to study the micelles formed by aggregation of different important bile acids like cholic acid, deoxycholic acid, chenodeoxycholic acid and glycocholic acid by steady state and picosecond time-resolved fluorescence spectroscopy. The fluorescence band intensity was found out to increase with concomitant red shift with gradual addition of different bile acids. Binding constant of the probe with different bile acids as well as critical micelle concentration was obtained from the variation of fluorescence intensity on increasing concentration of bile acids in the medium. The increase in fluorescence quantum yields, fluorescence decay times and substantial decrease in nonradiative decay rate constants in bile acids micellar environment points to the restricted motion of the fluorophore inside the micellar subdomains. PMID:25706604

Roy, Nayan; Paul, Pradip C; Singh, T Sanjoy

2015-05-01

323

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

324

Molecularly imprinted polymers as biomimetic receptors for fluorescence-based optical sensors  

NASA Astrophysics Data System (ADS)

Molecularly imprinted polymers (MIPs), human-made polymers capable of recognizing a particular molecule in the presence of others due to the selective cavities of the material, have been successfully applied to the development of chromatographic and solid phase extraction methods. They have also been applied to the development of electrochemical, piezoelectrical and optical sensors. In parallel with the classification of biosensors, MIP-based devices can work according to two different detection schemes: (1) affinity sensors ("plastic-bodies") and, (2) catalytic sensors ("plastic-enzymes"). In the first case the change in a characteristic optical property, most frequently fluorescence, of the analyte or of the polymer is monitored, upon their mutual interaction. Alternatively, a fluorescent analogue of the target analyte can also be used to develop sensors based on competitive assays (MIAs). Optimization of the polymer composition and, in particular, a proper choice of the nature of the functional monomers involved in the polymerization process, is critical to prepare materials able to selectively interact with the analyte in aqueous media and with the fast kinetics required for analytical applications. Moreover, a rational design of fluorescent analogues of non-naturally fluorescent templates or of fluorescent monomers able to change its property upon interaction with the analyte, is also a bottle neck for wide application of this recognition elements in optical sensing. In this paper we present several approaches to address these issues namely the optimization of MIP composition and the design and synthesis of novel fluorophores for the analysis of antibiotics and mycotoxins in real samples.

Moreno-Bondi, María C.; Urraca, Javier L.; Benito-Peña, Elena; Navarro-Villoslada, Fernando; Martins, Sofía A.; Orellana, Guillermo; Sellergren, Börje

2007-07-01

325

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

326

Continuous flow fluorescence based immunosensor for the detection of explosives and environmental pollutants  

NASA Astrophysics Data System (ADS)

A continuous flow fluorescence based immunosensor has been developed at the Naval Research Laboratory as an inexpensive, field portable device to detect environmental pollutants. Detection of environmental pollutants such as explosives [e.g. trinitrotoluene (TNT) and hexahydro-1,3,5 trinitro- 1,3,5-triazine (RDX)[ and polychlorinated biphenyls (PCBs) have been achieved at low level concentrations. The continuous flow immunosensor (CFI) employs antibodies as recognition elements for specific antigens. Antibodies specific for the environmental pollutants of interest are covalently immobilized on a solid support matrix. Subsequent saturation of the antibody-support complex with a fluorescence analog (i.e. cyanine dye) of the pollutant completes the sensor matrix. The derivatized matrix is prepacked into a micro column with a continuous flow stream of buffer that removes nonspecifically bound fluorescent analog. After a stable baseline is obtained sample injections of the desired pollutant (PCBs, TNT, RDX, etc.) into the flow stream displaces the fluorescence analog from the immobilized antibody on the solid support. A signal response over background from the displaced fluorescence analog is measured and integrated by an in-line fluorometer. Dose response curves reveal the lowest limit of detection for TNT and RDX is 20 ppb (parts-per-billion). Detection limits for PCBs is slightly higher at 1.0 ppm (part-per-million). Results from field trials conducted at two military bases, Umatilla Army Depot (Hermiston, Ore.) and Site F and A at Naval SUBASE Bangor (Bangor, Wash.) demonstrated the capabilities of the immunosensor in performing on-site field analysis in groundwater and soil leachate matrices.

Charles, Paul T.; Bart, John C.; Judd, Linda L.; Gauger, Paul R.; Ligler, Frances S.; Kusterbeck, Anne W.

1997-05-01

327

Fluorescent "turn-on" detecting CN(-) by nucleophilic addition induced Schiff-base hydrolysis.  

PubMed

A new chemosensor Sz based on Schiff-base group as recognition site and naphthalene as the fluorescence signal group was designed and synthesised. It could fluorescent "turn-on" detect cyanide (CN(-)) via a novel mechanism of nucleophilic addition induced Schiff-base hydrolysis. Adding the CN(-) into the solution of Sz could induce Sz to emit blue fluorescence at 435nm instantly. Moreover, Sz could also colorimetric detect CN(-). Upon the addition of CN(-), the Sz showed dramatic color change from yellow to colorless. These sensing procedures could not be interfered by other coexistent competitive anions such as F(-), AcO(-), H2PO4(-) and SCN(-). In addition, Sz showed high sensitivity for CN(-), the detection limits is 3.42×10(-8)M of CN(-), which is far lower than the WHO guideline of CN(-) in drinking water (less than 1.9×10(-6)M). The CN(-) test strips based on Sz could act as a convenient CN(-) test kits. PMID:25668691

Lin, Qi; Cai, Yi; Li, Qiao; Shi, Bing-Bing; Yao, Hong; Zhang, You-Ming; Wei, Tai-Bao

2015-04-15

328

Intrinsically fluorescent nanoparticles with excellent stability based on a highly crosslinked organic-inorganic hybrid polyphosphazene material.  

PubMed

A series of intrinsically fluorescent particles were synthesized, including nanoparticles with independently tunable diameters, nanotubes and microspheres, based on a highly crosslinked organic-inorganic hybrid polyphosphazene material. The nanoparticles exhibit high fluorescent intensity and excellent thermal and photobleaching stability, and can be well dispersed in both aqueous and organic media. PMID:21947021

Liu, Wei; Huang, Xiaobin; Wei, Hao; Tang, Xiaozhen; Zhu, Lu

2011-11-01

329

Ultrafast method for the analysis of fluorescence lifetime imaging microscopy data based on the Laguerre expansion technique  

Microsoft Academic Search

We report a new deconvolution method for fluorescence lifetime imaging microscopy (FLIM) based on the Laguerre expansion technique. The performance of this method was tested on synthetic and real FLIM images. The following interesting properties of this technique were demonstrated. 1) The fluorescence intensity decay can be estimated simultaneously for all pixels, without a priori assumption of the decay functional

Javier A. Jo; Qiyin Fang; Laura Marcu

2005-01-01

330

A ratiometric fluorescent nanoprobe based on terbium functionalized carbon dots for highly sensitive detection of an anthrax biomarker.  

PubMed

A ratiometric fluorescent nanoprobe based on terbium functionalized carbon dots (CDs) was designed to detect dipicolinic acid (DPA) as an anthrax biomarker with high selectivity and sensitivity. CDs were generated by one-step synthesis using an ethylenediaminetetraacetic acid precursor, and served as a scaffold for coordination with Tb(3+) and a fluorescence reference. PMID:25706307

Chen, Hao; Xie, Yujie; Kirillov, Alexander M; Liu, Liangliang; Yu, Minghui; Liu, Weisheng; Tang, Yu

2015-03-10

331

Graphene oxide-based fluorescent biosensor for protein detection via terminal protection of small-molecule-linked DNA.  

PubMed

A fluorescence method for protein detection is developed based on terminal protection of small-molecule-linked DNA by target protein and a graphene oxide-assisted DNA assay strategy. This design results in fluorescence-enhanced detection that is sensitive and selective for the target protein. PMID:23362224

He, Yue; Xing, Xiaojing; Tang, Hongwu; Pang, Daiwen

2013-06-24

332

Polymerase synthesis of DNA labelled with benzylidene cyanoacetamide-based fluorescent molecular rotors: fluorescent light-up probes for DNA-binding proteins.  

PubMed

Viscosity-sensitive fluorophores, fluorescent molecular rotors based on aminobenzylidene-cyanoacetamide moiety, were tethered to 2'-deoxycytidine triphosphate via a propargylamine linker and incorporated into DNA by polymerases in primer extension, nicking enzyme amplification or PCR. DNA probes incorporating modified nucleosides show a light-up response upon binding to a protein. PMID:25704490

Dziuba, Dmytro; Pohl, Radek; Hocek, Michal

2015-03-01

333

Locked-flavylium fluorescent dyes with tunable emission wavelengths based on intramolecular charge transfer for multi-color ratiometric fluorescence imaging.  

PubMed

A new class of locked-flavylium fluorophores with tunable emission wavelengths based on intramolecular charge transfer were designed, synthesized, and evaluated. The optical studies indicate that sensor LF3 can display an intriguing character, fluorescence ratiometric response in three channels by tuning the ICT efficiencies. PMID:25797486

Chen, Hua; Lin, Weiying; Jiang, Wenqing; Dong, Baoli; Cui, Haijun; Tang, Yonghe

2015-04-25

334

Label-free nucleic acids detection based on DNA templated silver nanoclusters fluorescent probe.  

PubMed

Based on DNA templated Ag NCs (DNA/Ag NCs) fluorescent probe, a label-free fluorescent method was developed for the detection of clinical significant DNA fragments from human immunodeficiency virus type 1 (HIV-1) DNA. Firstly, a hairpin probe, containing target DNA recognition sequence and guanine-rich sequence, was designed to hybridize with the target DNA and form a blunt 3'-terminus DNA duplex. Then, exonuclease III (Exo III) was employed to stepwise hydrolyze the mononucleotides from formed blunt 3'-terminus DNA duplex, releasing the target DNA and guanine-rich sequence. Finally, DNA/Ag NCs fluorescent probe was introduced to hybridize with the guanine-rich sequence, leading to an enhanced fluorescence signal for detection. The proposed method could detect as low as 2.9×10(-10)molL(-1) HIV-1 DNA and exhibited excellent selectivity against mismatched target DNA. Furthermore, the method possessed perfect recoveries in cells lysate and human serum, showing potential to be used in biological samples. PMID:25863386

Zhao, Haiyan; Wang, Lei; Zhu, Jing; Wei, Haiping; Jiang, Wei

2015-06-01

335

Engineering and Characterization of New LOV-Based Fluorescent Proteins from Chlamydomonas reinhardtii and Vaucheria frigida.  

PubMed

Flavin-based fluorescent proteins (FbFPs) are a new class of fluorescent reporters that exhibit oxygen-independent fluorescence, which is a key advantage over the green fluorescent protein. Broad application of FbFPs, however, has been generally hindered by low brightness. To maximize the utility of FbFPs, there is a pressing need to expand and diversify the limited FbFP library through the inclusion of bright and robust variants. In this work, we use genome mining to identify and engineer two new FbFPs (CreiLOV and VafLOV) from Chlamydomonas reinhardtii and Vaucheria frigida. We show that CreiLOV is a thermostable, photostable, and fast-maturing monomeric reporter that outperforms existing FbFPs in brightness and operational pH range. Furthermore, we show that CreiLOV can be used to monitor dynamic gene expression in Escherichia coli. Overall, our work introduces CreiLOV as a robust addition to the FbFP repertoire and highlights genome mining as a powerful approach to engineer improved FbFPs. PMID:25881501

Mukherjee, Arnab; Weyant, Kevin B; Agrawal, Utsav; Walker, Joshua; Cann, Isaac K O; Schroeder, Charles M

2015-04-17

336

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

337

Quantification of nanoparticle endocytosis based on double fluorescent pH-sensitive nanoparticles.  

PubMed

Amorphous silica is a particularly interesting material because of its inertness and chemical stability. Silica nanoparticles have been recently developed for biomedical purposes but their innocuousness must be carefully investigated before clinical use. The relationship between nanoparticles physicochemical features, their uptake by cells and their biological activity represents a crucial issue, especially for the development of nanomedicine. This work aimed at adapting a method for the quantification of nanoparticle endocytosis based on pH-sensitive and double fluorescent particles. For that purpose, silica nanoparticles containing two fluorophores: FITC and pHrodo(TM) were developed, their respective fluorescence emission depends on the external pH. Indeed, FITC emits a green fluorescence at physiological pH and pHrodo(TM) emits a red fluorescence which intensity increased with acidification. Therefore, nanoparticles remained outside the cells could be clearly distinguished from nanoparticles uptaken by cells as these latter could be spotted inside cellular acidic compartments (such as phagolysosomes, micropinosomes…). Using this model, the endocytosis of 60 nm nanoparticles incubated with the RAW 264.7 macrophages was quantified using time-lapse microscopy and compared to that of 130 nm submicronic particles. The amount of internalized particles was also evaluated by fluorimetry. The biological impact of the particles was also investigated in terms of cytotoxicity, pro-inflammatory response and oxidative stress. Results clearly demonstrated that nanoparticles were more uptaken and more reactive than submicronic particles. Moreover, we validated a method of endocytosis quantification. PMID:25764066

Kurtz-Chalot, Andréa; Klein, Jean-Philippe; Pourchez, Jérémie; Boudard, Delphine; Bin, Valérie; Sabido, Odile; Marmuse, Laurence; Cottier, Michèle; Forest, Valérie

2015-04-01

338

Blue Fluorescent Dye-Protein Complexes Based on Fluorogenic Cyanine Dyes and Single Chain Antibody Fragments  

PubMed Central

Fluoromodules are complexes formed upon the noncovalent binding of a fluorogenic dye to its cognate biomolecular partner, which significantly enhances the fluorescence quantum yield of the dye. Previously, several single-chain, variable fragment (scFv) antibodies were selected from a yeast cell surface-displayed library that activated fluorescence from a family of unsymmetrical cyanine dyes covering much of the visible and near-IR spectrum. The current work expands our repertoire of genetically encodable scFv-dye pairs by selecting and characterizing a group of scFvs that activate fluorogenic blue-absorbing, blue-fluorescing cyanine dyes, based on oxazole and thiazole heterocycles. The dye binds to both yeast cell surface-displayed and soluble scFvs with low nanomolar Kd values. These dye-protein fluoromodules exhibit high quantum yields, approaching unity for the brightest system. The promiscuity of these scFvs with other fluorogenic cyanine dyes was also examined. Fluorescence microscopy demonstrates that the yeast cell surface-displayed scFvs can be used for multicolor imaging. The prevalence of 405 nm lasers on confocal imaging and flow cytometry systems make these new reagents potentially valuable for cell biological studies. PMID:21180706

Zanotti, Kimberly J.; Silva, Gloria L.; Creeger, Yehuda; Robertson, Kelly L.; Waggoner, Alan S.; Berget, Peter B.; Armitage, Bruce A.

2011-01-01

339

A turn-on coordination nanoparticle-based fluorescent probe for phosphate in human serum.  

PubMed

Coordination nanoparticles (CNPs) are becoming attractive platforms for chemical sensing applications because their unique adjustable properties offer the opportunity to design various luminescent nanoprobes. Here, we present a CNP-based fluorescent nanoprobe, in which fluorophores (rhodamine B, RB) and quenchers (methylene blue, MB) were spontaneously enfolded by coordination networks self-assembled of adenine, biphenyl-4,4'-dicarboxylic acid (BDA) and zinc ions. The aggregation of fluorophores and quenchers in CNPs resulted in a quenched state fluorescence of RB. RB and MB could be released from CNPs in the presence of phosphate, which triggered the fluorescence of RB. On the basis of recognition-driven disassembly principle, a novel turn-on fluorescent probe for the determination of PO4(3-) with a wide response range (0.5-50 ?M) has been successfully applied in the detection of phosphate in human serum samples. This work not only develops a probe for phosphate but also provides a general strategy for designing nanoprobes or nanocarriers towards various targets by altering organic linkers or metal ions. PMID:25690475

Lin, Na; Li, Jian; Lu, Zhixiang; Bian, Longchun; Zheng, Liyan; Cao, Qiue; Ding, Zhongtao

2015-03-01

340

Self-quenching DNA probes based on aggregation of fluorescent dyes  

NASA Astrophysics Data System (ADS)

Here we present a novel class of self-quenching, double-labeled DNA probes based on the formation of non fluorescent H-type dye dimers. We therefore investigated the aggregation behavior of the red-absorbing oxazine derivative MR121 and found a dimerization constant of about 3000 M-1. This dye was successfully used to develop hairpin-structured as well as linear self-quenching DNA probes that report the presence of the target DNA by an increase of the fluorescence intensity by a factor of 3 to 12. Generally fluorescence quenching of the hairpin-structure probes is more efficient compared to the linear probes, whereas the kinetic of the fluorescence increase is significantly slower. The new probes were used for the identification of different mycobacteria and their antibiotic resistant species. As a test system a probe for the identification of a DNA sequence specific for the Mycobacterium xenopi was synthesized differing from the sequence of the Mycobacterium fortuitum by 6 nucleotides. Furthermore we developed a method for the discrimination between the sequences of the wild type and an antibiotic resistant species of Mycobacterium tuberculosis. Both sequences differ by just 2 nucleotides and were detected specifically by the use of competing olignonucleotides.

Schafer, Gabriela; Muller, Matthias; Hafner, Bernhard; Habl, Gregor; Nolte, Oliver; Marme, Nicole; Knemeyer, Jens-Peter

2005-04-01

341

Multicolor Whole-Cell Bacterial Sensing Using a Synchronous Fluorescence Spectroscopy-Based Approach  

PubMed Central

The wide collection of currently available fluorescent proteins (FPs) offers new possibilities for multicolor reporter gene-based studies of bacterial functions. However, the simultaneous use of multiple FPs is often limited by the bleed-through of their emission spectra. Here we introduce an original approach for detection and separation of multiple overlapping fluorescent signals from mixtures of bioreporters strains. The proposed method relies on the coupling of synchronous fluorescent spectroscopy (SFS) with blind spectral decomposition achieved by the Canonical Polyadic (CP) decomposition (also known as Candecomp/Parafac) of three-dimensional data arrays. Due to the substantial narrowing of FP emission spectra and sensitive detection of multiple FPs in a one-step scan, SFS reduced spectral overlap and improved the selectivity of the CP unmixing procedure. When tested on mixtures of labeled E. coli strains, the SFS/CP approach could easily extract the contribution of at least four overlapping FPs. Furthermore, it allowed to simultaneously monitor the expression of three iron responsive genes and pyoverdine production in P. aeruginosa. Implemented in a convenient microplate format, this multiplex fluorescent reporter method provides a useful tool to study complex processes with different variables in bacterial systems. PMID:25822488

Parrello, Damien; Mustin, Christian; Brie, David; Miron, Sebastian; Billard, Patrick

2015-01-01

342

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

343

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

344

Highly sensitive and selective fluorescence detection of copper (II) ion based on multi-ligand metal chelation.  

PubMed

A fluorescent probe was synthesized and demonstrated to be highly selective and sensitive in the reaction with copper (II) ion, generating a large variation of the fluorescence intensity in a dose-response manner. The probe contains a dansyl moiety as fluorophore and a multidentate ligand for copper (II) ion recognition. The reaction of the molecular probe with copper (II) ion proceeds rapidly and irreversibly in a 1 to 1 stoichiometric way, leading to the production of stable copper (II) complex, which subsequently results in the quenching of fluorescence. The detection limit for copper (II) ion was measured to be about 2ppb. It was also shown that the probe has high selectivity for copper (II) ion and good anti-interference ability against other transition metal ions. The herein reported very simple and reliable fluorescence probe could be employed for copper (II) ion detection in many aspects. PMID:24881551

Zhang, Shan; Yu, Tao; Sun, Mingtai; Yu, Huan; Zhang, Zhongping; Wang, Suhua; Jiang, Hui

2014-08-01

345

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

346

Upconversion nanoparticle-based fluorescence resonance energy transfer assay for organophosphorus pesticides.  

PubMed

This paper reports a novel nanosensor for organophosphorus pesticides based on the fluorescence resonance energy transfer (FRET) between NaYF4:Yb,Er upconversion nanoparticles (UCNPs) and gold nanoparticles (AuNPs). The detection mechanism is based on the facts that AuNPs quench the fluorescence of UCNPs and organophosphorus pesticides (OPs) inhibit the activity of acetylcholinesterase (AChE) which catalyzes the hydrolysis of acetylthiocholine (ATC) into thiocholine. Under the optimized conditions, the logarithm of the pesticides concentration was proportional to the inhibition efficiency. The detection limits of parathion-methyl, monocrotophos and dimethoate reached 0.67, 23, and 67ng/L, respectively. Meanwhile, the biosensor shows good sensitivity, stability, and could be successfully applied to detection of OPs in real food samples, suggesting the biosensor has potentially extensive application clinic diagnoses assays. PMID:25569873

Long, Qian; Li, Haitao; Zhang, Youyu; Yao, Shouzhuo

2015-06-15

347

Intracellular fluorescent temperature probe based on triarylboron substituted poly N-isopropylacrylamide and energy transfer.  

PubMed

A novel hydrophilic fluorescence temperature probe (PNDP) based on polarity-sensitive triarylboron compound (DPTB) and PNIPAM is designed and synthesized. In order to overcome the shortcomings of the single-intensity-based sensing mechanism and obtain more robust signals, ratiometric readout is achieved by designing an efficient FRET system (PNDP-NR) between DPTB and Nile Red (NR). PNDP-NR possesses some excellent features, including wide temperature range, good linear relationship, high temperature resolution, excellent reversibility, and stability. Within a sensing temperature range of 30-55 °C, the fluorescence color of PNDP-NR experiences significant change from red to green-blue. PNDP-NR is also introduced into NIH/3T3 cells to sense the temperature at the single-cell level. It gave excellent photostability and low cytotoxicity in vivo. PMID:25753485

Liu, Jun; Guo, Xudong; Hu, Rui; Xu, Jian; Wang, Shuangqing; Li, Shayu; Li, Yi; Yang, Guoqiang

2015-04-01

348

Fluorescent quenching-based quantitative detection of specific DNA/RNA using a BODIPY((R)) FL-labeled probe or primer.  

PubMed

We have developed a simple method for the quantitative detection of specific DNA or RNA molecules based on the finding that BODIPY((R)) FL fluorescence was quenched by its interaction with a uniquely positioned guanine. This approach makes use of an oligonucleotide probe or primer containing a BODIPY((R)) FL-modified cytosine at its 5'-end. When such a probe was hybridized with a target DNA, its fluorescence was quenched by the guanine in the target, complementary to the modified cytosine, and the quench rate was proportional to the amount of target DNA. This widely applicable technique will be used directly with larger samples or in conjunction with the polymerase chain reaction to quantify small DNA samples. PMID:11239011

Kurata, S; Kanagawa, T; Yamada, K; Torimura, M; Yokomaku, T; Kamagata, Y; Kurane, R

2001-03-15

349

Real-time fluorescence assays of alkaline phosphatase and ATP sulfurylase activities based on a novel PPi fluorescent probe.  

PubMed

An anthracene-armed tetraaza macrocyclic fluorescent probe 3-(9-anthrylmethyl)-3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene(l) for detecting Zn(2+) in aqueous medium was synthesized. L-Zn(2+) complex, showed selectivity toward pyrophosphate ion (PPi) by quenching the fluorescence in aqueous HEPES buffer (pH 7.4). Furthermore, L-Zn(2+) was also used to set up a real-time fluorescence assay for monitoring enzyme activities of alkaline phosphatase (ALP) and adenosine triphosphate sulfurylase (ATPS). In the presence of ALP inhibitor Na3VO4 and ATPS inhibitor chlorate, two enzymes activities decreased obviously, respectively. PMID:25770619

Wang, Xiaobo; Zhang, Zhiyang; Ma, Xiaoyan; Wen, Jinghan; Geng, Zhirong; Wang, Zhilin

2015-05-01

350

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

PubMed

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

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

2014-11-21

351

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

Microsoft Academic Search

This article presents the first evidence that the DNA base analogue 1,3-diaza-2-oxophenoxazine, tCO, is highly fluorescent, both as free nucleoside and incorporated in an arbitrary DNA structure. tCO is thoroughly characterized with respect to its photo- physical properties and structural performance in single- and double-stranded oligonucleotides. The lowest energy absorption band at 360 nm (e ¼ 9000 M21 cm21) is

Peter Sandin; Karl Borjesson; Hong Li; Jerker Ma; Tom Brown; L. Marcus Wilhelmsson; Bo Albinsson

2008-01-01

352

A fluorescence-based microbial sensor for the selective detection of gold.  

PubMed

This study presents a fluorescence-based microbial sensor for the detection of metal ions as a novel analytical tool for environmental applications. Our results demonstrate the effectiveness of whole-cell sensors in the selective detection of gold ions. Two heavy-metal-tolerant proteobacteria, Cupriavidus metallidurans and Ralstonia eutropha, were examined and showed great specificity. This work highlights the potential of employing engineered microbial strains as robust analytical tools. PMID:24394407

Tseng, Hsueh-Wei; Tsai, Yi-Jung; Yen, Jia-Ho; Chen, Pei-Hsuan; Yeh, Yi-Chun

2014-02-18

353

Mesh-based Monte Carlo code for fluorescence modeling in complex tissues with irregular boundaries  

Microsoft Academic Search

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

Robert H. Wilson; Leng-Chun Chen; William Lloyd; Shiuhyang Kuo; Cynthia Marcelo; Stephen E. Feinberg; Mary-Ann Mycek

2011-01-01

354

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

Microsoft Academic Search

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

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

2010-01-01

355

New Emergent Nanotechnologies in Medical and Biochemical Applica- tions: Advanced Fluorescence Protein-Based Nanosensors  

Microsoft Academic Search

In this review we explore the advantages deriving from the use of either enzymes or binding proteins to de- velop non-consuming substrate fluorescence biosensors. We report on a novel approach to address the consumption of substrate by enzyme-based biosensors, namely the utilization of apo-enzymes as non-active forms of proteins, which through still able to bind the ligand yet cannot transform

Maria Staiano; Marcella de Champdoré; Stefano Borini; Andrea M. Rossi; Mosè Rossi; Sabato D'Auria

2007-01-01

356

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

PubMed

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

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

2015-04-01

357

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

358

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

PubMed Central

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

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

2014-01-01

359

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

PubMed

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

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

2013-11-01

360

Analysis of lignans from Phyllanthus niruri L. in plasma using a simple HPLC method with fluorescence detection and its application in a pharmacokinetic study.  

PubMed

A simple analytical method using HPLC with fluorescence detection was developed for the simultaneous determination of four lignans, phyllanthin (1), hypophyllanthin (2), phyltetralin (3) and niranthin (4) from Phyllanthus niruri L. in plasma. The method recorded limits of detection for 1, 2, 3 and 4 as 1.22, 6.02, 0.61 and 1.22 ng/ml, respectively, at a signal-to-noise ratio of 5:1 whereas their limits of quantification were 4.88, 24.41, 4.88 and 9.76 ng/ml, respectively, at a signal-to-noise ratio of 12:1. These values were comparable to those of other sensitive methods such as gas chromatography-mass spectrometry (GC-MS), high-performance liquid chromatography-MS (HPLC-MS) and HPLC-electrochemical detection (HPLC-ECD) for the analysis of plasma lignans. A further advantage over known methods was its simple protocol for sample preparation. The within-day and between-day accuracies for the analysis of the four lignans were between 87.69 and 110.07% with precision values below 10.51%. Their mean recoveries from extraction were between 91.39 and 114.67%. The method was successfully applied in the pharmacokinetic study of lignans in rats. Following intravenous administration, the lignans were eliminated slowly from the body with a mean clearance of 0.04, 0.01, 0.03 and 0.02 l/kg h and a mean half-life of 3.56, 3.87, 3.35 and 4.40 h for 1, 2, 3 and 4, respectively. Their peak plasma concentration upon oral administration was 0.18, 0.56, 0.12 and 0.62 microg/ml, respectively, after 1h. However, their absorption was incomplete with a calculated absolute oral bioavailability of 0.62, 1.52, 4.01 and 2.66% for 1, 2, 3 and 4, respectively. PMID:17261384

Murugaiyah, Vikneswaran; Chan, Kit Lam

2007-06-01

361

Quantitative Imaging of Glutathione in Live Cells Using a Reversible Reaction-Based Ratiometric Fluorescent Probe  

PubMed Central

Glutathione (GSH) plays an important role in maintaining redox homeostasis inside cells. Currently, there are no methods available to quantitatively assess the GSH concentration in live cells. Live cell fluorescence imaging revolutionized the field of cell biology and has become an indispensable tool in current biological studies. In order to minimize the disturbance to the biological system in live cell imaging, the probe concentration needs to be significantly lower than the analyte concentration. Because of this, any irreversible reaction-based GSH probe can only provide qualitative results within a short reaction time and will exhibit maximum response regardless of the GSH concentration if the reaction is completed. A reversible reaction-based probe with an appropriate equilibrium constant allows measurement of an analyte at much higher concentrations and, thus, is a prerequisite for GSH quantification inside cells. In this contribution, we report the first fluorescent probe—ThiolQuant Green (TQ Green)—for quantitative imaging of GSH in live cells. Due to the reversible nature of the reaction between the probe and GSH, we are able to quantify mM concentrations of GSH with TQ Green concentrations as low as 20 nM. Furthermore, the GSH concentrations measured using TQ Green in 3T3-L1, HeLa, HepG2, PANC-1, and PANC-28 cells are reproducible and well correlated with the values obtained from cell lysates. TQ Green imaging can also resolve the changes in GSH concentration in PANC-1 cells upon diethylmaleate (DEM) treatment. In addition, TQ Green can be conveniently applied in fluorescence activated cell sorting (FACS) to measure GSH level changes. Through this study, we not only demonstrate the importance of reaction reversibility in designing quantitative reaction-based fluorescent probes but also provide a practical tool to facilitate redox biology studies. PMID:25531746

2014-01-01

362

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

E-print Network

A simple birth-death-migration individual-based model for biofilm development Nabil Mabrouk only three main processes: birth (binary fission), death (or detachment) and surface migration (death) of a bacterium · migration of a bacterium to a new location Birth is a process by which a parent

Paris-Sud XI, Université de

363

METHODOLOGY Open Access Protocol: A simple phenol-based method for 96-well  

E-print Network

METHODOLOGY Open Access Protocol: A simple phenol-based method for 96-well extraction of high-throughput RNA extraction in 96-well format, only one non- kit method has been described in the literature using ability to simultaneously extract both DNA and RNA in a small number of steps [2]. However, some concerns

Howard, Martin

364

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

E-print Network

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

Girod, Bernd

365

The subject is based upon the simple principles of electronics, but takes it to more exciting  

E-print Network

The subject is based upon the simple principles of electronics, but takes it to more exciting renewable generation to converting supplies for use in consumer electronics. This is by no means an exhaustive list of the coverage of electronics and electrical engineering, and in today's world it is hard

Schnaufer, Achim

366

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

367

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

368

A simple scheme to make passwords based on one-way functions much harder to crack  

Microsoft Academic Search

We present a simple scheme that makes guessing passwords based on one-way functions 100 to 1000 times harder. The scheme is easy to program and easy to incrementally add to existing schemes. In particular, there is no need to switch to it all at the same time. Old passwords will still work and have the same security as before (one

Udi Manber

1996-01-01

369

Research article Simple rules based on pile slope are used in the self organization  

E-print Network

Research article Simple rules based on pile slope are used in the self organization of sand pile the hypothesis that slope influences where worker ants deposit excavated soil on piles near the nest entrance. We predicted that ants will deposit their load near the top of a pile where the slope changes from upward

Tofilski , Adam

370

Simple method for the synthesis of bicyclic pyridine bases from 1-ethynylcycloalkanols and carboxylic acid chlorides  

Microsoft Academic Search

A new, simple and effective method was developed for the synthesis of difficultly obtainable bicyclic pyridine bases by the condensation of cyclic ethynylcarbinols with carboxylic acid anhydrides in the presence of an equimolar ZnCl2-POCl3 mixture followed by treatment with ammonium hydroxide.

F. A. Selimov; O. G. Rutman; U. M. Dzhemilev

1988-01-01

371

A SIMPLE CORRELATION-BASED MODEL OF INTELLIGIBILITY FOR NONLINEAR SPEECH ENHANCEMENT AND SEPARATION  

E-print Network

A SIMPLE CORRELATION-BASED MODEL OF INTELLIGIBILITY FOR NONLINEAR SPEECH ENHANCEMENT AND SEPARATION of highly nonlinear speech enhancement techniques, we contend that SNR is not useful; instead we propose of such systems. 1. INTRODUCTION Speech enhancement concerns taking a target speech signal that has been corrupted

Ellis, Dan

372

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

ERIC Educational Resources Information Center

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

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

2011-01-01

373

Design and implementation of a simple data query system based on PHP + TXT database  

Microsoft Academic Search

Starting from practical application,this paper designs a simple data query system, which uses PHP + TXT database technology under Web server environment based on Unix system. The system can be applied to various types of data in WEB real-time online inquiry, and it has extensive application value.

Jia Gui-jun; Dong Yu-min; Cai Wen-yi

2010-01-01

374

Sprite: A Simple, Cheat-Proof, Credit-Based System for Mobile Ad-Hoc Networks  

Microsoft Academic Search

Mobile ad hoc networking has been an active research area for several years. How to stimulate cooperation among selfish mobile nodes, however, is not well addressed yet. In this paper, we propose Sprite, a simple, cheat-proof, credit- based system for stimulating cooperation among selfish nodes in mobile ad hoc networks. Our system provides incentive for mobile nodes to cooperate and

Sheng Zhong; Jiang Chen; Yang Richard Yang

2002-01-01

375

Sprite: A Simple, Cheat-Proof, Credit-Based System for Mobile Ad-Hoc Networks  

Microsoft Academic Search

Abstract— Mobile ad hoc networking has been an active research area for several years. How to stimulate cooperation among selfish mobile nodes, however, is not well addressed yet. In this paper, we propose Sprite, a simple, cheat-proof, credit- based system for stimulating cooperation among selfish nodes in mobile ad hoc networks. Our system provides incentive for mobile nodes to cooperate

Sheng Zhong; Jiang Chen; Yang Richard Yang

2003-01-01

376

A Simple Performance Analysis of Multiple Access RFID Networks Based on the Binary Tree Protocol  

Microsoft Academic Search

In this paper, we propose a simple performance analysis of radio frequency identification (RFID) networks , based on the binary tree medium access control (MAC) pro- tocol. We evaluate various network performance metrics, such as throughput, delay and average number of packets needed to take a census of the RFID tags. In order to validate our analytical results, we develop

F. Cappelletti; G. Ferrari; R. Raheli

2006-01-01

377

Anion recognition by simple chromogenic and chromo-fluorogenic salicylidene Schiff base or reduced-Schiff base receptors  

NASA Astrophysics Data System (ADS)

This review contains extensive application of anion sensing ability of salicylidene type Schiff bases and their reduced forms having various substituents with respect to phenolic sbnd OH group. Some of these molecular systems behave as receptor for recognition or sensing of various anions in organic or aqueous-organic binary solvent mixture as well as in the solid supported test kits. Development of Schiff base or reduced Schiff base receptors for anion recognition event is commonly based on the theory of hydrogen bonding interaction or deprotonation of phenolic -OH group. The process of charge transfer (CT) or inhibition of excited proton transfer (ESIPT) or followed by photo-induced electron transfer (PET) lead to naked-eye color change, UV-vis spectral change, chemical shift in the NMR spectra and fluorescence spectral modifications. In this review we have tried to discuss about the anion sensing properties of Schiff base or reduced Schiff base receptors.

Dalapati, Sasanka; Jana, Sankar; Guchhait, Nikhil

2014-08-01

378

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

PubMed

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

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

2014-12-18

379

High-Performance Fluorescence Molecular Tomography through Shape-Based Reconstruction Using Spherical Harmonics Parameterization  

PubMed Central

Fluorescence molecular tomography in the near-infrared region is becoming a powerful modality for mapping the three-dimensional quantitative distributions of fluorochromes in live small animals. However, wider application of fluorescence molecular tomography still requires more accurate and stable reconstruction tools. We propose a shape-based reconstruction method that uses spherical harmonics parameterization, where fluorophores are assumed to be distributed as piecewise constants inside disjointed subdomains and the remaining background. The inverse problem is then formulated as a constrained nonlinear least-squares problem with respect to shape parameters, which decreases ill-posedness because of the significantly reduced number of unknowns. Since different shape parameters contribute differently to the boundary measurements, a two-step and modified block coordinate descent optimization algorithm is introduced to stabilize the reconstruction. We first evaluated our method using numerical simulations under various conditions for the noise level and fluorescent background; it showed significant superiority over conventional voxel-based methods in terms of the spatial resolution, reconstruction accuracy with regard to the morphology and intensity, and robustness against the initial estimated distribution. In our phantom experiment, our method again showed better spatial resolution and more accurate intensity reconstruction. Finally, the results of an in vivo experiment demonstrated its applicability to the imaging of mice. PMID:24732826

Wang, Daifa; He, Jin; Qiao, Huiting; Song, Xiaolei; Fan, Yubo; Li, Deyu

2014-01-01

380

A fluorescent aptasensor based on DNA-scaffolded silver-nanocluster for ochratoxin A detection.  

PubMed

The selective detection of ultratrace amounts of ochratoxin A (OTA) is extremely important for food safety since it is one of the most toxic and widespread mycotoxin. Here we develop a signal-on fluorescent biosensor for detection of OTA based on fluorescent DNA-scaffolded silver-nanocluster (AgNCs), structure-switching of anti-OTA aptamer (Ap) and magnetic beads (MBs), and demonstrate its feasibility in the application of detecting OTA in real samples of wheat. The method exhibits superior sensitivity with a detection limit as low as 2 pg/mL OTA with high specificity. To the best of our knowledge, this is the first attempt to detect OTA based on DNA-scaffolded AgNCs, which possesses relatively high fluorescence quantum yield and photostability with regard to traditional organic dyes and quantum dots. Moreover, combined with the merits of MBs and aptamer, the proposed sensor has many advantages such as fabrication easiness, operation convenience, low cost, and being fast and portable, which may represent a promising path toward routine OTA control. PMID:24590125

Chen, Jinghua; Zhang, Xi; Cai, Shuxian; Wu, Dongzhi; Chen, Mei; Wang, Shihua; Zhang, Jing

2014-07-15

381

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

382

A Cu(2+)-selective fluorescent chemosensor based on BODIPY with two pyridine ligands and logic gate.  

PubMed

A novel near-infrared fluorescent chemosensor based on BODIPY (Py-1) has been synthesized and characterized. Py-1 displays high selectivity and sensitivity for sensing Cu(2+) over other metal ions in acetonitrile. Upon addition of Cu(2+) ions, the maximum absorption band of Py-1 in CH3CN displays a red shift from 603 to 608nm, which results in a visual color change from pink to blue. When Py-1 is excited at 600nm in the presence of Cu(2+), the fluorescent emission intensity of Py-1 at 617nm is quenched over 86%. Notably, the complex of Py-1-Cu(2+) can be restored with the introduction of EDTA or S(2-). Consequently, an IMPLICATION logic gate at molecular level operating in fluorescence mode with Cu(2+) and S(2-) as chemical inputs can be constructed. Finally, based on the reversible and reproducible system, a nanoscale sequential memory unit displaying "Writing-Reading-Erasing-Reading" functions can be integrated. PMID:25766475

Huang, Liuqian; Zhang, Jing; Yu, Xiaoxiu; Ma, Yifan; Huang, Tianjiao; Shen, Xi; Qiu, Huayu; He, Xingxing; Yin, Shouchun

2015-06-15

383

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

384

Biosensor platform based on surface plasmon-enhanced fluorescence spectroscopy and responsive hydrogel binding matrix  

NASA Astrophysics Data System (ADS)

We report a novel biosensor platform based on surface plasmon-enhanced fluorescence spectroscopy (SPFS) and a responsive N-isopropylacrylamide (NIPAAm) hydrogel binding matrix. This binding matrix highly swells in aqueous environment and it can be modified with receptor biomolecules by using active ester coupling chemistry. After the binding of target analyte molecules contained in a sample by receptor biomolecules immobilized in the hydrogel matrix, the captured analyte molecules can be compacted on the surface through the collapse of the gel triggered by an external stimulus. A thin hydrogel NIPAAm-based film was attached to a gold sensor surface and modified with mouse IgG receptor molecules. The affinity binding of antibodies against mouse IgG that were labeled with Alexa Fluor chromophores was observed by surface plasmon-enhanced fluorescence spectroscopy. We demonstrate that the collapse of the hydrogel matrix results in the enhancement of measured fluorescence intensity owing to the increase in the concentration of captured molecules within the evanescent field of surface plasmons.

Huang, Chun-Jen; Jonas, Ulrich; Dostálek, Jakub; Knoll, Wolfgang

2009-05-01

385

High-performance fluorescence molecular tomography through shape-based reconstruction using spherical harmonics parameterization.  

PubMed

Fluorescence molecular tomography in the near-infrared region is becoming a powerful modality for mapping the three-dimensional quantitative distributions of fluorochromes in live small animals. However, wider application of fluorescence molecular tomography still requires more accurate and stable reconstruction tools. We propose a shape-based reconstruction method that uses spherical harmonics parameterization, where fluorophores are assumed to be distributed as piecewise constants inside disjointed subdomains and the remaining background. The inverse problem is then formulated as a constrained nonlinear least-squares problem with respect to shape parameters, which decreases ill-posedness because of the significantly reduced number of unknowns. Since different shape parameters contribute differently to the boundary measurements, a two-step and modified block coordinate descent optimization algorithm is introduced to stabilize the reconstruction. We first evaluated our method using numerical simulations under various conditions for the noise level and fluorescent background; it showed significant superiority over conventional voxel-based methods in terms of the spatial resolution, reconstruction accuracy with regard to the morphology and intensity, and robustness against the initial estimated distribution. In our phantom experiment, our method again showed better spatial resolution and more accurate intensity reconstruction. Finally, the results of an in vivo experiment demonstrated its applicability to the imaging of mice. PMID:24732826

Wang, Daifa; He, Jin; Qiao, Huiting; Song, Xiaolei; Fan, Yubo; Li, Deyu

2014-01-01

386

Simple Computer Vision System for Chess Playing Robot Manipulator as a Project-based Learning Example  

Microsoft Academic Search

This paper presents an example of project-based learning (PBL) in an undergraduate course on Image processing. The design of a simple, low-cost computer vision system for implementation on a chess-playing capable robot is discussed. The system is based on a standard CCD camera and a personal computer. This project is a good tool for learning most of the course material

E. Sokic; M. Ahic-Djokic

2008-01-01

387

Aptamer-based detection of epithelial tumor marker mucin 1 with quantum dot-based fluorescence readout.  

PubMed

Mucin 1 (MUC1) is a glycoprotein expressed on most epithelial cell surfaces, which has been confirmed as a useful biomarker for the diagnosis of early cancers. In this paper, we report an aptamer-based, quantitative detection protocol for MUC1 using a 3-component DNA hybridization system with quantum dot (QD)-labeling: in the absence of MUC1 peptides, strong fluorescence is observed upon mixing the three specially designed DNA strands (quencher, QD-labeled reporter, and the MUC1 aptamer stem); in the presence of MUC1 peptides, a successive decrease in fluorescence intensity is detected since the MUC1 peptide binds to the aptamer strand in such a way to allow the quencher and fluorescence reporter to be brought into close proximity (which leads to the occurrence of fluorescence resonance energy transfer, FRET, between the quencher and QD). The detection limit for MUC1 with this novel approach is in the nanomolar (nM) level, and a linear response can be established for the approximate range found in blood serum. This study also provided further insight into the aptamer/analyte binding site/mode for MUC1, which augments the possibility of improving this detection methodology for the early diagnosis of different types of epithelial cancers of large populations. PMID:19572710

Cheng, Alan K H; Su, Huaipeng; Wang, Y Andrew; Yu, Hua-Zhong

2009-08-01

388

NO2-based laser-induced fluorescence (LIF) technique to measure cold-flow mixing  

NASA Astrophysics Data System (ADS)

The paper examines the sensitivity and resolution capabilities of NO2-based laser-induced fluorescence (LIF) for studying cold-flow mixing in high-pressure applications. Calibrated fuel-air mixtures with known NO2 concentrations are investigated with LIF in cases of high pressures of up to 200 psig. The redshifted fluorescence is monitored during excitation by a CW argon-ion laser, and attention is given to the effects of pressure and mixture composition on signal quenching. Calibration is used to account for the quenching effects, and a resolution of 0.2 percent of the fuel stream is demonstrated at atmospheric pressures. At very high pressures the dynamic range is reduced, and some practical considerations are discussed regarding the practical application of the technique. The technique is shown to resolve small fuel-air eddies with good spatial and temporal resolution when applied to the study of a turbulent jet in coflowing air.

Gulati, A.; Warren, R. E., Jr.

1992-01-01

389

NO2-based laser-induced fluorescence (LIF) technique to measure cold-flow mixing  

SciTech Connect

The paper examines the sensitivity and resolution capabilities of NO2-based laser-induced fluorescence (LIF) for studying cold-flow mixing in high-pressure applications. Calibrated fuel-air mixtures with known NO2 concentrations are investigated with LIF in cases of high pressures of up to 200 psig. The redshifted fluorescence is monitored during excitation by a CW argon-ion laser, and attention is given to the effects of pressure and mixture composition on signal quenching. Calibration is used to account for the quenching effects, and a resolution of 0.2 percent of the fuel stream is demonstrated at atmospheric pressures. At very high pressures the dynamic range is reduced, and some practical considerations are discussed regarding the practical application of the technique. The technique is shown to resolve small fuel-air eddies with good spatial and temporal resolution when applied to the study of a turbulent jet in coflowing air. 9 refs.

Gulati, A.; Warren, R.E., JR. (General Electric Co., Schenectady, NY (United States))

1992-01-01

390

DO-sensing based on enhancement of cladding fluorescence in dye-doped plastic fiber  

NASA Astrophysics Data System (ADS)

A new technique for the optical sensing of dissolved oxygen (DO) is proposed here. It is based on the enhancement in fluorescence yield of TPP dye at (lambda) equals 656 nm, when excited by He-Cd blue laser of (lambda) equals 441 nm in the presence of dissolved oxygen. The sensor head was fabricated by cladding the ARTON fiber core with the poly-4-methyl-1- pentene polymer matrix suitably doped with Tetraphenylporphine dye. This sensor head, when placed in a test chamber and end-pumped by He-Cd laser, generates the intense fluorescence at 656 nm. Its intensity was noticed to increase with increasing the amount of DO. A theoretical model of the sensor response was designed and is also discussed.

Vishnoi, Gargi; Morisawa, Masayuki; Muto, Shinzo

1998-09-01

391

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

PubMed Central

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

Wu, Qijun; Wang, Lufei; Zu, Lily

2011-01-01

392

Phosphazene based multicentered naked-eye fluorescent sensor with high selectivity for Fe3+ ions.  

PubMed

A novel on/off fluorescent rhodamine-based hexapodal Fe(3+) probe (L) containing a cyclotriphosphazene core was synthesized by an azide-alkyne "click-reaction". The synthesized compounds (1-5 and L) were characterized by FT-IR; (1)H, (13)C, and (31)P NMR; and MALDI MS spectrometry. The optical sensor features for the Fe(3+) complex of L were investigated by UV-vis and fluorescence spectroscopy. The stoichiometry of L-Fe(3+) complex was found to be 1:3 (ligand/metal ion), and the detection limit of L was determined as 4.8 ?M (0.27 mg L(-1)) for Fe(3+) ions. The reusability of the sensor was tested by the addition of ethylenediamine to L-Fe(3+) complex solutions followed by the addition of Fe(3+) solution. PMID:24498930

Kagit, Reyhan; Yildirim, Mehmet; Ozay, Ozgur; Yesilot, Serkan; Ozay, Hava

2014-02-17

393

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

394

Development of an alcohol optode membrane based on fluorescence enhancement of fluorescein derivatives.  

PubMed

A new type of optode membrane for the determination of alcohols, such as methanol, ethanol, propan-1-ol and propan-2-ol etc, is presented that can be exploited in optical and fibre-optic sensors. It is based on the use of a new lipophilic fluorescent reagent, namely fluorescein octadecyl ester (FODE), which is immobilized in a plasticized PVC membrane. The response mechanism relies on the fact that FODE can reversibly recognize alcohol molecules due to the hydrogen bonding formation between FODE and alcohol molecules. The analytical information in this membrane is the enhancement of the relative fluorescence intensity measured at 527 nm (463 nm, excitation). Under the optimum condition, the membrane has a wide measuring range for alcohol samples. The membrane has been applied to determine the concentration of ethanol in alcoholic drinks with satisfactory results. PMID:18966024

Zeng, H H; Wang, K M; Li, D; Yu, R Q

1994-06-01

395

KF polymerase-based fluorescence aptasensor for the label-free adenosine detection.  

PubMed

We have developed a simple, inexpensive, and label-free method for the selective detection of adenosine. Klenow fragment polymerase (KF polymerase) is a commonly-used 5' to 3' DNA polymerase, it also has 3' to 5' exonuclease activity that can digest single-stranded DNA. An adenosine binding DNA aptamer was employed, the aptamer was split into two pieces of single-stranded DNA (aptamer-A1 + aptamer-A2). Without the addition of adenosine, aptamer-A1 and aptamer-A2 existed as single-stranded DNA which could be efficiently degraded by the exonuclease activity of KF polymerase. Much reduced background fluorescence was obtained when SYBR Green dye was added. However, in the presence of adenosine, aptamer-A1 and aptamer-A2 bound to adenosine, and hybridization of the complementary sequences resulted in the formation of a duplex DNA structure, which could initiate DNA polymerization. The addition of SYBR Green dye resulted in a very high fluorescence enhancement, which could be used for the quantification of adenosine. PMID:22183639

Liao, Dongli; Jiao, Huping; Wang, Bin; Lin, Quan; Yu, Cong

2012-02-21

396

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

PubMed

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

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

2014-04-10

397

A rhodamine/BODIPY-based fluorescent probe for the differential detection of Hg(II) and Au(III).  

PubMed

We described the design and synthesis of a molecular sensor based on a rhodamine/BODIPY platform that displayed differential fluorescence responses towards Hg(2+) and Au(3+) and demonstrated its utility in intracellular ion imaging. PMID:24322884

Karaku?, Erman; Üçüncü, Muhammed; Emrullaho?lu, Mustafa

2014-02-01

398

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

399

Fiber-optic fluorescence sensor for dissolved oxygen detection based on fluorinated xerogel immobilized with ruthenium (II) complex  

Microsoft Academic Search

A fiber-optic sensor based on fluorescence quenching was designed for dissolved oxygen (DO) detection. The fluorinated xerogel-based\\u000a sensing film of the present sensor was prepared from 3, 3, 3-trifluoropropyltrimethoxysilane (TFP–TriMOS). Oxygen-sensitive\\u000a fluorophores of tris (2, 2?- bipyridine) ruthenium (II) (Ru(bpy)32+) were immobilized in the sensing film and the emission fluorescence was quenched by dissolved oxygen. In the sensor fabrication,\\u000a a

Yan XiongJing; Jing Xu; Dao-qian Zhu; Chun-feng Duan; Ya-feng Guan

2010-01-01

400

An ultrasensitive fluorescence assay for protein detection by hybridization chain reaction-based DNA nanotags.  

PubMed

An ultrasensitive fluorescence method for determination of protein is developed based on hybridization chain reaction (HCR). In this assay, the streptavidin-magnetic nanobeads were conjugated to biotinylated initiators and biotinylated anti-IgG. In the presence of human IgG, the magnetic nanobeads were fixed on the substrate and the carried initiators propagated the chain reaction of hybridization to form the nicked polymers. Because the nanobead probe carries with a large number of oligonucleotides per protein binding event, there is obvious amplification in the nicked polymers. Then, numerous SYBR Green I molecules were intercalated into the grooves of the long dsDNA polymers, generating a substantially apparent increase in the corresponding fluorescence intensity. With HCR amplification and magenetic nanobead to preamplify the fluorescence signal and reduce the background signal, the detection limit of this assay was 14 aM. Compared with the reported protein detection methods, our method exhibited ultrahigh sensitivity. In addition, the proposed method possessed excellent selectivity and low matrix effect. What is more, the assay was also studied for clinical application in human serum with a satisfactory and reliable result. PMID:24001583

Dai, Shuang; Xue, Qingwang; Zhu, Jing; Ding, Yongshun; Jiang, Wei; Wang, Lei

2014-01-15

401

Immunoassays based on surface-enhanced fluorescence using gap-plasmon-tunable Ag bilayer nanoparticle films.  

PubMed

A novel gap-plasmon-tunable Ag bilayer nanoparticle film for immunoassays is demonstrated. Different from a traditional Ag monolayer nanoparticle film, a desired number of polyelectrolyte (PEL) layers are deposited on the nanoparticles before the self-assembly of a second Ag nanoparticle layer. Interestingly, by controlling the number of the PEL interlayers, the gap plasmon between the two Ag nanoparticle layers can be tuned across the visible spectral range. The ability of the presented Ag bilayer nanoparticle films in fluorescence enhancement has been examined experimentally. A maximal enhancement of around 15.4 fold was achieved when 7 layers of polyelectrolyte were used. When this optimal Ag bilayer nanoparticle film was applied to fluorescence immunoassay, a performance with approximately 3.3-fold enhancement was obtained compared with that performed on a traditional glass substrate. The experimental results suggest that the presented gap-plasmon tunable Ag bilayer nanoparticle films have great potential in fluorescence-based immunoassays. The method of the bilayer-film construction presented here also provides new insights into the rational design of the plasmonic substrates. PMID:22890683

Zhang, Ruohu; Wang, Zhuyuan; Song, Chunyuan; Yang, Jing; Sadaf, Asma; Cui, Yiping

2013-01-01

402

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

PubMed

The detection of nitroaromatics in aqueous solutions by a novel pyrene-functionalized film has been investigated in the present study. The pyrene moieties were attached on the glass surface via a long flexible spacer based on self-assembled monolayer technique. Steady-state fluorescence measurements revealed that these surface-attached pyrene moieties exhibited both monomer and excimer emission. Nitroaromatics such as 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, and 2,4,6-trinitrophenol (picric acid) were found to efficiently quench the fluorescence emission of this film. The quenching results demonstrated that the excimer emission of these surface-confined pyrene moieties is more sensitive to the presence of nitroaromatics than the monomer emission. The quenching mechanism was examined through fluorescence lifetime measurement and it revealed that the quenching is static in nature and may be caused by electron transfer from the polycyclic aromatics to the nitroaromatics. Furthermore, the response of the film to nitroaromatics is fast and reversible, and the obtained film shows promising potentials in detecting explosives in aqueous environment. PMID:22750335

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

2012-11-01

403

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

PubMed

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

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

2015-04-01

404

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

PubMed

An optical DNA biosensor based on fluorescence resonance energy transfer (FRET) utilizing synthesized quantum dot (QD) has been developed for the detection of specific-sequence of DNA for Ganoderma boninense, an oil palm pathogen. Modified QD that contained carboxylic groups was conjugated with a single-stranded DNA probe (ssDNA) via amide-linkage. Hybridization of the target DNA with conjugated QD-ssDNA and reporter probe labeled with Cy5 allows for the detection of related synthetic DNA sequence of Ganoderma boninense gene based on FRET signals. Detection of FRET emission before and after hybridization was confirmed through the capability of the system to produce FRET at 680 nm for hybridized sandwich with complementary target DNA. No FRET emission was observed for non-complementary system. Hybridization time, temperature and effect of different concentration of target DNA were studied in order to optimize the developed system. The developed biosensor has shown high sensitivity with detection limit of 3.55 × 10(-9) M. TEM results show that the particle size of QD varies in the range between 5 to 8 nm after ligand modification and conjugation with ssDNA. This approach is capable of providing a simple, rapid and sensitive method for detection of related synthetic DNA sequence of Ganoderma boninense. PMID:25587406

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

2013-12-01

405

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

PubMed

An optical DNA biosensor based on fluorescence resonance energy transfer (FRET) utilizing synthesized quantum dot (QD) has been developed for the detection of specific-sequence of DNA for Ganoderma boninense, an oil palm pathogen. Modified QD that contained carboxylic groups was conjugated with a single-stranded DNA probe (ssDNA) via amide-linkage. Hybridization of the target DNA with conjugated QD-ssDNA and reporter probe labeled with Cy5 allows for the detection of related synthetic DNA sequence of Ganoderma boninense gene based on FRET signals. Detection of FRET emission before and after hybridization was confirmed through the capability of the system to produce FRET at 680 nm for hybridized sandwich with complementary target DNA. No FRET emission was observed for non-complementary system. Hybridization time, temperature and effect of different concentration of target DNA were studied in order to optimize the developed system. The developed biosensor has shown high sensitivity with detection limit of 3.55 × 10-9 M. TEM results show that the particle size of QD varies in the range between 5 to 8 nm after ligand modification and conjugation with ssDNA. This approach is capable of providing a simple, rapid and sensitive method for detection of related synthetic DNA sequence of Ganoderma boninense. PMID:25586416

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

2013-01-01

406

Efficient near-infrared organic light-emitting devices based on low-gap fluorescent oligomers  

NASA Astrophysics Data System (ADS)

We report efficient near-infrared (NIR) organic light-emitting devices (OLEDs) based on fluorescent donor-acceptor-donor conjugated oligomers. The energies of the highest occupied and lowest unoccupied molecular orbitals of these oligomers are controlled by the donor and acceptor components, respectively; hence the energy gap and therefore the emission wavelength can be tuned by changing the strengths of the donor and acceptor components. External quantum efficiencies (EQEs) up to 1.6% and power efficiencies up to 7.0 mW/W are achieved in NIR OLEDs based on 4,9-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-6,7-dimethyl-[1,2,5]thiadiazolo[3,4-g]-quinoxaline (BEDOT-TQMe2), in which the electroluminescence peaks at a wavelength of 692 nm but extends to well above 800 nm. With a stronger acceptor in the oligomer, 4,8-bis(2,3-dihydrothieno-[3,4-b][1,4]dioxin-5-yl)benzo[1,2-c;4,5-c']bis [1,2,5]thiadiazole (BEDOT-BBT) based devices show longer wavelength emission peaked at 815 nm, although the maximum EQE is reduced to 0.51% due to the lower fluorescent quantum yield of the NIR emitter. The efficiencies of these NIR OLEDs are further increased by two to three times by using the sensitized fluorescent device structure, leading to a maximum EQE of 3.1% for BEDOT-TQMe2 and 1.6% for BEDOT-BBT based devices.

Yang, Yixing; Farley, Richard T.; Steckler, Timothy T.; Eom, Sang-Hyun; Reynolds, John R.; Schanze, Kirk S.; Xue, Jiangeng

2009-08-01

407

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

408

Highly sensitive and selective fluorescent sensor for zinc ion based on a new diarylethene with a thiocarbamide unit.  

PubMed

A new photochromic diarylethene has been synthesized by using thiocarbamide as a functional group and perfluordiarylethene as photoswitching trigger via a salicylidene Schiff base linkage. The diarylethene could be used as a multicontrollable fluorescence switch when triggered by base/acid, light, and metal ions. The results showed that the absorption and fluorescence characteristics of the diarylethene exhibited sequence-dependent responses through efficient interaction of specific salicylidene Schiff base-linked thiocarbamide unit with tetrabutylammonium hydroxide/trifluoroacetic acid and photoirradiation. Moreover, the diarylethene was highly selective toward Zn(2+) ion with obvious fluorescence change from light blue to bright yellow in acetonitrile. The deprotonated form of the diarylethene had typical photochromism, but it showed an irreversible photocyclization reaction after binding with Zn(2+). Finally, two logic circuits were constructed by using the fluorescence intensity as the output signal with the inputs of the combinational stimuli of light and chemical species. PMID:25760313

Zhang, Congcong; Pu, Shouzhi; Sun, Zhiyuan; Fan, Congbin; Liu, Gang

2015-04-01

409

A turn-off fluorescent biosensor for the rapid and sensitive detection of uranyl ion based on molybdenum disulfide nanosheets and specific DNAzyme.  

PubMed

A novel fluorescent biosensor for detecting uranyl ion (UO2(2+)) in aqueous environment has been developed based on the specific recognition of DNAzyme and the fluorescence quenching ability of molybdenum disulfide (MoS2) nanosheets. The DNAzyme contains a DNA enzyme strand and a 6-carboxylfluorescein (FAM)-labeled DNA substrate strand. We demonstrated that MoS2 nanosheets have low affinity to the substrate-enzyme complex DNAzyme. Whereas, in the presence of UO2(2+), UO2(2+) can specifically cleave DNAzyme to release FAM-labeled single-strand DNA and the released FAM-labeled single-strand DNA can be firmly adsorbed on the surface of MoS2 nanosheets, which resulted in an obvious decrease of fluorescence intensity. This provided a sensing platform for the rapid, simple and sensitive fluorescent detection of UO2(2+). By using the sensing platform, a sensitive and selective fluorescent method for the rapid detection of UO2(2+) has been developed. In comparison with previous biosensor, the proposed method has obvious analytical advantage such as relatively high sensitivity and good stability, short analytical time and low cost. It can be used to detect as low as 2.14nM of UO2(2+) in aqueous environment with a recovery of 96-102% and a RSD<5% (n=6). The success of this study provides a promising alternative for the rapid and on-site detection of UO2(2+) in environmental monitoring. PMID:25797343

Zhang, HongYan; Ruan, YaJuan; Lin, Ling; Lin, Minggui; Zeng, Xiaoxue; Xi, Zhiming; Fu, FengFu

2015-07-01

410

A universal cloning method based on yeast homologous recombination that is simple, efficient, and versatile.  

PubMed

Cloning by homologous recombination (HR) in Saccharomyces cerevisiae is an extremely efficient and cost-effective alternative to other methods of recombinant DNA technologies. Unfortunately, it is incompatible with all the various specialized plasmids currently used in microbiology and biomedical research laboratories, and is therefore, not widely adopted. In an effort to dramatically improve the versatility of yeast gap-repair cloning and make it compatible with any DNA plasmid, we demonstrate that by simply including a yeast-cloning cassette (YCC) that contains the 2-micron origin of replication (2?m ori) and the ura3 gene for selection, multiple DNA fragments can be assembled into any DNA vector. We show this has almost unlimited potential by building a variety of plasmid for different uses including: recombinant protein production, epitope tagging, site-directed mutagenesis, and expression of fluorescent fusion proteins. We demonstrate the use in a variety of plasmids for use in microbial systems and even demonstrate it can be used in a vertebrate model. This method is remarkably simple and extremely efficient, plus it provides a significant cost saving over commercially available kits. PMID:24418681

Joska, Tammy M; Mashruwala, Ameya; Boyd, Jeffrey M; Belden, William J

2014-05-01

411

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

412

A fast and effective reconstruction method for fluorescence molecular tomography based on sparsity adaptive subspace pursuit  

NASA Astrophysics Data System (ADS)

Fluorescence molecular tomography (FMT), which is a promising tomographic method for in vivo small animal imaging, has many successful applications. However, FMT reconstruction is usually an ill-posed problem because only the photon distribution over the body surface is measurable. The Lp-norm regularization is generally adopted to stabilize the solution, which can be regarded as a type of a priori information of the fluorescent probe bio-distribution. When FMT is used for the early detection of tumors, an important feature is the sparsity of the fluorescent sources because tumors are usually very small and sparse at early stage. Considering this, we propose a fast and effective method with L1-norm based on sparsity adaptive subspace pursuit to solve the FMT problem in this paper. Our proposed method treats FMT problem with sparsity-promoting L1-norm as the basis pursuit problem. At each iteration, a sparsity factor that indicates the number of unknowns is estimated and updated adaptively. Then our method seeks a small index set which indicates atoms exhibiting highest correlation with the current residual, and updates the current supporting set by merging the newly selected index set. It can be regarded as a kind of sparse approximation reconstruction strategy. To evaluate our proposed method, we compare it to the iterated-shrinkage-based method with L1-norm regularization in numerical experiments. The results demonstrate that the proposed algorithm is able to obtain satisfactory reconstruction results. In addition, the proposed method is about two orders of magnitude faster compared to the iterated-shrinkage-based method. Our method is a practical and effective FMT reconstruction method.

Ye, Jinzuo; Chi, Chongwei; An, Yu; Xu, Han; Zhang, Shuang; Yang, Xin; Tian, Jie

2014-02-01

413

Simple Analytical and Graphical Methods for Carrier-Based PWM-VSI Drives  

Microsoft Academic Search

This paper provides analytical and graphical meth- ods for the study, performance evaluation, and design of the modern carrier-based pulsewidth modulators (PWM's), which are widely employed in PWM voltage-source inverter (VSI) drives. Simple techniques for generating the modulation waves of the high-performance PWM methods are described. The two most important modulator characteristics—the current ripple and the switching losses—are analytically modeled.

Ahmet M. Hava; Russel J. Kerkman; Thomas A. Lipo

1999-01-01

414

A Simple Streaming Media Transport Protocols Based on IPv6 QoS Mechanism  

Microsoft Academic Search

\\u000a The rapid growth of internet promotes evolution of network applications. As different network application has different set\\u000a of requirements for network technology, many protocols have been developed. Most of these protocols overlap and are redundant\\u000a in function, which result in lower performance. This paper presents an IPv6 QoS-based simple streaming transport protocol\\u000a (SSTP), which aims at next generation networks and

Yan Wei; Cheng Yuan; Ren Maosheng

2005-01-01

415

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

Microsoft Academic Search

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

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

2005-01-01

416

Synthesis and spectroscopic study of highly fluorescent ?-enaminone based boron complexes.  

PubMed

The newly synthesized 1, 1, 2-trimethyl-1H benzo[e]indoline based ?-enaminone boron complexes exhibited the intense fluorescence (Fmax=522-547nm) in solution as well as in solid state (Fmax=570-586nm). These complexes exhibited large stoke shift, excellent thermal and photo stability when compared to the boron dipyrromethene (BODIPY) colorants. Optimized geometry and orbital distribution in ground states were computed by employing density functional theory (DFT). The cyclic voltammetry study revealed the better electron transport ability of these molecules than current electroluminescent materials like tris(8-hydroxyquinoli-nato)-aluminium (Alq3) and BODIPY, which can find application in electroluminescent devices. PMID:25813165

Kumbhar, Haribhau S; Gadilohar, Balu L; Shankarling, Ganapati S

2015-07-01

417

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

418

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

419

Fluorescence Reporting Based on FRET Between Conjugated Polyelectrolyte and Organic Dye for Biosensor Applications  

Microsoft Academic Search

\\u000a \\u000a Abstract  Conjugated polyelectrolytes (CPEs), with highly delocalized electronic backbones and charged ionic side chains, are naturally\\u000a robust light-harvesting antenna for fluorescence resonance energy transfer (FRET) applications. This chapter describes FRET-based\\u000a biosensors using CPEs as energy donors from the viewpoint of sensing mechanism, donor–acceptor selection and detection targets.\\u000a Important information on how to design CPE structures and assay schemes is elucidated, and

Kan-Yi Pu; Bin Liu

420

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

421

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

PubMed

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

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

2015-03-01

422

Synchrotron based X-ray fluorescence activities at Indus-2: An overview  

NASA Astrophysics Data System (ADS)

X-Ray fluorescence (XRF) spectrometry is a powerful non-destructive technique for elemental analysis of materials at bulk and trace concentration levels. Taking into consideration several advantages of the synchrotron based XRF technique and to fulfill the requirements of Indian universities users we have setup a microfocus XRF beamline (BL-16) on Indus-2 synchrotron light source. The beamline offers a wide range of usages - both from research laboratories and industries; and for researchers working in diverse fields. A brief overview of the measured performance of the beamline, design specifications including various attractive features and recent research activities carried out on the BL-16 beamline are presented.

Tiwari, M. K.

2014-04-01

423

Electron transfer-based single molecule fluorescence as a probe for nano-environment dynamics.  

PubMed

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

424

A simple modern correctness condition for a space-based high-performance multiprocessor  

NASA Technical Reports Server (NTRS)

A number of U.S. national programs, including space-based detection of ballistic missile launches, envisage putting significant computing power into space. Given sufficient progress in low-power VLSI, multichip-module packaging and liquid-cooling technologies, we will see design of high-performance multiprocessors for individual satellites. In very high speed implementations, performance depends critically on tolerating large latencies in interprocessor communication; without latency tolerance, performance is limited by the vastly differing time scales in processor and data-memory modules, including interconnect times. The modern approach to tolerating remote-communication cost in scalable, shared-memory multiprocessors is to use a multithreaded architecture, and alter the semantics of shared memory slightly, at the price of forcing the programmer either to reason about program correctness in a relaxed consistency model or to agree to program in a constrained style. The literature on multiprocessor correctness conditions has become increasingly complex, and sometimes confusing, which may hinder its practical application. We propose a simple modern correctness condition for a high-performance, shared-memory multiprocessor; the correctness condition is based on a simple interface between the multiprocessor architecture and a high-performance, shared-memory multiprocessor; the correctness condition is based on a simple interface between the multiprocessor architecture and the parallel programming system.

Probst, David K.; Li, Hon F.

1992-01-01

425

Green fluorescent protein-based biosensor for detecting SOS-inducing activity of genotoxic compounds.  

PubMed

Increasing levels of environmental pollution demand specific and sensitive methods for detection of genotoxic agents in water, food products and environmental samples. Tests for genotoxicity assessment are often based on biosensor strains that respond to DNA damage induced by chemicals. In the present study, fluorescent reporter Escherichia coli strains have been developed, which contain a plasmid-borne transcriptional fusion between the DNA-damage inducible recA promoter and the green fluorescent protein gene (gfp) or a gene encoding a red-shifted, higher intensity GFP variant (mutant 3). GFP-based biosensors allowed the detection of a dose-dependent response to genotoxic agents such as mitomycin C (MMC), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and nalidixic acid (NA). A reporter strain carrying recA'-gfp mutant 3 fusion gave more dramatic and sensitive response than a strain containing the wild-type gfp. These results indicate that recA'-gfp mutant 3-based biosensor is potentially useful for detection of genotoxins. PMID:11733081

Kostrzynska, Magdalena; Leung, Kam T; Lee, Hung; Trevors, Jack T

2002-01-01

426

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

PubMed

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

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

2015-05-15

427

High-throughput fluorescent-based NKCC functional assay in adherent epithelial cells  

PubMed Central

Background The kidney-specific NKCC cotransporter isoform NKCC2 is involved in the Na+ reabsorption in the Thich Ascending Limb (TAL) cells and in the regulation of body fluid volume. In contrast, the isoform NKCC1 represents the major pathway for Cl- entry in endothelial cells, playing a crucial role in cell volume regulation and vascular tone. Importantly, both NKCC isoforms are involved in the regulation of blood pressure and represent important potential drug targets for the treatment of hypertension. Results Taking advantage of an existing Thallium (Tl+)-based kit, we set up a Tl+ influx-based fluorescent assay, that can accurately and rapidly measure NKCC transporter activity in adherent epithelial cells using the high-throughput Flex station device. We assessed the feasibility of this assay in the renal epithelial LLC-PK1 cells stably transfected with a previously characterized chimeric NKCC2 construct (c-NKCC2). We demonstrated that the assay is highly reproducible, offers high temporal resolution of NKCC-mediated ion flux profiles and, importantly, being a continuous assay, it offers improved sensitivity over previous endpoint NKCC functional assays. Conclusions So far the screening of NKCC transporters activity has been done by 86Rb+ influx assays. Indeed, a fluorescence-based high-throughput screening method for testing NKCC inhibitors would be extremely useful in the development and characterization of new anti-hypertensive drugs. PMID:23506056

2013-01-01

428

A fluorescence-based high throughput assay for the determination of small molecule–human serum albumin protein binding  

PubMed Central

Herein, we describe the development of a fluorescence-based high throughput assay to determine the small molecule binding towards human serum albumin (HSA). This innovative competition assay is based on the use of a novel fluorescent small molecule Red Mega 500 with unique spectroscopic and binding properties. The commercially available probe displays a large fluorescence intensity difference between the protein-bound and protein-unbound state. The competition of small molecules for HSA binding in the presence of probe resulted in low fluorescence intensities. The assay was evaluated with the LOPAC small molecule library of 1280 compounds identifying known high protein binders. The small molecule competition of HSA–Red Mega 500 binding was saturable at higher compound concentrations and exhibited IC50 values between 3–24 ?M. The compound affinity towards HSA was confirmed by isothermal titration calorimetry indicating that the new protein binding assay is a valid high throughput assay to determine plasma protein binding. PMID:24390461

McCallum, Megan M.; Pawlak, Alan J.; Shadrick, William R.; Simeonov, Anton; Jadhav, Ajit; Yasgar, Adam; Maloney, David J.; Arnold, Leggy A.

2014-01-01

429

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

430

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

431

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

432

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

PubMed

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

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

2010-10-01

433

A novel device based on a fluorescent cross-responsive sensor array for detecting lung cancer related volatile organic compounds.  

PubMed

In this paper, a novel, simple, rapid, and low-cost detection device for lung cancer related Volatile Organic Compounds (VOCs) was constructed. For this task, a sensor array based on cross-responsive mechanism was designed. A special gas chamber was made to insure sensor array exposed to VOCs sufficiently and evenly, and FLUENT software was used to simulate the performance of the gas chamber. The data collection and processing system was used to detect fluorescent changes of the sensor arrays before and after reaction, and to extract unique patterns of the tested VOCs. Four selected VOCs, p-xylene, styrene, isoprene, and hexanal, were detected by the proposed device. Unsupervised pattern recognition methods, hierarchical cluster analysis and principal component analysis, were used to analyze data. The results showed that the methods could 100% discriminate the four VOCs. What is more, combined with artificial neural network, the correct rate of quantitative detection was up to 100%, and the device obtained responses at concentrations below 50 ppb. In conclusion, the proposed detection device showed excellent selectivity and discrimination ability for the VOCs related to lung cancer. Furthermore, our preliminary study demonstrated that the proposed detection device has brilliant potential application for early clinical diagnosis of lung cancer. PMID:25725887

Lei, Jin-Can; Hou, Chang-Jun; Huo, Dan-Qun; Luo, Xiao-Gang; Bao, Ming-Ze; Li, Xian; Yang, Mei; Fa, Huan-Bao

2015-02-01

434

A novel device based on a fluorescent cross-responsive sensor array for detecting lung cancer related volatile organic compounds  

NASA Astrophysics Data System (ADS)

In this paper, a novel, simple, rapid, and low-cost detection device for lung cancer related Volatile Organic Compounds (VOCs) was constructed. For this task, a sensor array based on cross-responsive mechanism was designed. A special gas chamber was made to insure sensor array exposed to VOCs sufficiently and evenly, and FLUENT software was used to simulate the performance of the gas chamber. The data collection and processing system was used to detect fluorescent changes of the sensor arrays before and after reaction, and to extract unique patterns of the tested VOCs. Four selected VOCs, p-xylene, styrene, isoprene, and hexanal, were detected by the proposed device. Unsupervised pattern recognition methods, hierarchical cluster analysis and