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Sample records for biosynthesis fluorescence polarization

  1. Fluorescence confocal polarizing microscopy

    Indian Academy of Sciences (India)

    Much of the modern understanding of orientational order in liquid crystals (LCs) is based on polarizing microscopy (PM). A PM image bears only two-dimensional (2D) information, integrating the 3D pattern of optical birefringence over the path of light. Recently, we proposed a technique to image 3D director patterns by ...

  2. [Fluorescence polarization immunoassay of ractopamine].

    Science.gov (United States)

    Zvereva, E A; Shpakova, N A; Zherdev, A V; Kiu, L; Xu, C; Eremin, S A; Dzantiev, B B

    2016-01-01

    A technique was developed for fluorescence polarization immunoassay (FPIA) of ractopamine, a toxic low molecular weight nonsteroidal growth regulator belonging to the most controlled contaminants of food products of animal origin. The assay is based on the competition between a sample containing ractopamine and ractopamine–fluorophore conjugate for binding to antibodies. The competition is monitored via changes in the degree of fluorescence polarization for plane-polarized excitation light, which differs for the free and antibody-bound forms of the conjugate. The optimal assay conditions were established, ensuring a high accuracy and minimal detection limit. The developed assay demonstrated a detection limit of 1 ng/mL and a range of detectable concentrations of 2.3–50 ng/mL, which met the requirements of sanitary control. The duration of the analysis was 10 min. The possible application of the developed FPIA was demonstrated with testing of turkey meat. The speed and simplicity of the proposed assay define its efficiency as a screening tool for safety of foods.

  3. Macromolecule biosynthesis assay and fluorescence spectroscopy methods to explore antimicrobial peptide mode(s) of action

    DEFF Research Database (Denmark)

    Jana, Bimal; Baker, Kristin Renee; Guardabassi, Luca

    2017-01-01

    the biosynthesis rate of macromolecules (e.g., DNA, RNA, protein, and cell wall) and the cytoplasmic membrane proton motive force (PMF) energy can help to unravel the diverse modes of action of AMPs. Here, we present an overview of macromolecule biosynthesis rate measurement and fluorescence spectroscopy methods...

  4. Polarization of fluorescence: a probe of molecular autoionization

    International Nuclear Information System (INIS)

    Leroi, G.E.; Dehmer, J.L.; Parr, A.C.; Poliakoff, E.D.

    1983-01-01

    The polarization of fluorescence from excited-state molecular photoions provides a direct probe of the photoionization dynamics and the symmetry signatures of autoionizing resonances. Measurements on CO 2 and CS 2 are presented as examples

  5. Hybrid fluorescent layer emitting polarized light

    Directory of Open Access Journals (Sweden)

    Mohammad Mohammadimasoudi

    2017-07-01

    Full Text Available Semiconductor nanorods have anisotropic absorption and emission properties. In this work a hybrid luminescent layer is produced based on a mixture of CdSe/CdS nanorods dispersed in a liquid crystal that is aligned by an electric field and polymerized by UV illumination. The film emits light with polarization ratio 0.6 (polarization contrast 4:1. Clusters of nanorods in liquid crystal can be avoided by applying an AC electric field with sufficient amplitude. This method can be made compatible with large-scale processing on flexible transparent substrates. Thin polarized light emitters can be used in LCD backlights or solar concentrators to increase the efficiency.

  6. Fluorescence confocal polarizing microscopy: Three-dimensional ...

    Indian Academy of Sciences (India)

    Much of the modern understanding of orientational order in liquid crystals (LCs) is based on polarizing microscopy (PM). A PM image bears only two-dimensional (2D) information, integrating the 3D pattern of optical birefringence over the path of light. Recently, we proposed a technique to image 3D director patterns by ...

  7. Fluorescence confocal polarizing microscopy: Three-dimensional ...

    Indian Academy of Sciences (India)

    Abstract. Much of the modern understanding of orientational order in liquid crystals (LCs) is based on polarizing microscopy (PM). A PM image bears only two-dimensional (2D) information, integrating the 3D pattern of optical birefringence over the path of light. Recently, we proposed a technique to image 3D director ...

  8. Fluorescence confocal polarizing microscopy: Three-dimensional ...

    Indian Academy of Sciences (India)

    cholesterics, polarization of both ordinary and extraordinary waves follows the local director (the so-called Mauguin regime) [28]. This effect must be taken into account while interpreting the FCPM images for samples with twist deformations, especially when the twist scale is supra-micron and light propagates along the twist ...

  9. Polarized front-face fluorescence for muscle tissue structure evaluation

    Science.gov (United States)

    Luc, C.; Clerjon, S.; Peyrin, F.; Lepetit, J.

    2008-05-01

    The fluorescence anisotropy of a rigid medium is a consequence of photoselection of fluorophores and their orientations. This makes it possible to use polarized front-face fluorescence to provide structural information on biological tissues like muscle. Tryptophan is the major intrinsic fluorophore in muscle. It is embedded in proteins which act as building blocks for muscle structuration because of their preferential alignment. Our working hypothesis is that when the arrangement of the proteins changes, there are concomitant changes in fluorescence anisotropy parameters. Our research is directed toward evaluating muscle structure and its evolution post mortem. We report a theoretical simple model of tryptophan fluorescence and an experimental method to measure the fluorescence anisotropy of biological opaque tissues. Instrumental and optical considerations have to be taken into account in experiments on front-face polarization to make certain of measurement accuracy. Therefore, we present a detailed report on the adjustments and corrections made on a conventional L-spectrofluorimeter to adapt it to fluorescence anisotropy measurements on biological tissues. Data from several experiments demonstrate how the method is able to show muscle structure modifications. We show how it is possible to fit experimental data with the model developed in order to obtain structural information.

  10. Analysis of Septin Reorganization at Cytokinesis Using Polarized Fluorescence Microscopy

    Directory of Open Access Journals (Sweden)

    Molly McQuilken

    2017-05-01

    Full Text Available Septins are conserved filament-forming proteins that act in diverse cellular processes. They closely associate with membranes and, in some systems, components of the cytoskeleton. It is not well understood how filaments assemble into higher-order structures in vivo or how they are remodeled throughout the cell cycle. In the budding yeast S. cerevisiae, septins are found through most of the cell cycle in an hourglass organization at the mother-bud neck until cytokinesis when the collar splits into two rings that disassemble prior to the next cell cycle. Experiments using polarized fluorescence microscopy have suggested that septins are arranged in ordered, paired filaments in the hourglass and undergo a coordinated 90° reorientation during splitting at cytokinesis. This apparent reorganization could be due to two orthogonal populations of filaments disassembling and reassembling or being preferentially retained at cytokinesis. In support of this idea, we report a decrease in septin concentration at the mother-bud neck during cytokinesis consistent with other reports and the timing of the decrease depends on known septin regulators including the Gin4 kinase. We took a candidate-based approach to examine what factors control reorientation during splitting and used polarized fluorescence microscopy to screen mutant yeast strains deficient in septin interacting proteins. Using this method, we have linked known septin regulators to different aspects of the assembly, stability, and reorganization of septin assemblies. The data support that ring splitting requires Gin4 activity and an anillin-like protein Bud4, and normal accumulation of septins at the ring requires phosphorylation of Shs1. We found distinct regulatory requirements for septin organization in the hourglass compared to split rings. We propose that septin subpopulations can vary in their localization and assembly/disassembly behavior in a cell-cycle dependent manner at cytokinesis.

  11. Screening for Antifibrotic Compounds Using High Throughput System Based on Fluorescence Polarization

    Directory of Open Access Journals (Sweden)

    Branko Stefanovic

    2014-04-01

    Full Text Available Fibroproliferative diseases are one of the leading causes of death worldwide. They are characterized by reactive fibrosis caused by uncontrolled synthesis of type I collagen. There is no cure for fibrosis and development of therapeutics that can inhibit collagen synthesis is urgently needed. Collagen α1(I mRNA and α2(I mRNA encode for type I collagen and they have a unique 5' stem-loop structure in their 5' untranslated regions (5'SL. Collagen 5'SL binds protein LARP6 with high affinity and specificity. The interaction between LARP6 and the 5'SL is critical for biosynthesis of type I collagen and development of fibrosis in vivo. Therefore, this interaction represents is an ideal target to develop antifibrotic drugs. A high throughput system to screen for chemical compounds that can dissociate LARP6 from 5'SL has been developed. It is based on fluorescence polarization and can be adapted to screen for inhibitors of other protein-RNA interactions. Screening of 50,000 chemical compounds yielded a lead compound that can inhibit type I collagen synthesis at nanomolar concentrations. The development, characteristics, and critical appraisal of this assay are presented.

  12. Diagnosis of bovine brucellosis using a homogeneous fluorescence polarization assay.

    Science.gov (United States)

    Nielsen, K; Gall, D; Lin, M; Massangill, C; Samartino, L; Perez, B; Coats, M; Hennager, S; Dajer, A; Nicoletti, P; Thomas, F

    1998-12-11

    To evaluate the fluorescence polarization assay (FPA) for the serological diagnosis of bovine brucellosis, 118 sera from cattle which were culture positive for Brucella abortus, 1751 sera from cattle from premises containing cattle infected with B. abortus, 1222 sera from cattle vaccinated with B. abortus strain 19 and 1199 sera from cattle with no evidence of brucellosis were tested in Argentina, Chile, Mexico and in the American states of Iowa, Missouri and Texas. Initial determination of serological positivity and negativity was based upon reactivity in currently used serological tests, consisting of a rapid screening test, the rose-bengal or the buffered plate antigen tests, followed by a second serological test, the complement fixation test. Sensitivity of the FPA (sera from culture positive animals) ranged from 87.5% to 100%. Serological positivity of cattle from infected premises ranged from 65.5% to 99.0% while the % negative cattle in herds without evidence of brucellosis was between 94.9 and 100%. Of B. abortus strain 19 vaccinated cattle which were positive in at least one in-use serological tests, 88.2% were negative in the FPA. In contrast, previous Canadian studies, sensitivity values were 99.0% and 100% and the specificity in both cases was 100%. This discrepancy was probably due to the use of less well characterized sera in the current study.

  13. Polarization contrast in fluorescence scanning near-field optical microscopy in reflection

    NARCIS (Netherlands)

    Jalocha, A.; Jalocha, A.; van Hulst, N.F.

    1995-01-01

    Polarization contrast is presented in fluorescence images of a Langmuir-Blodgett monolayer obtained with a scanning near-field optical microscope operated in reflection. A tapered optical fiber is used both to excite and to collect the fluorescence. The lateral resolution in the reflection

  14. Ultrafast polarized fluorescence measurements on tryptophan and a tryptophan-containing peptide

    NARCIS (Netherlands)

    Larsen, O.F.A.; van Stokkum, I.H.M.; Pandit, A.; van Grondelle, R.; van Amerongen, H.

    2003-01-01

    In this work polarized picosecond fluorescence measurements were performed on isolated tryptophan and tryptophan in a small 22-mer peptide using a streak camera coupled to a spectrograph as a detection system. In both cases the fluorescence decay was multiexponential with decay times of ∼500 ps and

  15. Ultrafast polarized fluorescence measurements on Tryptophan and a Tryptophan-containing peptide

    NARCIS (Netherlands)

    Larsen, O.F.A.; Stokkum, van I.H.M.; Pandit, A.; Grondelle, van R.; Amerongen, van H.

    2003-01-01

    In this work polarized picosecond fluorescence measurements were performed on isolated tryptophan and tryptophan in a small 22-mer peptide using a streak camera coupled to a spectrograph as a detection system. In both cases the fluorescence decay was multiexponential with decay times of similar

  16. Chlorophyll fluorescence extraction from water-leaving radiance of algae-containing water through polarization

    Science.gov (United States)

    Wang, Lin; Qiu, Zhongfeng; Pang, Huifang; Liu, Yongjian; Chen, Yanlong; Jiang, Lingling

    2017-12-01

    When measuring reflectance spectra, it is very important to accurately extract chlorophyll fluorescence from elastic- scattering light in water-leaving radiance. The elastic scattering of light by water particles produces partially polarized light. In contrast, chlorophyll fluorescence in planktonic algae yields completely unpolarized light. These properties can be used to separate fluorescent signals from the water-leaving radiance and thus to determine chlorophyll concentration. The algal species Aureococcus anophagefferens was used to conduct a laboratory polarization experiment. For the tests, we used a field spectroradiometer and a polarizer; measurements were collected using two different observation modes. The chlorophyll fluorescence curve extracted through polarization shows an excellent match with the results obtained using the fluorospectro photometer for both measurement modes, suggesting that polarization-based chlorophyll fluorescence extraction may be feasible. The extracted fluorescence is more reliable at incident zenith angles ranging from 30° to 60°. For algae-containing water, the results improve with increasing chlorophyll concentration. This method could help improve chlorophyll concentration measurement and the remote-sensing detection of resulting harmful algae blooms.

  17. Fluorescence polarization of tetracycline derivatives as a technique for mapping nonmelanoma skin cancers.

    Science.gov (United States)

    Yaroslavsky, Anna N; Salomatina, Elena V; Neel, Victor; Anderson, Rox; Flotte, Thomas

    2007-01-01

    Nonmelanoma skin cancer is the most common form of human cancer, often resulting in high morbidity. Low visual contrast of these tumors makes their delineation a challenging problem. Employing a linearly polarized monochromatic light source and a wide-field CCD camera, we have developed a technique for fluorescence polarization imaging of the nonmelanoma cancers stained using antibiotics from the tetracycline family. To determine the feasibility of the method, fluorescence polarization images of 86 thick, fresh cancer excisions were studied. We found that the level of endogenous fluorescence polarization was much lower than that of exogenous, and that the average values of fluorescence polarization of tetracycline derivatives were significantly higher in cancerous as compared to normal tissue. Out of 86 tumors [54 stained in demeclocycline (DMN) and 32 in tetracycline (TCN)], in 79 cases (51-DMN, 28-TCN) the location, size, and shape of the lesions were identified accurately. The results of this trial indicate that nonmelanoma skin tumors can be distinguished from healthy tissue based on the differences in exogenous fluorescence polarization of TCN and/or DMN. Therefore, the developed technique can provide an important new tool for image-guided cancer surgery.

  18. Oral cancer detection based on fluorescence polarization of blood plasma at excitation wavelength 405 nm

    Science.gov (United States)

    Pachaiappan, Rekha; Prakasarao, Aruna; Manoharan, Yuvaraj; Dornadula, Koteeswaran; Singaravelu, Ganesan

    2017-02-01

    During metabolism the metabolites such as hormones, proteins and enzymes were released in to the blood stream by the cells. These metabolites reflect any change that occurs due to any disturbances in normal metabolic function of the human system. This was well observed with the altered spectral signatures observed with fluorescence spectroscopic technique. Previously many have reported on the significance of native fluorescence spectroscopic method in the diagnosis of cancer. As fluorescence spectroscopy is sensitive and simple, it has complementary techniques such as excitation-emission matrix, synchronous and polarization. The fluorescence polarization measurement provides details about any association or binding reactions and denaturing effects that occurs due to change in the micro environment of cells and tissues. In this study, we have made an attempt in the diagnosis of oral cancer at 405 nm excitation using fluorescence polarization measurement. The fluorescence anisotropic values calculated from polarized fluorescence spectral data of normal and oral cancer subjects yielded a good accuracy when analyzed with linear discriminant analysis based artificial neural network. The results will be discussed in detail.

  19. Effect of PAF on polyrnorphonuclear leucocyte plasma membrane polarity: a fluorescence study

    Directory of Open Access Journals (Sweden)

    A. Kantar

    1993-01-01

    Full Text Available The effect of PAF on the plasma membrane polarity of polymorphonuclear leukocytes (PMNs was investigated by measuring the steady-state fluorescence emission spectra of 2-dimethylamino(6-1auroyl naphthalene (Laurdan, which is known to be incorporated at the hydrophobic-hydrophilic interface of the bilayer, displaying spectral sensitivity to the polarity of its surrounding. Laurdan shows a marked steady-state emission blue-shift in non-polar solvents, with respect to polar solvents. Our results demonstrate that PAF (10−7 M induces a blue shift of the fluorescence emission spectra of Laurdan. These changes are blocked in the presence of the PAF antagonist, L-659,989. Our data indicate that the interaction between PAF and PMNs is accompanied by a decrease in polarity in the hydrophobic-hydrophilic interface of the plasma membrane.

  20. The fast polarization modulation based dualfocus fluorescence correlation spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Štefl, Martin; Benda, Aleš; Gregor, I.; Hof, Martin

    2014-01-01

    Roč. 22, č. 1 (2014), s. 885-899 ISSN 1094-4087 R&D Projects: GA AV ČR KJB400400904; GA ČR GBP208/12/G016 Institutional support: RVO:61388955 Keywords : spectroscopy * fluorescence and luminiscence * confocal microscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.488, year: 2014

  1. Determination of deoxynivalenol in wheat bran and whole-wheat flour by fluorescence polarization immunoassay

    Science.gov (United States)

    A rapid and accurate fluorescence polarization (FP) immunoassay has been optimized for the determination of deoxynivalenol (DON) in bran and whole-wheat flour. A preliminary treatment with activated charcoal was used to eliminate the strong matrix effect due to highly colored interfering compounds p...

  2. New applications of fluorescence polarization for enzyme assays and in genomics

    Science.gov (United States)

    Nikiforov, Theo; Coffin, Jill; Jeong, Sang; Simeonov, Anton; Bi, Xiahui

    2001-05-01

    We have developed new, fluorescence polarization-based approaches for performing enzyme assays in homogeneous solutions and for detecting the hybridization of peptide nucleic acids to DNA targets. In the first method, fluorescein-labeled peptides serving as protein kinase sustrates are thiophosphorylated in the presence of the ATP analog ATPγS. A sulfer-reactive biotin derivative is then added to the mixture and allowed to react with the thiophosphorylated peptide. The formation of a fluorescein-labeled, biotinylated product can be detected by measuring the fluorescence polarization signal of fluorescein upon addition of streptavidin. In the second method, fluorescein-labeled peptides are subjected to enzymatic phosphorylation, desphosphorlation, or proteollytic cleavage by protein kinases, phosphatases, and proteases. The differential binding of the enzymatic substrates and products to cationic polymers such as polyaraginine can be conveniently measured by fluorescence polarization. Finally, we have discovered that the process of hybridization of peptide nucleic acid probes (PNAs) to their target DNA molecules can be followed by measuring the fluorescence polarization of a fluorophore attached to the PNA probes. These measurements can be done either in the presence or absence of polylysine in solution. Examples of the application of this method for single nucleotide polymorphism (SNP) typing are presented.

  3. A Fluorescence Polarization Assay To Detect Steroid Hormone Traces in Milk.

    Science.gov (United States)

    Varriale, Antonio; Pennacchio, Anna; Pinto, Gabriella; Oliviero, Giorgia; D'Errico, Stefano; Majoli, Adelia; Scala, Andrea; Capo, Alessandro; Pennacchio, Angela; Di Giovanni, Stefano; Staiano, Maria; D'Auria, Sabato

    2015-10-21

    Steroids are a class of hormones improperly used in livestock as growth-promoting agents. Due to their high risk for human health, the European Union (EU) has strictly forbidden the administration of all natural and synthetic steroid hormones to food-producing animals, and the development of new rapid detection methods are greatly encouraged. This work reports a novel fluorescence polarization assay, ready to use, capable of detecting 17β-estradiol directly in milk samples with a low limit of detection of <10 pmol. It is based on the coupling of monospecific antibodies against 17β-estradiol and fluorophores, capable of modulating the fluorescence polarization emission on the basis of the specific binding of antibodies to fluorescence-labeled 17β-estradiol derivative. The successful detection of 17β-estradiol has disclosed the development of an efficient method, easily extensible to any food matrix and having the potential to become a milestone in food quality and safety.

  4. Ratiometric fluorescence polarization as a cytometric functional parameter: theory and practice

    Energy Technology Data Exchange (ETDEWEB)

    Yishai, Yitzhak; Fixler, Dror; Cohen-Kashi, Meir; Zurgil, Naomi; Deutsch, Mordechai [The Biophysical Interdisciplinary Jerome Schottenstein Center for the Research and the Technology of the Cellome, Department of Physics, Bar-Ilan University, Ramat-Gan 52900 (Israel)

    2003-08-07

    The use of ratiometric fluorescence polarization (RFP) as a functional parameter in monitoring cellular activation is suggested, based on the physical phenomenon of fluorescence polarization dependency on emission wavelengths in multiple (at least binary) solutions. The theoretical basis of this dependency is thoroughly discussed and examined via simulation. For simulation, aimed to imitate a fluorophore-stained cell, real values of the fluorescence spectrum and polarization of different single fluorophore solutions were used. The simulation as well as the experimentally obtained values of RFP indicated the high sensitivity of this measure. Finally, the RFP parameter was utilized as a cytometric measure in three exemplary cellular bioassays. In the first, the apoptotic effect of oxLDL in a human Jurkat FDA-stained T cell line was monitored by RFP. In the second, the interaction between cell surface membrane receptors of human T lymphocyte cells was monitored by RFP measurements as a complementary means to the fluorescence resonance energy transfer (FRET) technique. In the third bioassay, cellular thiol level of FDA- and CMFDA-labelled Jurkat T cells was monitored via RFP.

  5. Maximum entropy analysis of polarized fluorescence decay of (E)GFP in aqueous solution

    Science.gov (United States)

    Novikov, Eugene G.; Skakun, Victor V.; Borst, Jan Willem; Visser, Antonie J. W. G.

    2018-01-01

    The maximum entropy method (MEM) was used for the analysis of polarized fluorescence decays of enhanced green fluorescent protein (EGFP) in buffered water/glycerol mixtures, obtained with time-correlated single-photon counting (Visser et al 2016 Methods Appl. Fluoresc. 4 035002). To this end, we used a general-purpose software module of MEM that was earlier developed to analyze (complex) laser photolysis kinetics of ligand rebinding reactions in oxygen binding proteins. We demonstrate that the MEM software provides reliable results and is easy to use for the analysis of both total fluorescence decay and fluorescence anisotropy decay of aqueous solutions of EGFP. The rotational correlation times of EGFP in water/glycerol mixtures, obtained by MEM as maxima of the correlation-time distributions, are identical to the single correlation times determined by global analysis of parallel and perpendicular polarized decay components. The MEM software is also able to determine homo-FRET in another dimeric GFP, for which the transfer correlation time is an order of magnitude shorter than the rotational correlation time. One important advantage utilizing MEM analysis is that no initial guesses of parameters are required, since MEM is able to select the least correlated solution from the feasible set of solutions.

  6. Polarization-dependent responses of fluorescent indicators partitioned into myelinated axons

    Science.gov (United States)

    Micu, Ileana; Brideau, Craig; Stys, Peter K.

    2012-02-01

    Myelination, i.e. the wrapping of axons in multiple layers of lipid-rich membrane, is a unique phenomenon in the nervous systems of both vertebrates and invertebrates, that greatly increases the speed and efficiency of signal transmission. In turn, disruption of axo-myelinic integrity underlies disability in numerous clinical disorders. The dependence of myelin physiology on nanometric organization of its lamellae makes it difficult to accurately study this structure in the living state. We expected that fluorescent probes might become highly oriented when partitioned into the myelin sheath, and in turn, this anisotropy could be interrogated by controlling the polarization state of the exciting laser field used for 2-photon excited fluorescence (TPEF). Live ex vivo myelinated rodent axons were labeled with a series of lipohilic and hydrophilic fluorescenct probes, and TPEF images acquired while laser polarization was varied at the sample over a broad range of ellipticities and orientations of the major angle [see Brideau, Micu & Stys, abstract this meeting]. We found that most probes exhibited strong dependence on both the major angle of polarization, and perhaps more surprisingly, on ellipticity as well. Lipophilic vs. hydrophilic probes exhibited distinctly different behavior. We propose that polarization-dependent TPEF microscopy represents a powerful tool for probing the nanostructural architecture of both myelin and axonal cytoskeleton in a domain far below the resolution limit of visible light microscopy. By selecting probes with different sizes and physicochemical properties, distinct aspects of cellular nanoarchitecture can be accurately interrogated in real-time in living tissue.

  7. Detection of 13,19-didesmethyl C spirolide by fluorescence polarization using Torpedo electrocyte membranes.

    Science.gov (United States)

    Fonfría, Eva S; Vilariño, Natalia; Molgó, Jordi; Aráoz, Rómulo; Otero, Paz; Espiña, Begoña; Louzao, M Carmen; Alvarez, Mercedes; Botana, Luis M

    2010-08-01

    Fluorescence polarization (FP) is a powerful tool for studying molecular interactions by monitoring changes in the apparent size of fluorescent molecules. In this paper, a previously described fluorescence polarization assay was used to detect 13,19-didesmethyl C spirolide. The assay is based on the competition of cyclic imine marine biotoxins with alpha-bungarotoxin for binding to nicotinic acetylcholine receptor-enriched membranes of Torpedo marmorata. The 13,19-didesmethyl C spirolide was detected in buffer and mussel matrix. The sensitivity of the assay for the 13,19-didesmethyl C spirolide and the 13-desmethyl C spirolide was similar. After an acetone/chloroform extraction of spiked mussel meat, the average recovery rate of 13,19-didesmethyl C spirolide was 77.7 +/- 1.9%. The quantification range for this toxin in mussel was 40-200 microg/kg of shellfish meat. This assay can be used to detect the spirolides 13,19-didesmethyl C spirolide and 13-desmethyl C spirolide, in shellfish as a screening assay. Copyright 2010 Elsevier Inc. All rights reserved.

  8. A rate-equation model for polarized laser-induced fluorescence to measure electric field in glow discharge He plasmas

    International Nuclear Information System (INIS)

    Takiyama, K.; Watanabe, M.; Oda, T.

    1998-01-01

    Possibility of applying polarized laser-induced fluorescence (LIF) spectroscopy for measuring the electric field in a plasma with a large collisional depolarization has been investigated. A rate equation model including the depolarization process was employed to analyze the time evolution of LIF polarization components. The polarized LIF pulse shapes observed in the sheath of a He glow discharge plasma were successfully reproduced, and the electric field distribution was obtained with high accuracy. (author)

  9. Biosynthesis of CdS nanoparticles: A fluorescent sensor for sulfate-reducing bacteria detection.

    Science.gov (United States)

    Qi, Peng; Zhang, Dun; Zeng, Yan; Wan, Yi

    2016-01-15

    CdS nanoparticles were synthesized with an environmentally friendly method by taking advantage of the characteristic metabolic process of sulfate-reducing bacteria (SRB), and used as fluorescence labels for SRB detection. The presence of CdS nanoparticles was observed within and immediately surrounded bacterial cells, indicating CdS nanoparticles were synthesized both intracellularly and extracellularly. Moreover, fluorescent properties of microbial synthesized CdS nanoparticles were evaluated for SRB detection, and a linear relationship between fluorescence intensity and the logarithm of bacterial concentration was obtained in the range of from 1.0×10(2) to 1.0×10(7)cfu mL(-1). The proposed SRB detection method avoided the use of biological bio-recognition elements which are easy to lose their specific recognizing abilities, and the bacterial detection time was greatly shortened compared with the widely used MPN method which would take up to 15 days to accomplish the detection process. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Fluorescence polarization study of lipids and membranes prepared from brain hemispheres of a hibernating mammal.

    Science.gov (United States)

    Montaudon, D; Robert, J; Canguilhem, B

    1984-02-29

    The physical behavior of total lipids, microsomes and microsomal lipids prepared from brain hemispheres of European Hamsters (Cricetus cricetus) was approached by the measure of the fluorescence polarization of the probe 1,6-diphenyl 1,3,5-hexatriene. We compare in this study the results obtained for two critical periods for a hibernator: winter (torpid state) and summer (active state). An increase in fluidity was noticed in the winter lipid and membrane preparations. The difference was however of very low magnitude, suggesting that only the microenvironment of some proteins was involved, rather than the bulk membrane fluidity.

  11. Identification of adiponectin receptor agonist utilizing a fluorescence polarization based high throughput assay.

    Directory of Open Access Journals (Sweden)

    Yiyi Sun

    Full Text Available Adiponectin, the adipose-derived hormone, plays an important role in the suppression of metabolic disorders that can result in type 2 diabetes, obesity, and atherosclerosis. It has been shown that up-regulation of adiponectin or adiponectin receptor has a number of therapeutic benefits. Given that it is hard to convert the full size adiponectin protein into a viable drug, adiponectin receptor agonists could be designed or identified using high-throughput screening. Here, we report on the development of a two-step screening process to identify adiponectin agonists. First step, we developed a high throughput screening assay based on fluorescence polarization to identify adiponectin ligands. The fluorescence polarization assay reported here could be adapted to screening against larger small molecular compound libraries. A natural product library containing 10,000 compounds was screened and 9 hits were selected for validation. These compounds have been taken for the second-step in vitro tests to confirm their agonistic activity. The most active adiponectin receptor 1 agonists are matairesinol, arctiin, (--arctigenin and gramine. The most active adiponectin receptor 2 agonists are parthenolide, taxifoliol, deoxyschizandrin, and syringin. These compounds may be useful drug candidates for hypoadiponectin related diseases.

  12. A sensitive fluorescent probe for the polar solvation dynamics at protein-surfactant interfaces.

    Science.gov (United States)

    Singh, Priya; Choudhury, Susobhan; Singha, Subhankar; Jun, Yongwoong; Chakraborty, Sandipan; Sengupta, Jhimli; Das, Ranjan; Ahn, Kyo-Han; Pal, Samir Kumar

    2017-05-17

    Relaxation dynamics at the surface of biologically important macromolecules is important taking into account their functionality in molecular recognition. Over the years it has been shown that the solvation dynamics of a fluorescent probe at biomolecular surfaces and interfaces account for the relaxation dynamics of polar residues and associated water molecules. However, the sensitivity of the dynamics depends largely on the localization and exposure of the probe. For noncovalent fluorescent probes, localization at the region of interest in addition to surface exposure is an added challenge compared to the covalently attached probes at the biological interfaces. Here we have used a synthesized donor-acceptor type dipolar fluorophore, 6-acetyl-(2-((4-hydroxycyclohexyl)(methyl)amino)naphthalene) (ACYMAN), for the investigation of the solvation dynamics of a model protein-surfactant interface. A significant structural rearrangement of a model histone protein (H1) upon interaction with anionic surfactant sodium dodecyl sulphate (SDS) as revealed from the circular dichroism (CD) studies is nicely corroborated in the solvation dynamics of the probe at the interface. The polarization gated fluorescence anisotropy of the probe compared to that at the SDS micellar surface clearly reveals the localization of the probe at the protein-surfactant interface. We have also compared the sensitivity of ACYMAN with other solvation probes including coumarin 500 (C500) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM). In comparison to ACYMAN, both C500 and DCM fail to probe the interfacial solvation dynamics of a model protein-surfactant interface. While C500 is found to be delocalized from the protein-surfactant interface, DCM becomes destabilized upon the formation of the interface (protein-surfactant complex). The timescales obtained from this novel probe have also been compared with other femtosecond resolved studies and molecular dynamics simulations.

  13. DNA-functionalized gold nanoparticle-based fluorescence polarization for the sensitive detection of silver ions.

    Science.gov (United States)

    Wang, Gongke; Wang, Shuangli; Yan, Changling; Bai, Guangyue; Liu, Yufang

    2018-04-05

    Despite their practical applications, Ag + ions are environmental pollutants and affect human health. So the effective detection methods of Ag + ions are imperative. Herein, we developed a simple, sensitive, selective, and cost-effective fluorescence polarization sensor for Ag + detection in aqueous solution using thiol-DNA-functionalized gold nanoparticles (AuNPs). In this sensing strategy, Ag + ions can specifically interact with a cytosine-cytosine (CC) mismatch in DNA duplexes and form stable metal-mediated cytosine-Ag + -cytosine (C-Ag + -C) base pairs. The formation of the C-Ag + -C complex results in evident changes in the molecular volume and fluorescence polarization signal. To achieve our aims, we prepared two complementary DNA strands containing C-base mismatches (probe A: 5'-SH-A 10 -TACCACTCCTCAC-3' and probe B: 5'-TCCTCACCAGTCCTA-FAM-3'). The stable hybridization between probe A and probe B occurs with the formation of the C-Ag + -C complex in the presence of Ag + ions, leading to obvious fluorescence quenching in comparison to the system without AuNP enhancement. The assay can be used to identify nanomolar levels of Ag + within 6 min at room temperature, and has extremely high specificity for Ag + , even in the presence of higher concentrations of interfering metal ions. Furthermore, the sensor was successfully applied to the detection of Ag + ions in environmental water samples and showed excellent selectivity and high sensitivity, implying its promising application in the future. Copyright © 2018 Elsevier B.V. All rights reserved.

  14. Communication: angular momentum alignment and fluorescence polarization of alkali atoms photodetached from helium nanodroplets.

    Science.gov (United States)

    Hernando, Alberto; Beswick, J Alberto; Halberstadt, Nadine

    2013-12-14

    The theory of photofragments angular momentum polarization is applied to the photodetachment of an electronically excited alkali atom from a helium nanocluster (N = 200). The alignment of the electronic angular momentum of the bare excited alkali atoms produced is calculated quantum mechanically by solving the excited states coupled equations with potentials determined by density functional theory (DFT). Pronounced oscillations as a function of excitation energy are predicted for the case of Na@(He)200, in marked contrast with the absorption cross-section and angular distribution of the ejected atoms which are smooth functions of the energy. These oscillations are due to quantum interference between different coherently excited photodetachment pathways. Experimentally, these oscillations should be reflected in the fluorescence polarization and polarization-resolved photoelectron yield of the ejected atoms, which are proportional to the electronic angular momentum alignment. In addition, this result is much more general than the test case of NaHe200 studied here. It should be observable for larger droplets, for higher excited electronic states, and for other alkali as well as for alkali-earth atoms. Detection of these oscillations would show that the widely used pseudo-diatomic model can be valid beyond the prediction of absorption spectra and could help in interpreting parts of the dynamics, as already hinted by some experimental results on angular anisotropy of bare alkali fragments.

  15. Potential applications of near infrared auto-fluorescence spectral polarized imaging for assessment of food quality

    Science.gov (United States)

    Zhou, Kenneth J.; Chen, Jun

    2016-03-01

    The current growing of food industry for low production costs and high efficiency needs for maintenance of high-quality standards and assurance of food safety while avoiding liability issues. Quality and safety of food depend on physical (texture, color, tenderness etc.), chemical (fat content, moisture, protein content, pH, etc.), and biological (total bacterial count etc.) features. There is a need for a rapid (less than a few minutes) and accurate detection system in order to optimize quality and assure safety of food. However, the fluorescence ranges for known fluorophores are limited to ultraviolet emission bands, which are not in the tissue near infrared (NIR) "optical window". Biological tissues excited by far-red or NIR light would exhibit strong emission in spectral range of 650-1,100 nm although no characteristic peaks show the emission from which known fluorophores. The characteristics of the auto-fluorescence emission of different types of tissues were found to be different between different tissue components such as fat, high quality muscle food. In this paper, NIR auto-fluorescence emission from different types of muscle food and fat was measured. The differences of fluorescence intensities of the different types of muscle food and fat emissions were observed. These can be explained by the change of the microscopic structure of physical, chemical, and biological features in meat. The difference of emission intensities of fat and lean meat tissues was applied to monitor food quality and safety using spectral polarized imaging, which can be detect deep depth fat under the muscle food up to several centimeter.

  16. OPTIMIZATION OF LAMBLIASIS MICROSCOPIC DIAGNOSTICS BY THE METHOD OF POLARIZED FLUORESCENCE FOR PATIENTS WITH ROSACEA AND URTICARIAL

    Directory of Open Access Journals (Sweden)

    Maryana Kovalchuk

    2013-07-01

    Full Text Available Introduction: There is little information about diagnosis of concurrent lambliasis in patients with rosacea and urticaria. We used method of polarized fluorescence to diagnose liambliasis, taking into account belonging of macromolecular structures of unicellular parasites Giardia lamblia to the optically active substances with the properties of liquid crystals. Material and Methods: Lambliasis was diagnosed on the basis of feces parasitological research and duodenal contents by methods of light and optic microscopy and polarized fluorescence in 105 patients with rosacea and urticaria. Research results were processed by the method of variation statistics in the Statgraf program by using Student’s criterion. Results: Search results of lamblia in patients with rosacea and urticaria depended on the conditions of its holding, patients’ preparation and from the previously received basic therapy if it consisted absorbents. Due to the fact that the fluorescence polarization as a physical method does not require the use of any generally toxic, dye- fluorochromes, qualitative cyto fluorescent analysis of lamblia in greeting microdrugs enables to distinguish vegetative forms of cysts. Conclussions: Polarized fluorescence method allows optimize the microscopic diagnosis of lambliasis, increasing its sensitivity. Previous preparation for the laboratory examination of Giardia lamblia is needed for the best exposure of vermin for patients with rosacea and urticaria.

  17. Fluorescence polarization assays to measure interactions between Gα subunits of heterotrimeric G proteins and regulatory motifs.

    Science.gov (United States)

    Maziarz, Marcin; Garcia-Marcos, Mikel

    2017-01-01

    Fluorescence polarization (FP) is a simple and sensitive method allowing for the quantification of interactions between proteins and fluorescently tagged small molecules like peptides. Heterotrimeric G proteins are critical signal transducing molecules and their activity is controlled by a complex network of regulatory proteins. Some of these regulators have defined short motifs (G proteins and subsequently modulate their activity. For these cases, FP represents a robust and quantitative method to characterize the G protein regulator interaction. Here we describe FP assays in a 384-well plate format to quantify interactions between Gα subunits of heterotrimeric G proteins and peptides corresponding to the Gα binding and activating (GBA) or GoLoco motifs, which are present in some proteins with guanine nucleotide exchange factor (GEF) (e.g., GIV/Girdin) or guanine nucleotide dissociation inhibitor (GDI) (e.g., RGS12) activity, respectively. This assay can be used to determine equilibrium dissociation constants, characterize the impact of single amino acid point mutations on the Gα-peptide interaction, and is suitable for high-throughput screening. © 2017 Elsevier Inc. All rights reserved.

  18. New method for preparing a liquid crystal polymer that exhibits linearly polarized white fluorescence

    International Nuclear Information System (INIS)

    Zheng Shijun; Kun, Wang; Kobayashi, Takaomi

    2011-01-01

    With the aim of developing a single-chain white-light-emitting polymer, liquid crystal (LC) polymers with a shish-kebab-type moiety on their cross-conjugated (p-phenylene)s-poly(p-phenylenevinylene)s main chain were synthesized by Gilch polymerization. They were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarizing optical microscopy (POM). 1 H-NMR indicated that the polymers had a shish-kebab structure, which strongly suppressed the formation of structural defects in the polymers. DSC revealed that the polymers had thermotropic LC properties, indicating that the LC polymers were enantiotropic. XRD showed that the polymers had a mesophase, which implies that they were in a smectic LC phase. A polymer with 'kebabs' of 2,5-bis(4'-alkoxyphenyl)benzene was combined with an aligned polyimide film with orientated microgrooves. The polymer main chain was aligned due to the orientation of the 'kebabs' of the uniform cross-conjugated structure. It lay between the kebabs and the 'shish' of the polymer main chains. The aligned polymer main chain emitted yellow light while and the oriented LC side chains emitted blue light emission. These two emissions resulted in linearly polarized white fluorescence.

  19. Removal of Chromophore-proximal Polar Atoms Decreases Water Content and Increases Fluorescence in a Near Infrared Phytofluor

    Directory of Open Access Journals (Sweden)

    Heli eLehtivuori

    2015-11-01

    Full Text Available Genetically encoded fluorescent markers have revolutionized cell and molecular biology due to their biological compatibility, controllable spatiotemporal expression, and photostability. To achieve in vivo imaging in whole animals, longer excitation wavelength probes are needed due to the superior ability of near infrared light to penetrate tissues unimpeded by absorbance from biomolecules or autofluorescence of water. Derived from near infrared-absorbing bacteriophytochromes, phytofluors are engineered to fluoresce in this region of the electromagnetic spectrum, although high quantum yield remains an elusive goal. An invariant aspartate residue is of utmost importance for photoconversion in native phytochromes, presumably due to the proximity of its backbone carbonyl to the pyrrole ring nitrogens of the biliverdin (BV chromophore as well as the size and charge of the side chain. We hypothesized that the polar interaction network formed by the charged side chain may contribute to the decay of the excited state via proton transfer. Thus, we chose to further probe the role of this amino acid by removing all possibility for polar interactions with its carboxylate side chain by incorporating leucine instead. The resultant fluorescent protein, WiPhy2, maintains BV binding, monomeric status, and long maximum excitation wavelength while minimizing undesirable protoporphyrin IXα binding in cells. A crystal structure and time-resolved fluorescence spectroscopy reveal that water near the BV chromophore is excluded and thus validate our hypothesis that removal of polar interactions leads to enhanced fluorescence by increasing the lifetime of the excited state. This new phytofluor maintains its fluorescent properties over a broad pH range and does not suffer from photobleaching. WiPhy2 achieves the best compromise to date between high fluorescence quantum yield and long illumination wavelength in this class of fluorescent proteins.

  20. A fluorescence polarization based screening assay for identification of small molecule inhibitors of the PICK1 PDZ domain

    DEFF Research Database (Denmark)

    Thorsen, Thor S; Madsen, Kenneth L; Dyhring, Tino

    2011-01-01

    PDZ (PSD-95/Discs-large/ZO-1 homology) domains represent putative targets in several diseases including cancer, stroke, addiction and neuropathic pain. Here we describe the application of a simple and fast screening assay based on fluorescence polarization (FP) to identify inhibitors of the PDZ...

  1. Rapid screening of aflatoxin B1 in beer by fluorescence polarization immunoassay.

    Science.gov (United States)

    Beloglazova, N V; Eremin, S A

    2015-09-01

    This manuscript describes the development of a sensitive, fast and easily-performed fluorescence polarization immunoassay (FPIA) for the mycotoxin aflatoxin B1 (AFB1) in various beer samples, both lager and dark. The highest sensitivity was determined for six poly- and monoclonal antibodies selective towards aflatoxins. The sample pretreatment design was emphasized since beer samples are characterized by extremely diverse matrices. Herein, the choice of sorbent for effective removal of matrix interferences prior to analysis was crucial. The samples were diluted with a borate buffer solution containing 1% PEG 6000 and passed through the clean-up column packed with NH2-derivated silica. This sample pretreatment technique was perfectly suitable for the FPIA of lager beer samples, but for dark beer and ale it did not suffice. An artificial matrix was constructed to plot a calibration curve and quantify the results of the latter samples. The developed immunoassay was characterized by a limit of detection of 1 ng mL(-1). Apparent recovery values of 89-114% for lager and 80-125% for dark beer were established. The FPIA data for AFB1 was characterized by elevated linear regression coefficients, 0.9953 for spiked lager and 0.9895 for dark beer samples respectively. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Tilting and Wobble of Myosin V by High-Speed Single-Molecule Polarized Fluorescence Microscopy

    Science.gov (United States)

    Beausang, John F.; Shroder, Deborah Y.; Nelson, Philip C.; Goldman, Yale E.

    2013-01-01

    Myosin V is biomolecular motor with two actin-binding domains (heads) that take multiple steps along actin by a hand-over-hand mechanism. We used high-speed polarized total internal reflection fluorescence (polTIRF) microscopy to study the structural dynamics of single myosin V molecules that had been labeled with bifunctional rhodamine linked to one of the calmodulins along the lever arm. With the use of time-correlated single-photon counting technology, the temporal resolution of the polTIRF microscope was improved ∼50-fold relative to earlier studies, and a maximum-likelihood, multitrace change-point algorithm was used to objectively determine the times when structural changes occurred. Short-lived substeps that displayed an abrupt increase in rotational mobility were detected during stepping, likely corresponding to random thermal fluctuations of the stepping head while it searched for its next actin-binding site. Thus, myosin V harnesses its fluctuating environment to extend its reach. Additional, less frequent angle changes, probably not directly associated with steps, were detected in both leading and trailing heads. The high-speed polTIRF method and change-point analysis may be applicable to single-molecule studies of other biological systems. PMID:23528086

  3. DART: Recent Advances in Remote Sensing Data Modeling With Atmosphere, Polarization, and Chlorophyll Fluorescence

    Science.gov (United States)

    Gastellu-Etchegorry, Jean-Phil; Lauret, Nicolas; Yin, Tiangang; Landier, Lucas; Kallel, Abdelaziz; Malenovsky, Zbynek; Bitar, Ahmad Al; Aval, Josselin; Benhmida, Sahar; Qi, Jianbo; hide

    2017-01-01

    To better understand the life-essential cycles and processes of our planet and to further develop remote sensing (RS) technology, there is an increasing need for models that simulate the radiative budget (RB) and RS acquisitions of urban and natural landscapes using physical approaches and considering the three-dimensional (3-D) architecture of Earth surfaces. Discrete anisotropic radiative transfer (DART) is one of the most comprehensive physically based 3-D models of Earth-atmosphere radiative transfer, covering the spectral domain from ultraviolet to thermal infrared wavelengths. It simulates the optical 3-DRB and optical signals of proximal, aerial, and satellite imaging spectrometers and laser scanners, for any urban and/or natural landscapes and for any experimental and instrumental configurations. It is freely available for research and teaching activities. In this paper, we briefly introduce DART theory and present recent advances in simulated sensors (LiDAR and cameras with finite field of view) and modeling mechanisms (atmosphere, specular reflectance with polarization and chlorophyll fluorescence). A case study demonstrating a novel application of DART to investigate urban landscapes is also presented.

  4. A compact fluorescence polarization analyzer with high-transmittance liquid crystal layer

    Science.gov (United States)

    Wakao, Osamu; Satou, Ken; Nakamura, Ayano; Sumiyoshi, Ken; Shirokawa, Masanori; Mizokuchi, Chikaaki; Shiota, Kunihiro; Maeki, Masatoshi; Ishida, Akihiko; Tani, Hirofumi; Shigemura, Koji; Hibara, Akihide; Tokeshi, Manabu

    2018-02-01

    Fluorescence polarization (FP) offers easy operation and rapid processing, making it implementable in molecular interaction analysis. Previously we have developed a unique FP measurement system using a liquid crystal (LC) layer and an image sensor. The system is based on a principle of synchronized detection between the switching rate of the LC layer and the sampling rate of the CCD. The FP system realized simultaneous multiple sample detection; however, the measurement precision was lower than that of the conventional FP apparatus. The main drawbacks were low light transmittance of the LC layer and insufficient synchronization between the LC layer and CCD. In this paper, we developed a new FP analyzer based on LC-CCD synchronization detection. By using a newly designed LC with high transmittance and improving synchronization, the performance of the system has been dramatically improved. Additionally, we reduced the cost by using an inexpensive CCD and an LED as the excitation source. Simultaneous FP immunoassay of multiple samples of prostaglandin E2 was performed. The error rate of the FP system is reduced from 16.9% to 3.9%, as comparable to the commercial conventional FP system.

  5. Simultaneous detection of four common oral Candida species from blood samples by the fluorescence polarization assay.

    Science.gov (United States)

    He, Yuhong; Geng, Wei; Wang, Peihuan; Xi, Lanlan; Wang, Zhaoling; Wu, Gaoyi; Wang, Chunling

    2015-03-01

    The genus Candida is both the commensal microbe and the opportunistic pathogen, containing approximately 200 species inhabiting in oral cavity of 53 % of the general population. Candida species can cause the diseases from local mucosal infections to systemic mycoses, even life-threatening infections in immunocompromised individuals. The timely differentiation of Candida species is important for the guidance of clinical medication. Four common Candida species in Chinese population (Candida albicans, Candida tropicalis, Candida glabrata, Candida krusei) were chosen as the targets to develop the rapid screening method in this work. Combined with amplification by asymmetric PCR, this parallel fluorescence polarization (FP) immunoassay is carried out in homogeneous solution phase. The limit of detection of the assay was shown to be 50 copies/mL in blood samples. The evaluation in multicenter manner showed excellent reproducibility and stability. The comparison between DNA sequencing and the FP immunoassay indicated that there was no significant difference between these methods. This molecular strategy-based method is simple, rapid, and feasible for identifying common Candida species and thereby holding great potential in the application of clinical laboratories.

  6. Heterologous strategy enhancing the sensitivity of the fluorescence polarization immunoassay of clinafloxacin in goat milk.

    Science.gov (United States)

    Chen, Jiahong; Shanin, Ilya A; Lv, Shuwei; Wang, Qiang; Mao, Chuanbin; Xu, Zhenlin; Sun, Yuanming; Wu, Qing; Eremin, Sergei A; Lei, Hongtao

    2016-03-15

    Clinafloxacin is used for the treatment of disease in food-producing animals, e.g. Brucella melitensis, which often occurs in goats; however, the clinafloxacin residue in goat milk may harm human health and result in the development of drug-resistant bacterial strains or allergies. Despite this, there is not a rapid, sensitive and accurate analytical method in goat milk for rapid screening or monitoring purposes. One homologous and five heterologous tracers were designed and compared for fluorescence polarization immunoassay (FPIA) optimization. Based on the combination of a heterologous tracer (PAZ-FITC, synthesized with pazufloxacin and FITC) and the antibody against clinafloxacin, a highly sensitive FPIA was established for the detection of clinafloxacin residue in goat milk for the first time. The IC50 value was 29.3 µg L(-1) for clinafloxacin in the heterologous format - six times lower than that of the combination of the homologous tracers and the antibody. The recoveries ranged from 86.8% to 104.5%, with the relative standard deviation ranging from 4.1% to 7.2%. Validation by high-performance liquid chromatography (HPLC) confirmed that the results obtained from the proposed FPIA were in agreement with those of HPLC. This proposed heterologous strategy for enhanced FPIA is sensitive and rapid enough for the high-throughput detection of clinafloxacin residue in goat milk. © 2015 Society of Chemical Industry.

  7. Characterization and optimization of a red-shifted fluorescence polarization ADP detection assay.

    Science.gov (United States)

    Kleman-Leyer, Karen M; Klink, Tony A; Kopp, Andrew L; Westermeyer, Thane A; Koeff, Mark D; Larson, Brad R; Worzella, Tracy J; Pinchard, Cori A; van de Kar, Sebastianus A T; Zaman, Guido J R; Hornberg, Jorrit J; Lowery, Robert G

    2009-02-01

    ATP depletion and ADP formation are generic detection methods used for the identification of kinase and other ATP-utilizing enzyme inhibitors in high-throughput screening campaigns. However, the most widely used nucleotide detection approaches require high ATP consumption rates or involve the use of coupling enzymes, which can complicate the selection of lead compounds. As an alternative, we have developed the Transcreener (BellBrook Labs, Madison, WI) platform, which relies on the direct immunodetection of nucleotides. Here we describe the development of antibodies with >100-fold selectivity for ADP versus ATP, which enable robust detection of initial velocity rates (Z' > 0.7 at 10% substrate consumption) at ATP concentrations ranging from 0.1 microM to 1,000 microM in a competitive fluorescence polarization (FP) immunoassay. Competitive binding experiments indicate similar affinities for other nucleotide diphosphates, including 2' -deoxy ADP, GDP, and UDP. The antibody-tracer complex and the red-shifted, ratiometric FP signal are stable for at least 24 h at room temperature, providing suitable conditions for high-throughput screening. A method for calculating a kinase ATP Km with this FP immunoassay is also presented. The Transcreener ADP assay provides a simple, generic assay platform for inhibitor screening and selectivity profiling that can be used for any ADP-generating enzyme.

  8. Development of an in situ polarization-dependent total-reflection fluorescence XAFS measurement system.

    Science.gov (United States)

    Chun, W J; Tanizawa, Y; Shido, T; Iwasawa, Y; Nomura, M; Asakura, K

    2001-03-01

    An in situ polarization-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) spectroscopy system has been developed, which enables PTRF-XAFS experiments to be performed in three different orientations at various temperatures (273-600 K) and pressures (10(-10) approximately 760 torr). The system consists of a measurement chamber and a preparation chamber. The measurement chamber has a high-precision six-axis goniometer and a multielement solid-state detector. Using a transfer chamber, also operated under ultra-high-vacuum conditions, the sample can be transferred to the measurement chamber from the preparation chamber, which possesses low-energy electron diffraction, Auger electron spectroscopy and X-ray photoelectron spectroscopy facilities, as well as a sputtering gun and an annealing system. The in situ PTRF-EXAFS for Cu species on TiO2 (110) has been measured in three different orientations, revealing anisotropic growth of Cu under the influence of the TiO2 (110) surface.

  9. Multi-element analysis of pyrite ores using polarized energy-dispersive X-ray fluorescence spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Ustuendag, Zafer [Department of Chemistry, Faculty of Science, Ankara University, Ankara (Turkey)]. E-mail: zustun@science.ankara.edu.tr; Ustuendag, Ilknur [Department of Physics Engineering, Faculty of Engineering, Hacettepe University, Ankara (Turkey); Kagan Kadioglu, Yusuf [Department of Geological Engineering, Faculty of Engineering, Ankara University, Ankara (Turkey)

    2007-07-15

    X-ray fluorescence (XRF) spectrometry is used worldwide in geological material analysis. This study, applies polarized energy-dispersive X-ray fluorescence (PEDXRF) Spectrometer and compares in the samples of Rize-Cayeli and Mardin pyrite ores. The samples of pyrite ore were collected from the Rize and Mardin in Turkey. The prepared samples were analyzed using a PEDXRF spectrometer. The result of the analysis shows the presence of many elements including rare-earth elements (from Na to Th). The accuracy and precision of the technique for chemical analysis is demonstrated by analyzing USGS standards, GEOL, GBW 7109 and GBW-7309 sediment.

  10. Polarity-Tunable Host Materials and Their Applications in Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes.

    Science.gov (United States)

    Xie, Gaozhan; Chen, Dongjun; Li, Xianglong; Cai, Xinyi; Li, Yunchuan; Chen, Dongcheng; Liu, Kunkun; Zhang, Qian; Cao, Yong; Su, Shi-Jian

    2016-10-04

    A series of polarity-tunable host materials were developed based on oligocarbazoles and diphenylphosphine oxide, and their polarities can be tuned through increasing distance of acceptor and donor units. Density functional theory calculations were employed, and photoluminescence spectra in different polar solvents were measured to illustrate different polarities of these host materials. As CZPO has relatively stronger polarity, electroluminescence (EL) spectrum of solution-processed device based on 6 wt % PXZDSO2:CZPO is 7 nm red-shifted relative to that of other host materials based devices. Besides, a comparable impressive external quantum efficiency (EQE) value of 18.7% is achieved for an evaporation-processed yellow device consisting of FCZBn, which is superior to that of the device based on CBP (4,4'-dicarbazolyl-1,1'-biphenyl) (17.0%), and its efficiency roll-off is also obviously reduced, giving an EQE value as high as 16.3% at the luminance of 1000 cd/m 2 . In addition, from CZPO to FCZBn as the polarities of host materials decrease, EL spectra of solution-processed devices based on DMAC-DPS emitter blue-shift constantly from 496 to 470 nm. The current work gives a constructive approach to control EL spectra of organic light-emitting diodes with a fixed thermally activated delayed fluorescence emitter by tuning the polarities of host materials.

  11. Development of a High-Throughput Fluorescence Polarization Assay to Identify Novel Ligands of Glutamate Carboxypeptidase II

    Czech Academy of Sciences Publication Activity Database

    Alquicer, Glenda; Sedlák, David; Byun, Y.; Pavlíček, Jiří; Stathis, M.; Rojas, C.; Slusher, B.; Pomper, M.G.; Bartůněk, Petr; Bařinka, Cyril

    2012-01-01

    Roč. 17, č. 8 (2012), s. 1030-1040 ISSN 1087-0571 R&D Projects: GA MŠk(CZ) ME10031; GA MŠk(CZ) LC06077 Institutional research plan: CEZ:AV0Z50520701 Institutional support: RVO:68378050 Keywords : fluorescence polarization * glutamate carboxypeptidase II * high-throughput screening Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.207, year: 2012

  12. Carbon nanotube signal amplification for ultrasensitive fluorescence polarization detection of DNA methyltransferase activity and inhibition.

    Science.gov (United States)

    Huang, Yong; Shi, Ming; Zhao, Limin; Zhao, Shulin; Hu, Kun; Chen, Zheng-Feng; Chen, Jia; Liang, Hong

    2014-04-15

    A versatile sensing platform based on multiwalled carbon nanotube (MWCNT) signal amplification and fluorescence polarization (FP) is developed for the simple and ultrasensitive monitoring of DNA methyltransferase (MTase) activity and inhibition in homogeneous solution. This method uses a dye-labeled DNA probe that possess a doubled-stranded DNA (dsDNA) part for Mtase and its corresponding restriction endonuclease recognition, and a single-stranded DNA part for binding MWCNTs. In the absence of MTase, the dye-labeled DNA is cleaved by restriction endonuclease, and releases very short DNA carrying the dye that cannot bind to MWCNTs, which has relatively small FP value. However, in the presence of MTase, the specific recognition sequence in the dye-labeled DNA probe is methylated and not cleaved by restriction endonuclease. Thus, the dye-labeled methylated DNA product is adsorbed onto MWCNTs via strong π-π stacking interactions, which leads to a significant increase in the FP value due to the enlargement of the molecular volume of the dye-labeled methylated DNA/MWCNTs complex. This provides the basic of a quantitative measurement of MTase activity. By using the MWCNT signal amplification approach, the detection sensitivity can be significantly improved by two orders of magnitude over the previously reported methods. Moreover, this method also has high specificity and a wide dynamic range of over five orders of magnitude. Additionally, the suitability of this sensing platform for MTase inhibitor screening has also been demonstrated. This approach may serve as a general detection platform for sensitive assay of a variety of DNA MTases and screening potential drugs. © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

  13. Investigation of the Stability of the Ruthenium based Dye (N719) Utilizing the Polarization Properties of Dispersive Raman Modes and/or of the Fluorescent Emission

    DEFF Research Database (Denmark)

    Hassing, Søren; Jernshøj, Kit Drescher; Phuong, Nguyen

    2013-01-01

    for short) is possible by exploiting a combination of the polarization properties of the dispersive Raman modes with the small spectral change in the visible absorption spectrum and/or the difference in the polarization of the fluorescence related to the difference in molecular configuration. By measuring...

  14. Fluorescence of the gamma, epsilon, and delta systems of nitric oxide - Polarization and use of calculated intensities for spectrometer calibration.

    Science.gov (United States)

    Poland, H. M.; Broida, H. P.

    1971-01-01

    Results of a study in which fluorescence of the gamma system of nitric oxide was obtained by excitation from both the 2144 A line of ionized cadmium and a continuum source. Individual rotational lines of the 2144 A excited fluorescence spectrum were found to be partially polarized and to have polarizations of differ ing sign. Measured relative vibrational band intensities from line and continuum excitation were compared to calculated Franck-Condon factors. Those Franck-Condon factors based on a single potential for the two spin states of the X super pi state agreed better with measured values than those based on separate potentials for the two spin states. Calculated intensities of the v prime = 3 progression were used to calibrate the instrument response in the wavelength region from 2000 to 2500 A and were checked with measured intensities of the v prime = 0.1, and 2 progressions. Fluorescence of the epsilon and delta bands obtained with continuum lamp excitation also were compared to calculated intensities.

  15. Ultrafast polarized fluorescence measurements on monomeric and self-associated melittin

    NARCIS (Netherlands)

    Pandit, A.; Larsen, O.F.A.; Stokkum, van I.H.M.; Grondelle, van R.; Kraayenhof, R.; Amerongen, van H.

    2003-01-01

    The anisotropic and magic-angle fluorescence decay of the single tryptophan (Trp) residue of melittin, a bee venom peptide, was investigated by time-resolved fluorescence anisotropy using a streak camera setup. The peptide was dissolved either in distilled water or in Hepes/NaOH buffer containing

  16. Fluorescence emission and polarization analyses for evaluating binding of ruthenium metalloglycocluster to lectin and tetanus toxin c-fragment

    Science.gov (United States)

    Okada, Tomoko; Minoura, Norihiko

    2010-02-01

    We have developed a fluorescent ruthenium metalloglycocluster as a powerful molecular probe for evaluating a binding event between carbohydrates and lectins by fluorescence emission (FE) and fluorescence polarization (FP) analysis. The fluorescent ruthenium metalloglycoclusters, [Ru(bpy-2Gal)3] and [Ru(bpy-2Glc)3], possess clustered galactose and glucose surrounding the ruthenium center. Changes in FE and FP of these metalloglycoclusters were measured by adding each lectin (Peanut agglutinin (PNA), Ricinus communis agglutinin 120 (RCA), Concanavalin A (ConA), or Wheat germ agglutinin (WGA)) or tetanus toxin c-fragment (TCF). Following the addition of PNA, the FE spectrum of [Ru(bpy- 2Gal)3] showed new emission peak and the FP value of [Ru(bpy-2Gal)3] increased. Similarly, the FE spectrum of [Ru(bpy-2Glc)3] showed new emission peak and the FP value increased following the addition of ConA. Since other combinations of the metalloglycoclusters and lectin caused little change, specific bindings of galactose to PNA and glucose to ConA were proved by the FE and FP measurement. From nonlinear least-squares fitting, dissociation constants (Kd) of [Ru(bpy-2Gal)3] to PNA was 6.1 μM, while the Kd values of [Ru(bpy)2(bpy-2Gal)] to PNA was ca. 10-4 M. Therefore, the clustered carbohydrates were proved to increase affinity to lectins. Furthermore, the FP measurements proved specific binding of [Ru(bpy-2Gal)3] to TCF.

  17. HPLC-fluorescence detection method for determination of key intermediates of the lincomycin biosynthesis in fermentation broth

    Czech Academy of Sciences Publication Activity Database

    Kameník, Zdeněk; Kopecký, J.; Marečková, M.; Ulanová, Dana; Novotná, Jitka; Pospíšil, Stanislav; Olšovská, Jana

    2009-01-01

    Roč. 393, 6-7 (2009), s. 1779-1787 ISSN 1618-2642 R&D Projects: GA ČR GA204/05/0616; GA AV ČR IAA6020410; GA MŠk 2B08064 Institutional research plan: CEZ:AV0Z50200510 Keywords : Lincomycin precursors * o-Phthaldialdehyde * Fluorescence detection Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.480, year: 2009

  18. Quantitative light fluorescence (QLF) and polarized white light (PWL) assessments of dental fluorosis in an epidemiological setting.

    Science.gov (United States)

    Pretty, Iain A; McGrady, Michael; Zakian, Christian; Ellwood, Roger P; Taylor, Andrew; Sharif, Mohammed Owaise; Iafolla, Timothy; Martinez-Mier, E Angeles; Srisilapanan, Patcharawan; Korwanich, Narumanas; Goodwin, Michaela; Dye, Bruce A

    2012-05-20

    To determine if a novel dual camera imaging system employing both polarized white light (PWL) and quantitative light induced fluorescence imaging (QLF) is appropriate for measuring enamel fluorosis in an epidemiological setting. The use of remote and objective scoring systems is of importance in fluorosis assessments due to the potential risk of examiner bias using clinical methods. Subjects were recruited from a panel previously characterized for fluorosis and caries to ensure a range of fluorosis presentation. A total of 164 children, aged 11 years (±1.3) participated following consent. Each child was examined using the novel imaging system, a traditional digital SLR camera, and clinically using the Dean's and Thylstrup and Fejerskov (TF) Indices on the upper central and lateral incisors. Polarized white light and SLR images were scored for both Dean's and TF indices by raters and fluorescence images were automatically scored using software. Data from 164 children were available with a good distribution of fluorosis severity. The automated software analysis of QLF images demonstrated significant correlations with the clinical examinations for both Dean's and TF index. Agreement (measured by weighted Kappa's) between examiners scoring clinically, from polarized photographs and from SLR images ranged from 0.56 to 0.92. The study suggests that the use of a digital imaging system to capture images for either automated software analysis, or remote assessment by raters is suitable for epidemiological work. The use of recorded images enables study archiving, assessment by multiple examiners, remote assessment and objectivity due to the blinding of subject status.

  19. Quantitative Light Fluorescence (QLF and Polarized White Light (PWL assessments of dental fluorosis in an epidemiological setting

    Directory of Open Access Journals (Sweden)

    Pretty Iain A

    2012-05-01

    Full Text Available Abstract Background To determine if a novel dual camera imaging system employing both polarized white light (PWL and quantitative light induced fluorescence imaging (QLF is appropriate for measuring enamel fluorosis in an epidemiological setting. The use of remote and objective scoring systems is of importance in fluorosis assessments due to the potential risk of examiner bias using clinical methods. Methods Subjects were recruited from a panel previously characterized for fluorosis and caries to ensure a range of fluorosis presentation. A total of 164 children, aged 11 years (±1.3 participated following consent. Each child was examined using the novel imaging system, a traditional digital SLR camera, and clinically using the Dean’s and Thylstrup and Fejerskov (TF Indices on the upper central and lateral incisors. Polarized white light and SLR images were scored for both Dean’s and TF indices by raters and fluorescence images were automatically scored using software. Results Data from 164 children were available with a good distribution of fluorosis severity. The automated software analysis of QLF images demonstrated significant correlations with the clinical examinations for both Dean’s and TF index. Agreement (measured by weighted Kappa’s between examiners scoring clinically, from polarized photographs and from SLR images ranged from 0.56 to 0.92. Conclusions The study suggests that the use of a digital imaging system to capture images for either automated software analysis, or remote assessment by raters is suitable for epidemiological work. The use of recorded images enables study archiving, assessment by multiple examiners, remote assessment and objectivity due to the blinding of subject status.

  20. Fluorescence emission and polarization analyses for evaluating binding of ruthenium metalloglycoclusters to lectins and tetanus toxin C-fragment

    Science.gov (United States)

    Okada, Tomoko; Minoura, Norihiko

    2011-03-01

    We develop a fluorescent ruthenium metalloglycocluster for use as a powerful molecular probe in evaluating the binding between carbohydrates and lectins by fluorescence emission (FE) and fluorescence polarization (FP) analyses. Changes in the FE and FP of these metalloglycoclusters are measured following the addition of lectin [peanut agglutinin (PNA), Ricinus communis agglutinin 120, Concanavalin A (ConA), or wheat germ agglutinin] or tetanus toxin c-fragment (TCF). After the addition of PNA, the FE spectrum of [Ru(bpy-2Gal)3] shows a new emission peak and the FP value of [Ru(bpy-2Gal)3] increases. Similarly, the FE spectrum of [Ru(bpy-2Glc)3] shows a new emission peak and the FP value increases on addition of ConA. Because other combinations of metalloglycoclusters and lectins show little change, specific binding of galactose to PNA and that of glucose to ConA are confirmed by the FE and FP measurements. Resulting dissociation constants (Kd) prove that the metalloglycoclusters with highly clustered carbohydrates show higher affinity for the respective lectins than those with less clustered carbohydrates. Furthermore, specific binding of [Ru(bpy-2Gal)3] to TCF was confirmed by the FP measurement.

  1. Determination of heavy metals in polar snow and ice by laser-excited atomic fluorescence spectrometry

    International Nuclear Information System (INIS)

    Bolshov, M.A.; Boutron, C.F.

    1994-01-01

    The new laser-excited atomic fluorescence spectrometry technique offers unrivalled sensitivity for the determination of trace metals in a wide variety of samples. This has allowed the direct determination of Pb, Cd and Bi in Antarctic and Greenland snow and ice down to the sub pg/g level. (authors). 11 refs., 2 figs

  2. Fluorescence study of arene probe microenvironment in the intraparticle void volume of zeolites interfaced with bathing polar solvents.

    Science.gov (United States)

    Ellison, Eric H; Moodley, Deshi; Hime, Joseph

    2006-03-16

    Fluorescence methodologies have been utilized to examine micropolarity, intramolecular motion, and singlet quenching in the intraparticle void volume of zeolites X, Y, and ultrastable Y (USY) interfaced with bathing polar solvents. Micropolarity was assessed from the 3-to-1 band ratio (III/I) of the fluorescence spectrum of pyrene (PY) and from lambda(max) of the fluorescence spectrum of 1-pyrenecarboxaldehyde (1-PCA). In zeolites bathed in anhydrous solvents, both PY and 1-PCA reported increased micropolarity according to the trend USY nitrocompounds dissolved in solvents bathing the zeolite was examined by a time-resolved approach. For all of the quenchers and solvents studied, quenching was more efficient in USY compared to NaX and NaY. Interestingly, the rate of O2 quenching in USY-MeOH was only 12 times lower than that in bulk MeOH. In contrast, in NaY-MeOH and NaX-MeOH the rate of O2 quenching was too low to be measured. The rate constants in these systems were therefore taken as the rate constant for diffusion-controlled quenching of trapped electrons measured previously. These values were 600 times and 10(5) times lower than the rate of fluorescence quenching in USY-MeOH, respectively. The O2 quenching studies show that dispersive interactions of polar solvents with the cavity walls dominate in USY because of the hydrophobic nature of the USY surface. In NaX and NaY, stronger ion-dipole and hydrogen bonding interactions dominate and lead to more restricted access and lowered quenching efficiency. Perrin (or static) quenching of pyrene fluorescence was also examined to infer the concentration of nitromethane (NM) in the void volume of NaX and NaY bathed in MeOH, ACN, or H2O. The results indicate that access of NM to the interior of NaY is more inhibited in ACN compared to MeOH, presumably because of the higher dipole moment of ACN and its resulting stronger association with the zeolite surface. At similar levels of static quenching equated to a similar NM

  3. Fish polar lipids retard atherosclerosis in rabbits by down-regulating PAF biosynthesis and up-regulating PAF catabolism.

    Science.gov (United States)

    Nasopoulou, Constantina; Tsoupras, Alexandros B; Karantonis, Haralabos C; Demopoulos, Constantinos A; Zabetakis, Ioannis

    2011-11-16

    Platelet activating factor (PAF) has been proposed as a key factor and initial trigger in atherosclerosis. Recently, a modulation of PAF metabolism by bioactive food constituents has been suggested. In this study we investigated the effect of fish polar lipid consumption on PAF metabolism. The specific activities of four PAF metabolic enzymes; in leukocytes, platelets and plasma, and PAF concentration; either in blood cells or plasma were determined. Samples were acquired at the beginning and at the end of a previously conducted study in male New Zealand white rabbits that were fed for 45 days with atherogenic diet supplemented (group-B, n = 6) or not (group-A, n = 6) with gilthead sea bream (Sparus aurata) polar lipids.The specific activity of PAF-Acetylhydrolase (PAF-AH); a catabolic enzyme of PAF, was decreased in rabbits' platelets of both A and B groups and in rabbits' leukocytes of group A (p PAF in plasma was increased in both A and B groups in both leukocytes and platelets (p PAF-cholinephosphotransferase (PAF-CPT); a biosynthetic enzyme of PAF showed increased specific activity only in rabbits' leukocytes of group A (p PAF-acetyltransferase (Lyso-PAF-AT) specific activity (p > 0.05). Free and bound PAF levels increased in group A while decreased in group B (p PAF metabolism upon atherosclerotic conditions in rabbits leading to lower PAF levels and activity in blood of rabbits with reduced early atherosclerotic lesions compared to control group.

  4. Automated system to acquire fluorescence, polarization and anisotropy maps within liquid flows.

    Science.gov (United States)

    Quintella, Cristina M; Gonçalves, Cristiane C; Pepe, Iuri; Lima, Angelo M V; Musse, Ana Paula S

    2002-01-01

    Maps of polarization and anisotropy can be helpful for flow analysis systems (FIA, CFA, etc.) with reactions dependent on the intermolecular alignment as well as for dispersion control. Maps can be acquired manually, but when a scan over a sample area is required, the acquisition becomes tiresome and has low precision. The paper describes an automatic flexible system for high-precision sample positioning with closed loop self control, remote data acquisition and storage controlled by a BASIC program. The system was developed to acquire maps up to 850 mm(2) of the sample (liquid flows, solids, interfaces, etc.), with up to 100 mum(2) precision. To evaluate the equipment, performance is presented as the scan of a thin liquid film of monoethylene glycol (MEG) flowing on borosilicate. Tests were performed with and without surfactantes at submicellar concentrations: two concentrations of sodium dodecyl sulphate (SDS) and one of polyethylene oxide (PEO). For pure MEG, the intermolecular alignment initially increased, then decreased. When SDS was added, both polarization and anisotropy only increased progressively with the flow. This might be explained by the surfactant decrease of interfacial interaction. When PEO was added, both polarization and anisotropy decreased pronouncedly over the entire map, which might be due to macromolecular aggregates within the bulk generating misaligned molecular domains. The system presented as sample positioning repeatability of 0.1% and a high polarization reproducibility (error margin < 6 in 1000).

  5. Polarized fluorescence measurements of orientational order in a uniaxial liquid crystal

    DEFF Research Database (Denmark)

    Chapoy, L. Lawrence; DuPré, Donald B.

    1979-01-01

    The second and fourth orientational order parameters and , have been measured throughout the liquid crystalline phase of p-methoxybenzylidene-p[prime]-n-butylaniline (MBBA) using small quantities of a fluorescent probe. Complications of rotational Brownian motion and the intramolecular transfer o...... of excitation energy were considered in the analysis. The results are in agreement with previous Raman measurements on the doped liquid crystal. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.......The second and fourth orientational order parameters and , have been measured throughout the liquid crystalline phase of p-methoxybenzylidene-p[prime]-n-butylaniline (MBBA) using small quantities of a fluorescent probe. Complications of rotational Brownian motion and the intramolecular transfer...

  6. Evaluation of a fluorescent polarization immunoassay for whole blood everolimus determination using samples from renal transplant recipients.

    Science.gov (United States)

    Salm, Paul; Warnholtz, Christopher; Boyd, Jared; Arabshahi, Lili; Marbach, Peter; Taylor, Paul J

    2006-07-01

    This study compared the performance of a fluorescent polarization immunoassay (FPIA) against HPLC-tandem mass spectrometry (HPLC-MS) for the measurement of everolimus in renal transplant recipients. A total of 333 pre-dose samples from 45 renal transplant patients were analyzed by FPIA and HPLC-MS. The inter-batch inaccuracy and precision of the FPIA for control samples were equation FPIA = 1.19 x HPLC-MS + 0.51. The mean bias was 24.4% (95% CI: -3.0 to 54.2%, range: -30.1% to 79.4%). The FPIA had acceptable analytical performance during the study but compared to HPLC-MS overestimated everolimus in patient samples. This overestimation is probably due to calibration differences between the methods and cross-reactivity of the FPIA antibody with everolimus metabolites. The clinical importance of the observed overestimation by FPIA requires further investigation.

  7. Comparison of capillary electrophoresis-based immunoassay with fluorescence polarization immunoassay for the immunodetermination of methamphetamine using various methamphetamine antibodies.

    Science.gov (United States)

    Choi, J; Kim, C; Choi, M J

    1998-11-01

    An accurate and simple immunoassay using capillary electrophoresis (CE) with laser-induced fluorescence (LIF) was performed for the detection of methamphetamine (MA) in urine. The CE-LIF was conducted with an untreated fused-silica column using antiserum and a tracer of fluorescein isothiocyanate (FITC)-labeled MA. This CE-LIF system was compared with fluorescence polarization immunoassay (FPIA) in a TDx analyzer in the photo-check mode using the same FITC-labeled tracer and the same antiserum. Various antibodies, not only those prepared by our own immunogens but also those from commercial sources, were screened and characterized in both assay systems with regard to sensitivity, precision, and cross-reactivity. Both systems satisfied analytical precision and gave similar cross-reactivity patterns. However, the CE-LIF-based immunoassay was approximately one order superior to FPIA in sensitivity, requiring less volume of sample, antiserum, and tracer for the assay. Considering that the FPIA system is well known to be a useful tool for screening antibodies and detecting drugs, the CE-LIF-based immunoassay system, which is seemingly more advantageous than the FPIA system, appears to have great power for the characterization of antibodies and for the detection of MA in urine.

  8. Growth, polarized Raman and fluorescence properties of TbCa4O(BO3)3 single crystal

    Science.gov (United States)

    Yuan, Dongsheng; Gao, Zeliang; Jia, Zhitai; Shu, Jun; Li, Yang; Tao, Xutang

    2015-04-01

    A single crystal of TbCa4O(BO3)3 (TbCOB) with diameter of 35 mm and length of 80 mm has been successfully grown using the Czochralski (Cz) method. The polarized Raman spectra were studied to analyze the vibrational structure of TbCOB, especially the modes from [BO3]3- triangles that are responsible for the nonlinear optical generation. The fluorescence properties of the X-cut, Y-cut, and Z-cut non-centrosymmetric TbCOB crystals were measured for the first time, and both f-d and f-f transitions were identified according to the energy level diagram. Based on the non-radiative energy transfer process, TbCOB crystal shows the characteristic emission of Tb3+ corresponding to 5D4 → 7F6,5,4,3 transitions with the green light of 542 nm (5D4 → 7F5) being the most prominent group. Additionally, the lifetime decay indicates single exponential character for the excited wavelength at 378 nm, following the result of τ = 2.07 ms at room temperature. The long fluorescence lifetime and good spectra properties of TbCOB single crystal indicate its potential optical prospects.

  9. Enzymatic studies on planar supported membranes using a widefield fluorescence LAURDAN Generalized Polarization imaging approach

    DEFF Research Database (Denmark)

    Brewer, Jonathan R.; Thoke, Henrik Seir; Stock, Robeto

    2017-01-01

    the temporal resolution previously achieved using laser scanning based microscopes. A dedicated protocol to calibrate LAURDAN GP data obtained with charge-coupled device (CCD) cameras as detectors is also presented, enabling reliable assignment of GP values in the field of view. Using this methodology we...... to a single solid ordered phase at longer time scales. Additionally, we comparatively studied this system using the membrane fluorophore DiIC18. The advantages and limitations of both fluorescent dyes are discussed, emphasizing the adequacy of LAURDAN GP imaging to explore this type of membrane phenomena....

  10. Plane polarized x-ray fluorescence system for the in vivo measurement of platinum in head and neck tumours

    Science.gov (United States)

    Ali, P. A.; Al-Hussany, A. F.; Bennett, C. A.; Hancock, D. A.; El-Sharkawi, A. M.

    1998-08-01

    A plane polarized x-ray fluorescence system based on an orthovoltage radiotherapy treatment unit, the Pantak DXT-300, has been developed and optimized to measure tumour platinum concentration. The platinum derives from platinum based chemotherapy agents, such as cisplatin and carboplatin used to treat tumours in the head and neck region. Photons from an x-ray tube are polarized by scattering through , and used to stimulate the emission of characteristic platinum x-rays from the tumour. Information about the drug in the tumour could be of use in establishing dose-response relationships, in order to optimize the treatment and reduce the toxicity of the drug. The performance of the system was optimized with respect to the applied x-ray tube voltage, the current and the filter material; the effect on the minimum detection limit (MDL) of the thickness of the overlying tissue surrounding the tumour was investigated in detail. The lowest MDL is achieved using 0.25 mm of tin filter and x-ray tube voltage of 220 kV. This is 5.6 ppm for a tumour surrounded with 20 mm of overlying tissue, a measurement time of 2000 s and an estimated skin dose of 3.0 mGy. This represents the most sensitive in vivo XRF system to date. We have embarked on a clinical pilot study to measure the platinum concentration in tumours of the head and neck, and expect initial results to be available in the near future.

  11. Single-molecule fluorescence polarization study of conformational change in archaeal group II chaperonin.

    Directory of Open Access Journals (Sweden)

    Ryo Iizuka

    Full Text Available Group II chaperonins found in archaea and in eukaryotic cytosol mediate protein folding without a GroES-like cofactor. The function of the cofactor is substituted by the helical protrusion at the tip of the apical domain, which forms a built-in lid on the central cavity. Although many studies on the change in lid conformation coupled to the binding and hydrolysis of nucleotides have been conducted, the molecular mechanism of lid closure remains poorly understood. Here, we performed a single-molecule polarization modulation to probe the rotation of the helical protrusion of a chaperonin from a hyperthermophilic archaeum, Thermococcus sp. strain KS-1. We detected approximately 35° rotation of the helical protrusion immediately after photorelease of ATP. The result suggests that the conformational change from the open lid to the closed lid state is responsible for the approximately 35° rotation of the helical protrusion.

  12. Attomolar detection of proteins via cascade strand-displacement amplification and polystyrene nanoparticle enhancement in fluorescence polarization aptasensors.

    Science.gov (United States)

    Huang, Yong; Liu, Xiaoqian; Huang, Huakui; Qin, Jian; Zhang, Liangliang; Zhao, Shulin; Chen, Zhen-Feng; Liang, Hong

    2015-08-18

    Extremely sensitive and accurate measurements of protein markers for early detection and monitoring of diseases pose a formidable challenge. Herein, we develop a new type of amplified fluorescence polarization (FP) aptasensor based on allostery-triggered cascade strand-displacement amplification (CSDA) and polystyrene nanoparticle (PS NP) enhancement for ultrasensitive detection of proteins. The assay system consists of a fluorescent dye-labeled aptamer hairpin probe and a PS NP-modified DNA duplex (assistant DNA/trigger DNA duplex) probe with a single-stranded part and DNA polymerase. Two probes coexist stably in the absence of target, and the dye exhibits relatively low FP background. Upon recognition and binding with a target protein, the stem of the aptamer hairpin probe is opened, after which the opened hairpin probe hybridizes with the single-stranded part in the PS NP-modified DNA duplex probe and triggers the CSDA reaction through the polymerase-catalyzed recycling of both target protein and trigger DNA. Throughout this CSDA process, numerous massive dyes are assembled onto PS NPs, which results in a substantial FP increase that provides a readout signal for the amplified sensing process. Our newly proposed amplified FP aptasensor enables the quantitative measurement of proteins with the detection limit in attomolar range, which is about 6 orders of magnitude lower than that of traditional homogeneous aptasensors. Moreover, this sensing method also exhibits high specificity for target proteins and can be performed in homogeneous solutions. In addition, the suitability of this method for the quantification of target protein in biological samples has also been shown. Considering these distinct advantages, the proposed sensing method can be expected to provide an ultrasensitive platform for the analysis of various types of target molecules.

  13. Discovery of PF-06928215 as a high affinity inhibitor of cGAS enabled by a novel fluorescence polarization assay

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Justin; Brault, Amy; Vincent, Fabien; Weng, Shawn; Wang, Hong; Dumlao, Darren; Aulabaugh, Ann; Aivazian, Dikran; Castro, Dana; Chen, Ming; Culp, Jeffrey; Dower, Ken; Gardner, Joseph; Hawrylik, Steven; Golenbock, Douglas; Hepworth, David; Horn, Mark; Jones, Lyn; Jones, Peter; Latz, Eicke; Li, Jing; Lin, Lih-Ling; Lin, Wen; Lin, David; Lovering, Frank; Niljanskul, Nootaree; Nistler, Ryan; Pierce, Betsy; Plotnikova, Olga; Schmitt, Daniel; Shanker, Suman; Smith, James; Snyder, William; Subashi, Timothy; Trujillo, John; Tyminski, Edyta; Wang, Guoxing; Wong, Jimson; Lefker, Bruce; Dakin, Leslie; Leach, Karen (UMASS, MED); (Pfizer)

    2017-09-21

    Cyclic GMP-AMP synthase (cGAS) initiates the innate immune system in response to cytosolic dsDNA. After binding and activation from dsDNA, cGAS uses ATP and GTP to synthesize 2', 3' -cGAMP (cGAMP), a cyclic dinucleotide second messenger with mixed 2'-5' and 3'-5' phosphodiester bonds. Inappropriate stimulation of cGAS has been implicated in autoimmune disease such as systemic lupus erythematosus, thus inhibition of cGAS may be of therapeutic benefit in some diseases; however, the size and polarity of the cGAS active site makes it a challenging target for the development of conventional substrate-competitive inhibitors. We report here the development of a high affinity (KD = 200 nM) inhibitor from a low affinity fragment hit with supporting biochemical and structural data showing these molecules bind to the cGAS active site. We also report a new high throughput cGAS fluorescence polarization (FP)-based assay to enable the rapid identification and optimization of cGAS inhibitors. This FP assay uses Cy5-labelled cGAMP in combination with a novel high affinity monoclonal antibody that specifically recognizes cGAMP with no cross reactivity to cAMP, cGMP, ATP, or GTP. Given its role in the innate immune response, cGAS is a promising therapeutic target for autoinflammatory disease. Our results demonstrate its druggability, provide a high affinity tool compound, and establish a high throughput assay for the identification of next generation cGAS inhibitors.

  14. Photoionization of the 4d10 subshell of cadmium: Photoelectron angular distributions and polarization of fluorescence radiation

    Science.gov (United States)

    Theodosiou, Constantine E.; Starace, Anthony F.; Tambe, B. R.; Manson, Steven T.

    1981-07-01

    Relativistic Dirac-Fock calculations are presented for the photoelectron angular distribution asymmetry parameter β corresponding to 4d-subshell photoionization in Cd and for the linear polarization PL of the subsequent fluorescence radiation, for photon energies less than 185 eV. Near threshold, our results for β lie lower than previous relativistic Dirac-Slater and nonrelativistic many-body-perturbation-theory (MBPT) calculations. The agreement with very recent measurements by Heinzmann and Schönhense is very good. Our calculations show that PL(2D52-->2P32)=-0.059 and -0.058 at incident photon energies hν=40.2 and 45.6 eV, respectively. These results lie above the nonrelativistic independent-electron theory absolute maximum of -0.061 for PL, but the agreement with recent measurements lying above this maximum is still not very good. Except for this peaking of PL(2D52-->2P32) above the nonrelativistic theory maximum for 40.2Kelly. We also find that PL(2D32-->2P32)=+ 0.134 at hν=21.2 eV, in excellent agreement with the experimental value of + 0.12+/-0.04 of Caldwell and Zare.

  15. Role of Solvent Polarity and Hydrogen-Bonding on Excited-State Fluorescence of 3-[(E)-{4-[Dimethylamino]benzylidene}amino]-2-naphthoic Acid (DMAMN): Isomerization vs Rotomerization.

    Science.gov (United States)

    Al-Ansari, Ibrahim Ahmed Z

    2018-02-22

    The present experimental and theoretical study on a new chromophore DMAMN of the type push-π-pull (push = dimethylaniline, π = imine, pull = 2-naphthoic acid), allows understanding of the mechanism by which the molecular conformational undergoes isomerization/rotomerization following electronic excitation. The steady-state fluorescence spectra of this compound, carried out in solvents of different polarities and proticities, showed significant changes in both the shape and peak positions. The wavelength and intensity change depend on the polarity and hydrogen-bonding environment. In highly polar solvents, the emission is weak and red-shifted compared to that for cyclohexane, but it is more red-shifted in moderate aprotic polar solvents. In hydroxyl solvents, a new weak low-energy emission band appears at ∼525 nm, attributed to the intermolecularly H-bonded open conformer. On the basis of the generated potential energy landscapes of the ground state and low-lying excited state in the gas phase and solution, we found that selective photon absorption, brings this molecule to a "bright" state, from which N═C isomerization Z → E, takes place. This isomerization in gas-phase and low-polarity solvents leads to two minima with a barrier, whereas in highly polar-protic media, it gives one minimum on the S 1 surface with low ΔE S1/T1 (0.17 eV), facilitating deactivation via ISC.

  16. [Fluorescence polarization used to investigate the cell membrane fluidity of Saccharomyces cerevisiae treated by pulsed electric field].

    Science.gov (United States)

    Zhang, Ying; Zeng, Xin-An; Wen, Qi-Biao; Li, Lin

    2008-01-01

    To know the lethal mechanism of microorganisms under pulsed electric field treatment, the relationship between the inactivation of Saccharomyces cerevisiae (CICC1308) cell and the permeability and fluidity changes of its cell membrane treated by pulsed electric field (0-25 kV x cm(-1), 0-266 ms) was investigated. With 1,6-diphenyl-1,3,5-hexatriene (DPH) used as a probe, the cell membrane fluidity of Saccharomyces cerevisiae treated by pulsed electric field was expressed by fluorescence polarization. Results showed that the cell membrane fluidity decreases when the electric flied strength is up to 5 kV x cm(-1), and decreases with the increase in electric field strength and treatment time. The plate counting method and ultraviolet spectrophotometer were used to determine the cell viability and to investigate the cell membrane permeability, respectively, treated by pulsed electric field. Results showed that the lethal ratio and the content of protein and nucleic acid leaked from intracellular plasma increased with the increase in the electric field strength and the extension of treatment time. Even in a quite lower electric field of 5 kV x cm(-1) with a tiny microorganism lethal level, the increase in UV absorption value and the decrease in fluidity were significant. It was demonstrated that the cell membrane fluidity decreases with the increase in lethal ratio and cell membrane permeability. The viscosity of cell membrane increases with the decrease in fluidity. These phenomena indicated that cell membrane is one of the most key sites during the pulsed electric field treatment, and the increased membrane permeability and the decreased cell membrane fluidity contribute to the cell death.

  17. Sensitive diagnosis of bovine tuberculosis in a farmed cervid herd with use of an MPB70 protein fluorescence polarization assay.

    Science.gov (United States)

    Surujballi, Om; Lutze-Wallace, Cyril; Turcotte, Claude; Savic, Mirjana; Stevenson, Dan; Romanowska, Anna; Monagle, Wendy; Berlie-Surujballi, Gloria; Tangorra, Erin

    2009-07-01

    After histopathological examination of a lesion found in a herd member returned a diagnosis of mycobacteriosis, a farmed herd (n = 47) of elk (Cervus elaphus nelsoni) and red deer (C. elaphus elaphus) was investigated for bovine tuberculosis with a battery of antemortem and postmortem diagnostic tests. Every animal was tested with the mid-cervical tuberculin skin test; all 47 had negative results. All of the 16 adult animals and 15 of the 31 calves (approximately 2-years-old) were blood-tested with a lymphocyte stimulation test (LST) and a fluorescence polarization assay (FPA), which detects antibody to the MPB70 protein antigen. At necropsy of the 31 blood-tested animals, tissues were harvested for histopathological examination and culture of mycobacteria. Mycobacterium bovis was isolated from 16 of the 31 animals, and a scotochromogen was also isolated from 1 of the 16 whose tissues yielded M. bovis. Each of these 16 animals, 15 of which were calves, also received a histopathological diagnosis of mycobacteriosis. Other species of mycobacteria, including those belonging to the M. avium and M. terrae complexes, were isolated from an additional 7 animals. The FPA was scored "positive" or "suspect" for 16 animals, 13 (81%) of which were culture-positive for M. bovis. The other 3 animals that were culture-positive for M. bovis had negative FPA results. Of the 3 FPA-positive or FPA-suspect animals that were culture-negative, 2 were suspected to have mycobacteriosis on the basis of the histopathological examination. The 7 animals from which Mycobacterium species other than M. bovis were cultured were all FPA-negative. The only animal with positive LST results was also FPA-positive and culture-positive for M. bovis. The M. bovis isolates had an identical spoligotype pattern, with an octal code of 664073777777600. This is the first report of the isolation and identification of this strain type in Canada.

  18. Mechanism of Lipid Binding of Human Apolipoprotein E3 by Hydrogen/Deuterium Exchange/Mass Spectrometry and Fluorescence Polarization.

    Science.gov (United States)

    Fabilane, Charina S; Nguyen, Patricia N; Hernandez, Roy V; Nirudodhi, Sasidhar; Duong, Mai; Maier, Claudia S; Narayanaswami, Vasanthy

    2016-01-01

    Human apolipoprotein E3 (apoE3) is an exchangeable apolipoprotein that plays a critical role in maintaining plasma cholesterol/triglyceride homeostasis. The C-terminal (CT) domain of apoE3 (residues 201-299) is composed of amphipathic α-helices C1: W210-S223, C2: V236-E266, and C3: D271-W276, which play a dominant role in mediating high-affinity lipid binding. The objective is to understand the accessibility of the CT domain at the sub-domain level and the mechanistic details regarding lipid-binding interaction. Hydrogen-deuterium exchange coupled to mass spectrometry (HDX/MS) of recombinant wild type (WT) apoE(201-299), chemical-induced unfolding monitored as changes in fluorescence polarization (FP) of labeled apoE(201-299) bearing a probe at specified sites, and lipid binding studies were carried out. HDX/MS revealed that residues towards the C-terminal end of the domain display significantly lower %D uptake compared to those towards the center, suggesting extensive protein-protein interaction in this segment. Functional assays showed that locking apoE(201-299) in an inter-molecular disulfide-bonded state at position 209, 223, 255, or 277 significantly decreases its ability to interact with lipids, especially when tethered towards the ends; this could be restored by reduction. Unfolding studies indicate that the C-terminal end offers less resistance to unfolding compared to the central portion of the domain. Taken together, our data suggest that two dimers of CT domain are juxtaposed around helix C3 leading to apoE3 tetramerization, and that dissociation to monomeric units is a required step in lipid binding, with helix C3 likely seeking stability via lipid interaction prior to helices C1 or C2.

  19. Intracellular Biosynthesis of Fluorescent CdSe Quantum Dots in Bacillus subtilis: A Strategy to Construct Signaling Bacterial Probes for Visually Detecting Interaction Between Bacillus subtilis and Staphylococcus aureus.

    Science.gov (United States)

    Yan, Zheng-Yu; Ai, Xiao-Xia; Su, Yi-Long; Liu, Xin-Ying; Shan, Xiao-Hui; Wu, Sheng-Mei

    2016-02-01

    In this work, fluorescent Bacillus subtilis (B. subtilis) cells were developed as probes for imaging applications and to explore behaviorial interaction between B. subtilis and Staphylococcus aureus (S. aureus). A novel biological strategy of coupling intracellular biochemical reactions for controllable biosynthesis of CdSe quantum dots by living B. subtilis cells was demonstrated, through which highly luminant and photostable fluorescent B. subtilis cells were achieved with good uniformity. With the help of the obtained fluorescent B. subtilis cells probes, S. aureus cells responded to co-cultured B. subtilis and to aggregate. The degree of aggregation was calculated and nonlinearly fitted to a polynomial model. Systematic investigations of their interactions implied that B. subtilis cells inhibit the growth of neighboring S. aureus cells, and this inhibition was affected by both the growth stage and the amount of surrounding B. subtilis cells. Compared to traditional methods of studying bacterial interaction between two species, such as solid culture medium colony observation and imaging mass spectrometry detection, the procedures were more simple, vivid, and photostable due to the efficient fluorescence intralabeling with less influence on the cells' surface, which might provide a new paradigm for future visualization of microbial behavior.

  20. A fluorescent paramagnetic Mn metal–organic framework based on semi-rigid pyrene tetracarboxylic acid: sensing of solvent polarity and explosive nitroaromatics

    Directory of Open Access Journals (Sweden)

    Alankriti Bajpai

    2015-09-01

    Full Text Available An Mn metal–organic framework (Mn-MOF, Mn-L, based on a pyrene-tetraacid linker (H4L, displays a respectable fluorescence quantum yield of 8.3% in spite of the presence of the paramagnetic metal ions, due presumably to fixation of the metal ions in geometries that do not allow complete energy/charge-transfer quenching. Remarkably, the porous Mn-L MOF with ∼25% solvent-accessible volume exhibits a heretofore unprecedented solvent-dependent fluorescence emission maximum, permitting its use as a probe of solvent polarity; the emission maxima in different solvents correlate excellently with Reichardt's solvent polarity parameter (ETN. Further, the applicability of Mn-L to the sensing of nitroaromatics via fluorescence quenching is demonstrated; the detection limit for TNT is shown to be 125 p.p.m. The results bring out the fact that MOFs based on paramagnetic metal ions can indeed find application when the quenching mechanisms are attenuated by certain geometries of the organic linkers of the MOF.

  1. Modulation of dual fluorescence in a 3-hydroxyquinolone dye by perturbation of its intramolecular proton transfer with solvent polarity and basicity.

    Science.gov (United States)

    Yushchenko, Dmytro A; Shvadchak, Volodymyr V; Bilokin', Mykhailo D; Klymchenko, Andrey S; Duportail, Guy; Mély, Yves; Pivovarenko, Vasyl G

    2006-11-01

    A representative of a new class of dyes with dual fluorescence due to an excited state intramolecular proton transfer (ESIPT) reaction, namely 1-methyl-2-(4-methoxy)phenyl-3-hydroxy-4(1H)-quinolone (QMOM), has been studied in a series of solvents covering a large range of polarity and basicity. A linear dependence of the logarithm of its two bands intensity ratio, log(I(N*)/I(T*)), upon the solvent polarity expressed as a function of the dielectric constant, (epsilon- 1)/(2epsilon + 1), is observed for a series of protic solvents. A linear dependence for log(I(N*)/I(T*)) is also found in aprotic solvents after taking into account the solvent basicity. In contrast, the positions of the absorption and the two emission bands of QMOM do not noticeably depend on the solvent polarity and basicity, indicating relatively small changes in the transition moment of QMOM upon excitation and emission. Time-resolved experiments in acetonitrile, ethyl acetate and dimethylformamide suggest an irreversible ESIPT reaction for this dye. According to the time-resolved data, an increase of solvent basicity results in a dramatic decrease of the ESIPT rate constant, probably due to the disruption of the intramolecular H-bond of the dye by the basic solvent. Due to this new sensor property, 3-hydroxyquinolones are promising candidates for the development of a new generation of environment-sensitive fluorescence dyes for probing interactions of biomolecules.

  2. Tip-enhanced fluorescence with radially polarized illumination for monitoring loop-mediated isothermal amplification on Hepatitis C virus cDNA

    Science.gov (United States)

    Wei, Shih-Chung; Chuang, Tsung-Liang; Wang, Da-Shin; Lu, Hui-Hsin; Gu, Frank X.; Sung, Kung-Bin; Lin, Chii-Wann

    2015-02-01

    A tip nanobiosensor for monitoring DNA replication was presented. The effects of excitation power and polarization on tip-enhanced fluorescence (TEF) were assessed with the tip immersed in fluorescein isothiocyanate solution first. The photon count rose on average fivefold with radially polarized illumination at 50 mW. We then used polymerase-functionalized tips for monitoring loop-mediated isothermal amplification on Hepatitis C virus cDNA. The amplicon-SYBR Green I complex was detected and compared to real-time loop-mediated isothermal amplification. The signals of the reaction using 4 and 0.004 ng/μl templates were detected 10 and 30 min earlier, respectively. The results showed the potential of TEF in developing a nanobiosensor for real-time DNA amplification.

  3. Alignment of Solutes in Stretched Polyethylene. Determination of the Five Second and Fourth Moments of the Orientation Distribution of 2-Fluoropyrene from Polarized Fluorescence

    DEFF Research Database (Denmark)

    Langkilde, Frans W.; Gisin, Markus; Thulstrup, Erik W.

    1983-01-01

    Measurements of linear dichroism and of polarized fluorescence of 2-fluoropyrene (2-F-1) in stretched linear low-density polyethylene (LLDPE) at 77K have been used to evaluate the two independent second moments, 〈cos2 z〉 and 〈cos2 y〉, as well as the three independent fourth moments, 〈cos4 z〉, 〈cos4...... y〉, and 〈cos4 x〉, of the orientation distribution function. The results are used to discuss two previously proposed detailed models for the mechanism of the orientation of aromatics in stretched polyethylene. For pyrene (1) and 2-methylpyrene (2-Me-1), four of the five moments were obtained...

  4. A fluorescence polarization assay to quantify biotin and biotin-binding proteins in whole plant extracts using Alexa-Fluor 594 biocytin.

    Science.gov (United States)

    Martin, Harry; Murray, Colleen; Christeller, John; McGhie, Tony

    2008-10-01

    A high-throughput fluorescence polarization assay has been developed for the detection of biotin and biotin-binding proteins in whole leaf extracts. Various groups are investigating the insecticidal properties of avidin and other biotin-binding proteins expressed in leaves of transgenic plants. The methods commonly used to quantify biotin and avidin in leaf extracts are enzyme-linked immunosorbent assay (ELISA) and Western blotting. Here we describe a homogeneous fluorescence polarization (FP) method that quantifies transgenic avidin in whole leaf extract by the simple addition of the fluorescent avidin ligand Alexa-Fluor 594 biocytin (AFB). The FP assay exploits the fact that AFB excites and emits in regions of the spectrum that are relatively free of background fluorescence in leaf extract. Transgenic leaf avidin can be quantified within 1-2 h by the FP method, in comparison with 1-2 days for ELISA and Western blotting. The FP method can also measure the amount of biotin in control leaves, not expressing avidin. Functional avidin levels of 1.54 microM (26.1 microg/g leaf tissue) were detected in tobacco leaves expressing vacuole-targeted avidin. Control leaves had biotin levels of around 0.74 microM (approximately 0.18 microg/g leaf tissue). Reagent costs are minimal: typically AFB is used at concentrations of 1-10 nM, avidin is used at 1-100 nM, and sample volumes are 20 microL in 384-well microplates.

  5. Trials and Tribulations of Fluorescent Dissolved Organic Matter Chemical Interpretations: A case study of polar ice cores

    Science.gov (United States)

    D'Andrilli, J.

    2017-12-01

    Excitation emission matrix fluorescence spectroscopy is widely applied for rapid dissolved organic matter (DOM) characterization in aquatic systems. Fluorescent DOM surveys are booming, not only as a central focus in aquatic environments, but also as an important addition to interdisciplinary research (e.g., DOM analysis in concert with ice core paleoclimate reconstructions, stream metabolism, hydrologic regimes, agricultural developments, and biological activity), opening new doors, not just for novelty, but also for more challenges with chemical interpretations. Recently, the commonly used protein- versus humic-like classifications of DOM have been ineffective at describing DOM chemistry in various systems (e.g., ice cores, wastewaters, incubations/engineered). Moreover, the oversimplification of such classifications used to describe fluorescing components, without further scrutiny, has become commonplace, ultimately producing vague reporting. For example, West Antarctic ice core DOM was shown to contain fluorescence in the low excitation/emission wavelength region, however resolved fluorophores depicting tyrosine- and tryptophan-like DOM were not observed. At first, as literature suggested, we reported this result as protein-like, and concluded that microbial contributions were dominant in deep ice. That initial interpretation would disintegrate the conservation paradigm of atmospheric composition during deposition, the crux of ice core research, and contradict other lines of evidence. This begged the question, "How can we describe DOM chemistry without distinct fluorophores?" Antarctic ice core DOM was dominated by neither tyrosine- nor tryptophan-like fluorescence, causing "unusual" looking fluorescent components. After further examination, deep ice DOM was reported to contain fluorescent species most similar to monolignols and tannin-like phenols, describing the precursors of lignin from low carbon producing environments, consistent with marine sediment

  6. Visualization of polarized membrane type 1 matrix metalloproteinase activity in live cells by fluorescence resonance energy transfer imaging

    NARCIS (Netherlands)

    Ouyang, Mingxing; Lu, Shaoying; Li, Xiao-Yan; Xu, Jing; Seong, Jihye; Giepmans, Ben N. G.; Shyy, John Y. -J.; Weiss, Stephen J.; Wang, Yingxiao

    2008-01-01

    Membrane type 1 matrix metalloproteinase (MT1-MMP) plays a critical role in cancer cell biology by proteolytically remodeling the extracellular matrix. Utilizing fluorescence resonance energy transfer ( FRET) imaging, we have developed a novel biosensor, with its sensing element anchoring at the

  7. Ratios of regioisomers of minor acylglycerols less polar than triricinolein in castor oil estimated by mass spectrometry and the biosynthesis of tetraacylglycerols in castor

    Science.gov (United States)

    We have recently reported the identification of forty new minor molecular species of acylglycerols containing hydroxy fatty acids less polar than triricinolein by electrospray ionization mass spectrometry of the lithium adducts. The ratios of regioisomers of triacylglycerols (ABC and AAB types) and ...

  8. An investigation into the role of macromolecules of different polarity as passivating agent on the physical, chemical and structural properties of fluorescent carbon nanodots

    Science.gov (United States)

    Alas, Melis Ozge; Genc, Rukan

    2017-05-01

    In this study, comparative evaluation of fluorescent carbon nanodots (C-Dots) prepared using carob molasses was reported by screening various biocompatible macromolecules as passivating agent (PA). Incorporation of PAs with different molecular weight, polarity, and chemical structure was examined, and compared with the polyethylene glycol (PEG, Mn = 10 kN) passivated and pristine C-Dots. Not only the fluorescence properties but also many other features including size, crystal structure, colloidal conductivity, resistance to photobleaching, quantum yield, and UV-modulated surface interaction of them with the reactive oxygen species (ROS) as well as ROS production were investigated. Photoluminescence (PL) capacity of C-Dots was found to be associated with the number of surface alkyl groups and polymeric hydrogen bounding present on the C-Dot surface (increased number is associated with decreased PL) while surface conductivity of C-Dots in water was proportional to the PL intensity. More importantly, C-Dots with relatively poorer fluorescent were investigated in various organic solvents (hexane, methanol, acetone, ethanol, dimethylformamide (DMF), and DMSO). As happens with the fluorescent dyes, their PL intensities were significantly enhanced (even for pristine C-Dots) depending on the solvent characteristics. All of the C-Dots synthesized were further evaluated by means of UV-induced generation of ROS and inhibition of ROS by using H2O2 as model. In contrary to other carbonaceous nanomaterials, they did not show any ROS generation, on the contrary, they showed ROS scavenging activity that can be modulated by UV-irradiation ( λ exc = 365 nm). PEG and alginate passivated C-Dots inhibited H2O2 activity at LC50 values below 10 mg/mL.

  9. Novel Alexa Fluor-488 labeled antagonist of the A(2A) adenosine receptor: Application to a fluorescence polarization-based receptor binding assay.

    Science.gov (United States)

    Kecskés, Miklós; Kumar, T Santhosh; Yoo, Lena; Gao, Zhan-Guo; Jacobson, Kenneth A

    2010-08-15

    Fluorescence polarization (FP) assay has many advantages over the traditional radioreceptor binding studies. We developed an A(2A) adenosine receptor (AR) FP assay using a newly synthesized fluorescent antagonist of the A(2A)AR (MRS5346), a pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine derivative conjugated to the fluorescent dye Alexa Fluor-488. MRS5346 displayed a K(i) value of 111+/-16nM in radioligand binding using [(3)H]CGS21680 and membranes prepared from HEK293 cells stably expressing the human A(2A)AR. In a cyclic AMP functional assay, MRS5346 was shown to be an A(2A)AR antagonist. MRS5346 did not show any effect on A(1) and A(3) ARs in binding or the A(2B)AR in a cyclic AMP assay at 10microM. Its suitability as a fluorescent tracer was indicated in an initial observation of an FP signal following A(2A)AR binding. The FP signal was optimal with 20nM MRS5346 and 150microg protein/mL HEK293 membranes. The association and dissociation kinetic parameters were readily determined using this FP assay. The K(d) value of MRS5346 calculated from kinetic parameters was 16.5+/-4.7nM. In FP competition binding experiments using MRS5346 as a tracer, K(i) values of known AR agonists and antagonists consistently agreed with K(i) values from radioligand binding. Thus, this FP assay, which eliminates using radioisotopes, appears to be appropriate for both routine receptor binding and high-throughput screening with respect to speed of analysis, displaceable signal and precision. The approach used in the present study could be generally applicable to other GPCRs. Published by Elsevier Inc.

  10. Alignment of Ar{sup +} [{sup 3}P]4p{sup 2}P{sup 0}{sub 3/2} satellite state from the polarization analysis of fluorescent radiation after photoionization

    Energy Technology Data Exchange (ETDEWEB)

    Yenen, O.; McLaughlin, K.W.; Jaecks, D.H. [Univ. of Nebraska, Lincoln, NE (United States)] [and others

    1997-04-01

    The measurement of the polarization of radiation from satellite states of Ar{sup +} formed after the photoionization of Ar provides detailed information about the nature of doubly excited states, magnetic sublevel cross sections and partial wave ratios of the photo-ejected electrons. Since the formation of these satellite states is a weak process, it is necessary to use a high flux beam of incoming photons. In addition, in order to resolve the many narrow doubly excited Ar resonances, the incoming photons must have a high resolution. The characteristics of the beam line 9.0.1 of the Advanced Light Source fulfill these requirements. The authors determined the polarization of 4765 {Angstrom} fluorescence from the Ar{sup +} [{sup 3}P] 4p {sup 2}P{sub 3/2}{sup 0} satellite state formed after photoionization of Ar by photons from the 9.0.1 beam line of ALS in the 35.620-38.261 eV energy range using a resolution of approximately 12,700. This is accomplished by measuring the intensities of the fluorescent light polarized parallel (I{parallel}) and perpendicular (I{perpendicular}) to the polarization axis of the incident synchrotron radiation using a Sterling Optics 105MB polarizing filter. The optical system placed at 90{degrees} with respect to the polarization axis of the incident light had a narrow band interference filter ({delta}{lambda}=0.3 nm) to isolate the fluorescent radiation.

  11. Biosynthesis of Fluorescent Bi2S3 Nanoparticles and their Application as Dual-Function SPECT-CT Probe for Animal Imaging.

    Science.gov (United States)

    Uddin, Imran; Ahmad, Absar; Siddiqui, Ejaz Ahmad; Rahaman, Sk Hasanur; Gambhir, Sanjay

    2016-01-01

    Bismuth sulphide (Bi2S3) is an excellent semiconductor and its nanoparticles have numerous significant applications including photovoltaic materials, photodiode arrays, bio-imaging, etc. Nevertheless, these nanoparticles when fabricated by chemical and physical routes tend to easily aggregate in colloidal solutions, are eco-unfriendly, cumbrous and very broad in size distribution. The aim of the present manuscript was to ecologically fabricate water dispersible, safe and stable Bi2S3 nanoparticles such that these may find use in animal imaging, diagnostics, cell labeling and other biomedical applications. Herein, we for the first time have biosynthesized highly fluorescent, natural protein capped Bi2S3 nanoparticles by subjecting the fungus Fusarium oxysporum to bismuth nitrate pentahydrate [Bi(NO3)3.5H2O] alongwith sodium sulphite (Na2SO3) as precursor salts under ambient conditions of temperature, pressure and pH. The nanoparticles were completely characterized using recognized standard techniques. These natural protein capped Bi2S3 nanoparticles are quasi-spherical in shape with an average particle size of 15 nm, maintain long term stability and show semiconductor behavior having blue shift with a band gap of 3.04 eV. Semiconductor nanocrystals are fundamentally much more fluorescent than the toxic fluorescent chemical compounds (fluorophores) which are presently largely employed in imaging, immunohistochemistry, biochemistry, etc. Biologically fabricated fluorescent nanoparticles may replace organic fluorophores and aid in rapid development of biomedical nanotechnology. Thus, biodistribution study of the so-formed Bi2S3 nanoparticles in male Sprague Dawley rats was done by radiolabelling with Technitium-99m (Tc-99m) and clearance time from blood was calculated. The nanoparticles were then employed in SPECT-CT probe for animal imaging where these imparted iodine equivalent contrast.

  12. Analysis of trace element compositions in adhesive cloth tapes using high-energy x-ray fluorescence spectrometer with three-dimensional polarization optics for forensic discrimination

    International Nuclear Information System (INIS)

    Goto, Akiko; Hokura, Akiko; Nakai, Izumi

    2008-01-01

    The forensic discrimination of adhesive cloth tapes often used in crimes was developed using a high-energy energy-dispersive X-ray fluorescence spectrometer with 3-dimensional polarization optics. The best measurement condition for discrimination of the tape was as follows: secondary targets, Rh and Al 2 O 3 ; measurement time, 300 s for Rh and 600 s for Al 2 O 3 ; 14 elements (Ca, Ti, Cr, Mn, Fe, Ni, Zn, Sr, Zr, Nb, Mo, Sb, Ba and Pb) were used for discrimination. It is found that the combined information of yarn density and the XRF peak intensity of the 14 elements successfully discriminated 29 out of 31 samples, of which 2 probably had the same origin. This technique is useful for forensic analysis, because it is nondestructive, rapid and easy. Therefore, it can be applied to actual forensic identification. (author)

  13. Fluorescence microscopy is superior to polarized microscopy for detecting amyloid deposits in Congo red-stained trephine bone marrow biopsy specimens.

    Science.gov (United States)

    Marcus, Alan; Sadimin, Evita; Richardson, Maurice; Goodell, Lauri; Fyfe, Billie

    2012-10-01

    The classic gold standard for detecting amyloid deposits is Congo red-stained bright field and polarized microscopy (CRPM). A prior study showed that Congo red fluorescence (CRF) microscopy had increased sensitivity compared with traditional CRPM when analyzing fat pad specimens. The purpose of the current study was to determine the sensitivity of CRF for evaluating Congo red-stained bone marrow biopsy specimens, and to compare these results with those of CRPM. We compared the CRPM and the CRF analyses of 33 trephine bone marrow biopsy specimens with clinical or morphologic suspicion of amyloid deposits. These results were verified against immunohistochemical staining with anti-amyloid P antibody. CRF achieved 100% sensitivity, and CRPM achieved 75% sensitivity. Both groups showed 100% specificity compared with amyloid P immunohistochemical staining. The results show that CRF is a sensitive method to analyze trephine bone marrow biopsy specimens for amyloid deposits.

  14. Study of ciclosporine blood levels in patients after kidney or bone-marrow transplantation. Comparison between the two methods, fluorescence polarization immunoassay and radioimmunoassay

    International Nuclear Information System (INIS)

    Sadeg, N.; Pham Huy, C.; Claude, J.R.; Postaire, M.; Lebrec, H.; Hamon, M.; Broyer, M.; Gagnadoux, M.F.; Fischer, A.

    1989-01-01

    The apparition of ciclosporine, immunodepressive drug, has largely improved the organ transplantations. However, the range of blood concentrations must be defined to allow the efficacity of ciclosporine therapy and to avoid toxic reactions, because there are very important variations for a same dosage according to the individuals and the diseases. Relative to the low concentrations to be determined (about one hundred ng/ml), the most useful methods for ciclosporine measurement are based on immunochemical assays. This work compares the two methods: radioimmunoassay (RIA) and fluorescence polarization immunoassay (FPIA) simultaneously performed on several hundred samples. A very significant correlation exists between the two techniques (r = 0.80). The advantages of immunofluorescent assay consists in rapidity, sensibility and facility to realize emergency analysis [fr

  15. Portable ultrahigh-vacuum sample storage system for polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Yoshihide, E-mail: e0827@mosk.tytlabs.co.jp; Nishimura, Yusaku F.; Suzuki, Ryo; Beniya, Atsushi; Isomura, Noritake [Toyota Central R& D Labs., Inc., Yokomichi 41-1, Nagakute, Aichi 480-1192 (Japan); Uehara, Hiromitsu; Asakura, Kiyotaka; Takakusagi, Satoru [Catalysis Research Center, Hokkaido University, Kita 21-10, Sapporo, Hokkaido 001-0021 (Japan); Nimura, Tomoyuki [AVC Co., Ltd., Inada 1450-6, Hitachinaka, Ibaraki 312-0061 (Japan)

    2016-03-15

    A portable ultrahigh-vacuum sample storage system was designed and built to investigate the detailed geometric structures of mass-selected metal clusters on oxide substrates by polarization-dependent total-reflection fluorescence x-ray absorption fine structure spectroscopy (PTRF-XAFS). This ultrahigh-vacuum (UHV) sample storage system provides the handover of samples between two different sample manipulating systems. The sample storage system is adaptable for public transportation, facilitating experiments using air-sensitive samples in synchrotron radiation or other quantum beam facilities. The samples were transferred by the developed portable UHV transfer system via a public transportation at a distance over 400 km. The performance of the transfer system was demonstrated by a successful PTRF-XAFS study of Pt{sub 4} clusters deposited on a TiO{sub 2}(110) surface.

  16. Sorting Out Antibiotics' Mechanisms of Action: a Double Fluorescent Protein Reporter for High-Throughput Screening of Ribosome and DNA Biosynthesis Inhibitors.

    Science.gov (United States)

    Osterman, Ilya A; Komarova, Ekaterina S; Shiryaev, Dmitry I; Korniltsev, Ilya A; Khven, Irina M; Lukyanov, Dmitry A; Tashlitsky, Vadim N; Serebryakova, Marina V; Efremenkova, Olga V; Ivanenkov, Yan A; Bogdanov, Alexey A; Sergiev, Petr V; Dontsova, Olga A

    2016-12-01

    In order to accelerate drug discovery, a simple, reliable, and cost-effective system for high-throughput identification of a potential antibiotic mechanism of action is required. To facilitate such screening of new antibiotics, we created a double-reporter system for not only antimicrobial activity detection but also simultaneous sorting of potential antimicrobials into those that cause ribosome stalling and those that induce the SOS response due to DNA damage. In this reporter system, the red fluorescent protein gene rfp was placed under the control of the SOS-inducible sulA promoter. The gene of the far-red fluorescent protein, katushka2S, was inserted downstream of the tryptophan attenuator in which two tryptophan codons were replaced by alanine codons, with simultaneous replacement of the complementary part of the attenuator to preserve the ability to form secondary structures that influence transcription termination. This genetically modified attenuator makes possible Katushka2S expression only upon exposure to ribosome-stalling compounds. The application of red and far-red fluorescent proteins provides a high signal-to-background ratio without any need of enzymatic substrates for detection of the reporter activity. This reporter was shown to be efficient in high-throughput screening of both synthetic and natural chemicals. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  17. Identification of Small-Molecule Inhibitors of the HuR/RNA Interaction Using a Fluorescence Polarization Screening Assay Followed by NMR Validation.

    Directory of Open Access Journals (Sweden)

    Zhonghua Wang

    Full Text Available The human antigen R (HuR stabilizes many mRNAs of proto-oncogene, transcription factors, cytokines and growth factors by recognizing AU-rich elements (AREs presented in their 3' or 5' untranslated region (UTR. Multiple lines of experimental evidence suggest that this process plays a key role in cancer development. Thus, destabilizing HuR/RNA interaction by small molecules presents an opportunity for cancer treatment/prevention. Here we present an integrated approach to identify inhibitors of HuR/RNA interaction using a combination of fluorescence-based and NMR-based high throughput screening (HTS. The HTS assay with fluorescence polarization readout and Z'-score of 0.8 was used to perform a screen of the NCI diversity set V library in a 384 well plate format. An NMR-based assay with saturation transfer difference (STD detection was used for hits validation. Protein NMR spectroscopy was used to demonstrate that some hit compounds disrupt formation of HuR oligomer, whereas others block RNA binding. Thus, our integrated high throughput approach provides a new avenue for identification of small molecules targeting HuR/RNA interaction.

  18. A fluorescence polarization based screening assay for identification of small molecule inhibitors of the PICK1 PDZ domain

    DEFF Research Database (Denmark)

    Thorsen, Thor S; Madsen, Kenneth L; Dyhring, Tino

    2011-01-01

    domain in PICK1 (protein interacting with C kinase 1). We screened 43,380 compounds for their ability to inhibit binding of an Oregon Green labeled C-terminal dopamine transporter peptide (OrG-DAT C13) to purified PICK1 in solution. The assay was highly reliable with excellent screening assay parameters...... (Z'˜0.7 and Z˜0.6). Out of ~200 compounds that reduced FP to less than 80% of the control wells, six compounds were further characterized. The apparent affinities of the compounds were determined in FP competition binding experiments and ranged from ~5.0 µM to ~193 µM. Binding to the PICK1 PDZ domain...... to fluorescence resonance energy transfer (FRET) experiments capable of inhibiting the interaction between the C-terminus of the GluR2 subunit of the AMPA-type glutamate receptor and PICK1 in live cells. Additional experiments suggested that CSC-03 most likely is an irreversible inhibitor but with specificity...

  19. Fluorescence polarization measures energy funneling in single light-harvesting antennas--LH2 vs conjugated polymers.

    Science.gov (United States)

    Camacho, Rafael; Tubasum, Sumera; Southall, June; Cogdell, Richard J; Sforazzini, Giuseppe; Anderson, Harry L; Pullerits, Tõnu; Scheblykin, Ivan G

    2015-10-19

    Numerous approaches have been proposed to mimic natural photosynthesis using artificial antenna systems, such as conjugated polymers (CPs), dendrimers, and J-aggregates. As a result, there is a need to characterize and compare the excitation energy transfer (EET) properties of various natural and artificial antennas. Here we experimentally show that EET in single antennas can be characterized by 2D polarization imaging using the single funnel approximation. This methodology addresses the ability of an individual antenna to transfer its absorbed energy towards a single pool of emissive states, using a single parameter called energy funneling efficiency (ε). We studied individual peripheral antennas of purple bacteria (LH2) and single CP chains of 20 nm length. As expected from a perfect antenna, LH2s showed funneling efficiencies close to unity. In contrast, CPs showed lower average funneling efficiencies, greatly varying from molecule to molecule. Cyclodextrin insulation of the conjugated backbone improves EET, increasing the fraction of CPs possessing ε = 1. Comparison between LH2s and CPs shows the importance of the protection systems and the protein scaffold of LH2, which keep the chromophores in functional form and at such geometrical arrangement that ensures excellent EET.

  20. Fluorescence polarization measures energy funneling in single light-harvesting antennas—LH2 vs conjugated polymers

    Science.gov (United States)

    Camacho, Rafael; Tubasum, Sumera; Southall, June; Cogdell, Richard J.; Sforazzini, Giuseppe; Anderson, Harry L.; Pullerits, Tõnu; Scheblykin, Ivan G.

    2015-10-01

    Numerous approaches have been proposed to mimic natural photosynthesis using artificial antenna systems, such as conjugated polymers (CPs), dendrimers, and J-aggregates. As a result, there is a need to characterize and compare the excitation energy transfer (EET) properties of various natural and artificial antennas. Here we experimentally show that EET in single antennas can be characterized by 2D polarization imaging using the single funnel approximation. This methodology addresses the ability of an individual antenna to transfer its absorbed energy towards a single pool of emissive states, using a single parameter called energy funneling efficiency (ɛ). We studied individual peripheral antennas of purple bacteria (LH2) and single CP chains of 20 nm length. As expected from a perfect antenna, LH2s showed funneling efficiencies close to unity. In contrast, CPs showed lower average funneling efficiencies, greatly varying from molecule to molecule. Cyclodextrin insulation of the conjugated backbone improves EET, increasing the fraction of CPs possessing ɛ = 1. Comparison between LH2s and CPs shows the importance of the protection systems and the protein scaffold of LH2, which keep the chromophores in functional form and at such geometrical arrangement that ensures excellent EET.

  1. Tungsten disulfide nanosheet and exonuclease III co-assisted amplification strategy for highly sensitive fluorescence polarization detection of DNA glycosylase activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jingjin; Ma, Yefei [Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources of Education Ministry, Guangxi Normal University, Guilin, 541004 (China); Kong, Rongmei [The Key Laboratory of Life-Organic Analysis, College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu, Shandong 273165 (China); Zhang, Liangliang, E-mail: liangzhang319@163.com [Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources of Education Ministry, Guangxi Normal University, Guilin, 541004 (China); Yang, Wen; Zhao, Shulin [Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources of Education Ministry, Guangxi Normal University, Guilin, 541004 (China)

    2015-08-05

    Herein, we introduced a tungsten disulfide (WS{sub 2}) nanosheet and exonuclease III (Exo III) co-assisted signal amplification strategy for highly sensitive fluorescent polarization (FP) assay of DNA glycosylase activity. Two DNA glycosylases, uracil-DNA glycosylase (UDG) and human 8-oxoG DNA glycosylase 1 (hOGG1), were tested. A hairpin-structured probe (HP) which contained damaged bases in the stem was used as the substrate. The removal of damaged bases from substrate by DNA glycosylase would lower the melting temperature of HP. The HP was then opened and hybridized with a FAM dye-labeled single strand DNA (DP), generating a duplex with a recessed 3′-terminal of DP. This design facilitated the Exo III-assisted amplification by repeating the hybridization and digestion of DP, liberating numerous FAM fluorophores which could not be adsorbed on WS{sub 2} nanosheet. Thus, the final system exhibited a small FP signal. However, in the absence of DNA glycosylases, no hybridization between DP and HP was occurred, hampering the hydrolysis of DP by Exo III. The intact DP was then adsorbed on the surface of WS{sub 2} nanosheet that greatly amplified the mass of the labeled-FAM fluorophore, resulting in a large FP value. With the co-assisted amplification strategy, the sensitivity was substantially improved. In addition, this method was applied to detect UDG activity in cell extracts. The study of the inhibition of UDG was also performed. Furthermore, this method is simple in design, easy in implementation, and selective, which holds potential applications in the DNA glycosylase related mechanism research and molecular diagnostics. - Highlights: • A fluorescence polarization strategy for DNA glycosylase activity detection was developed. • The present method was based on WS{sub 2} nanosheet and exonuclease III co-assisted signal amplification. • A high sensitivity and desirable selectivity were achieved. • This method provides a promising universal platform for DNA

  2. Auxin transport sites are visualized in planta using fluorescent auxin analogs

    Science.gov (United States)

    Hayashi, Ken-ichiro; Nakamura, Shouichi; Fukunaga, Shiho; Nishimura, Takeshi; Jenness, Mark K.; Murphy, Angus S.; Motose, Hiroyasu; Nozaki, Hiroshi; Furutani, Masahiko; Aoyama, Takashi

    2014-01-01

    The plant hormone auxin is a key morphogenetic signal that controls many aspects of plant growth and development. Cellular auxin levels are coordinately regulated by multiple processes, including auxin biosynthesis and the polar transport and metabolic pathways. The auxin concentration gradient determines plant organ positioning and growth responses to environmental cues. Auxin transport systems play crucial roles in the spatiotemporal regulation of the auxin gradient. This auxin gradient has been analyzed using SCF-type E3 ubiquitin-ligase complex-based auxin biosensors in synthetic auxin-responsive reporter lines. However, the contributions of auxin biosynthesis and metabolism to the auxin gradient have been largely elusive. Additionally, the available information on subcellular auxin localization is still limited. Here we designed fluorescently labeled auxin analogs that remain active for auxin transport but are inactive for auxin signaling and metabolism. Fluorescent auxin analogs enable the selective visualization of the distribution of auxin by the auxin transport system. Together with auxin biosynthesis inhibitors and an auxin biosensor, these analogs indicated a substantial contribution of local auxin biosynthesis to the formation of auxin maxima at the root apex. Moreover, fluorescent auxin analogs mainly localized to the endoplasmic reticulum in cultured cells and roots, implying the presence of a subcellular auxin gradient in the cells. Our work not only provides a useful tool for the plant chemical biology field but also demonstrates a new strategy for imaging the distribution of small-molecule hormones. PMID:25049419

  3. Detection of Anatoxin-a and Three Analogs in Anabaena spp. Cultures: New Fluorescence Polarization Assay and Toxin Profile by LC-MS/MS

    Directory of Open Access Journals (Sweden)

    Jon A. Sanchez

    2014-01-01

    Full Text Available Anatoxin-a (ATX is a potent neurotoxin produced by several species of Anabaena spp. Cyanobacteria blooms around the world have been increasing in recent years; therefore, it is urgent to develop sensitive techniques that unequivocally confirm the presence of these toxins in fresh water and cyanobacterial samples. In addition, the identification of different ATX analogues is essential to later determine its toxicity. In this paper we designed a fluorescent polarization (FP method to detect ATXs in water samples. A nicotinic acetylcholine receptor (nAChR labeled with a fluorescein derivative was used to develop this assay. Data showed a direct relationship between the amount of toxin in a sample and the changes in the polarization degree of the emitted light by the labeled nAChR, indicating an interaction between the two molecules. This method was used to measure the amount of ATX in three Anabaena spp. cultures. Results indicate that it is a good method to show ATXs presence in algal samples. In order to check the toxin profile of Anabaena cultures a LC-MS/MS method was also developed. Within this new method, ATX-a, retention time (RT 5 min, and three other molecules with a mass m/z 180.1 eluting at 4.14 min, 5.90 min and 7.14 min with MS/MS spectra characteristic of ATX toxin group not previously identified were detected in the Anabaena spp. cultures. These ATX analogues may have an important role in the toxicity of the sample.

  4. Arabinogalactan biosynthesis

    DEFF Research Database (Denmark)

    Poulsen, Christian Peter; Dilokpimol, Adiphol; Geshi, Naomi

    2015-01-01

    Arabinogalactan proteins are abundant cell surface proteoglycans in plants and are implicated to act as developmental markers during plant growth. We previously reported that AtGALT31A, AtGALT29A, and AtGLCAT14A-C, which are involved in the biosynthesis of arabinogalactan proteins, localize......GALT29A. Therefore, the electrostatic status of Y144, which is regulated by an unknown kinase/phosphatase system, may regulate AtGALT29A enzyme activity. Moreover, we have identified additional proteins, apyrase 3 (APY3; At1g14240) and UDPglucuronate epimerases 1 and 6 (GAE1, At4g30440; GAE6, At3g23820...

  5. The role of fluorescence polarization immuno-assay in the diagnosis of plant-induced cardiac glycoside poisoning livestock in South Africa

    Directory of Open Access Journals (Sweden)

    R.A. Schultz

    2005-09-01

    Full Text Available Poisoning with cardiac glycoside-containing plants is collectively the most important plant-associated poisoning of livestock in southern Africa. As a diagnosis of this significant poisoning is currently based on circumstantial evidence, a practical chemical procedure indicating the presence of cardiac glycosides in plants and animal specimens would be of considerable benefit. The fluorescence polarization immunoassay (FPIA method, used to determine digoxin plasma levels in humans and dogs, was adapted to estimate cardiac glycoside levels in known cardiac-glycoside- containing plants as well as in the rumen and organs of dosed sheep. Positive FPIA values were obtained with bufadienolide-containing plants, while negative results were obtained with plants not known to contain cardiac glycosides. The FPIA has aided in the diagnosis of cardiac glycoside poisoning in livestock and game in 30 outbreaks examined at the Division of Toxicology, Onderstepoort Veterinary Institute. Each outbreak is briefly described. As a result of this assay, a better understanding of cardiac glycoside poisoning has been reached.

  6. Studies on the metabolism and toxicological detection of the amphetamine-like anorectic fenproporex in human urine by gas chromatography-mass spectrometry and fluorescence polarization immunoassay.

    Science.gov (United States)

    Kraemer, T; Theis, G A; Weber, A A; Maurer, H H

    2000-01-28

    Studies on the metabolism and the toxicological analysis of fenproporex (R,S-3-[(1-phenyl-2-propyl)-amino]-propionitrile, FP) using GC-MS and fluorescence polarization immunoassay are described. The metabolites were identified in urine samples of volunteers by GC-MS after cleavage of conjugates, extraction and acetylation. Besides unchanged FP, fourteen metabolites, including amphetamine, could be identified. Two partially overlapping metabolic pathways could be postulated: ring degradation by one- and two-fold aromatic hydroxylation followed by methylation and side chain degradation by N-dealkylation to amphetamine (AM). A minor pathway leads via beta-hydroxylation of AM to norephedrine. For GC-MS detection, the systematic toxicological analysis procedure including acid hydrolysis, extraction at pH 8-9 and acetylation was suitable (detection limits 50 ng/ml for FP and 100 ng/ml for AM). Excretion studies showed, that only AM but neither FP nor its specific metabolites were detectable 30-60 h after ingestion of 20 mg of FP. Therefore, misinterpretation can occur. The Abbott TDx FPIA amphetamine/methamphetamine II gave positive results up to 58 h. All the positive immunoassay results could be confirmed by the described GC-MS procedure.

  7. Rapid screening and identification of dominant B cell epitopes of HBV surface antigen by quantum dot-based fluorescence polarization assay

    Science.gov (United States)

    Meng, Zhongji; Song, Ruihua; Chen, Yue; Zhu, Yang; Tian, Yanhui; Li, Ding; Cui, Daxiang

    2013-03-01

    A method for quickly screening and identifying dominant B cell epitopes was developed using hepatitis B virus (HBV) surface antigen as a target. Eleven amino acid fragments from HBV surface antigen were synthesized by 9-fluorenylmethoxy carbonyl solid-phase peptide synthesis strategy, and then CdTe quantum dots were used to label the N-terminals of all peptides. After optimizing the factors for fluorescence polarization (FP) immunoassay, the antigenicities of synthetic peptides were determined by analyzing the recognition and combination of peptides and standard antibody samples. The results of FP assays confirmed that 10 of 11 synthetic peptides have distinct antigenicities. In order to screen dominant antigenic peptides, the FP assays were carried out to investigate the antibodies against the 10 synthetic peptides of HBV surface antigen respectively in 159 samples of anti-HBV surface antigen-positive antiserum. The results showed that 3 of the 10 antigenic peptides may be immunodominant because the antibodies against them existed more widely among the samples and their antibody titers were higher than those of other peptides. Using three dominant antigenic peptides, 293 serum samples were detected for HBV infection by FP assays; the results showed that the antibody-positive ratio was 51.9% and the sensitivity and specificity were 84.3% and 98.2%, respectively. In conclusion, a quantum dot-based FP assay is a very simple, rapid, and convenient method for determining immunodominant antigenic peptides and has great potential in applications such as epitope mapping, vaccine designing, or clinical disease diagnosis in the future.

  8. Investigation of Antigen-Antibody Interactions of Sulfonamides with a Monoclonal Antibody in a Fluorescence Polarization Immunoassay Using 3D-QSAR Models

    Directory of Open Access Journals (Sweden)

    Jianzhong Shen

    2012-05-01

    Full Text Available A three-dimensional quantitative structure-activity relationship (3D-QSAR model of sulfonamide analogs binding a monoclonal antibody (MAbSMR produced against sulfamerazine was carried out by Distance Comparison (DISCOtech, comparative molecular field analysis (CoMFA, and comparative molecular similarity indices analysis (CoMSIA. The affinities of the MAbSMR, expressed as Log10IC50, for 17 sulfonamide analogs were determined by competitive fluorescence polarization immunoassay (FPIA. The results demonstrated that the proposed pharmacophore model containing two hydrogen-bond acceptors, two hydrogen-bond donors and two hydrophobic centers characterized the structural features of the sulfonamides necessary for MAbSMR binding. Removal of two outliers from the initial set of 17 sulfonamide analogs improved the predictability of the models. The 3D-QSAR models of 15 sulfonamides based on CoMFA and CoMSIA resulted in q2cv values of 0.600 and 0.523, and r2 values of 0.995 and 0.994, respectively, which indicates that both methods have significant predictive capability. Connolly surface analysis, which mainly focused on steric force fields, was performed to complement the results from CoMFA and CoMSIA. This novel study combining FPIA with pharmacophore modeling demonstrates that multidisciplinary research is useful for investigating antigen-antibody interactions and also may provide information required for the design of new haptens.

  9. From Dark to Light to Fluorescence Resonance Energy Transfer (FRET): Polarity-Sensitive Aggregation-Induced Emission (AIE)-Active Tetraphenylethene-Fused BODIPY Dyes with a Very Large Pseudo-Stokes Shift.

    Science.gov (United States)

    Şen, Esra; Meral, Kadem; Atılgan, Serdar

    2016-01-11

    The work presented herein is devoted to the fabrication of large Stokes shift dyes in both organic and aqueous media by combining dark resonance energy transfer (DRET) and fluorescence resonance energy transfer (FRET) in one donor-acceptor system. In this respect, a series of donor-acceptor architectures of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes substituted by one, two, or three tetraphenylethene (TPE) luminogens were designed and synthesised. The photophysical properties of these three chromophore systems were studied to provide insight into the nature of donor-acceptor interactions in both THF and aqueous media. Because the generation of emissive TPE donor(s) is strongly polarity dependent, due to its aggregation-induced emission (AIE) feature, one might expect the formation of appreciable fluorescence emission intensity with a very large pseudo-Stokes shift in aqueous media when considering FRET process. Interestingly, similar results were also recorded in THF for the chromophore systems, although the TPE fragment(s) of the dyes are non-emissive. The explanation for this photophysical behaviour lies in the DRET. This is the first report on combining two energy-transfer processes, namely, FRET and DRET, in one polarity-sensitive donor-acceptor pair system. The accuracy of the dark-emissive donor property of the TPE luminogen is also presented for the first time as a new feature for AIE phenomena. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Heidelberg polarized alkali source

    International Nuclear Information System (INIS)

    Kraemer, D.; Steffens, E.; Jaensch, H.; Philipps Universitaet, Marburg, Germany)

    1984-01-01

    A new atomic beam type polarized alkali ion source has been installed at Heidelberg. In order to improve the beam polarization considerably optical pumping is applied in combination with an adiabatic medium field transition which results in beams in single hyperfine sublevels. The m state population is determined by laser-induced fluorescence spectroscopy. Highly polarized beams (P/sub s/ > 0.9, s = z, zz) with intensities of 30 to 130 μA can be extracted for Li + and Na + , respectively

  11. Polarization Optics

    OpenAIRE

    Fressengeas, Nicolas

    2010-01-01

    The physics of polarization optics *Polarized light propagation *Partially polarized light; DEA; After a brief introduction to polarization optics, this lecture reviews the basic formalisms for dealing with it: Jones Calculus for totally polarized light and Stokes parameters associated to Mueller Calculus for partially polarized light.

  12. Chemical genetics to examine cellulose biosynthesis

    Directory of Open Access Journals (Sweden)

    Seth eDebolt

    2013-01-01

    Full Text Available Long-term efforts to decode plant cellulose biosynthesis via molecular genetics and biochemical strategies are being enhanced by the ever-expanding scale of omics technologies. An alternative approach to consider are the prospects for inducing change in plant metabolism using exogenously supplied chemical ligands. Cellulose biosynthesis inhibitors (CBI have been identified among known herbicides, during diverse combinatorial chemical libraries screens, and natural chemical screens from microbial agents. In this review, we summarize the current knowledge of the inhibitory effects of CBIs and further group them by how they influence fluorescently tagged cellulose synthase A (CESA proteins. Additional attention is paid to the continuing development of the CBI toolbox to explore the cell biology and genetic mechanisms underpinning effector molecule activity.

  13. Angle and Polarization Dependent Fluorescence EXAFS Measurements on Al-doped Single Crystal V_2O3 Above and Below the Transition Temperature

    Science.gov (United States)

    Müller, O.; Pfalzer, P.; Schramme, M.; Urbach, J.-P.; Klemm, M.; Horn, S.; Frenkel, A. I.; Denboer, M. L.

    1998-03-01

    We present angle and polarisation dependent flourescence EXAFS measured on Al-doped single crystal V_2O3 below and above the structural phase transition from monoclinic to trigonal. Strong self-absorption distorted the spectra; this was corrected by using the procedure described by Tröger et al. (L. Tröger, D. Arvantis, K. Baberschke, H. Michaelis, U. Grimm, and E. Zschech, Phys. Rev. B,.46), 3238 (1992), generalized to the Lytle detector employed in our work. The spectra show pronounced dependence on the angle between the threefold symmetry axes and the polarization of the incident photons, making it possible to measure the local atomic distances in different directions. We compare our results with the measurements of Frenkel et al. (A. I. Frenkel, E. A. Stern, and F. A. Chudnovsky, Sol. State Comm.102), 637 (1997) on pure V_2O3 They found that locally the monoclinic distortion persists in the trigonal metallic phase.

  14. Biosynthesis of tylophora alkaloids

    International Nuclear Information System (INIS)

    Mulchandani, N.B.; Iyer, S.S.; Badheka, L.P.

    1974-01-01

    Using labelled precursors, biosynthesis of the tylophora alkaloids, tylophorine, tylophorinidine and tylophorinide has been investigated in Tylophora asthmatica plants. The radioactive precursors, phenylalanine-2- 14 C, benzoic acid-1- 14 C, benzoic acid-ring 14 C, acetate-2- 14 C, ornithine-5- 14 C, acetate-2- 14 C, ornithine-5- 14 C and cinnamic acid-2- 14 C were administered to the plants individually by wick technique. Tylophorine was isolated in each case and assayed for its radioactivity to find out the incorporation of the label into it. The results indicate that: (1) phenylalanine via cinnamic acid is an important precursor in the biosynthesis of tylophorine (2) orinithine participates in tylophorine biosynthesis via pyrroline and (3) tylophorinidine may be a direct precursor of tylophorine. (M.G.B.)

  15. Aflatoxin biosynthesis: current frontiers.

    Science.gov (United States)

    Roze, Ludmila V; Hong, Sung-Yong; Linz, John E

    2013-01-01

    Aflatoxins are among the principal mycotoxins that contaminate economically important food and feed crops. Aflatoxin B1 is the most potent naturally occurring carcinogen known and is also an immunosuppressant. Occurrence of aflatoxins in crops has vast economic and human health impacts worldwide. Thus, the study of aflatoxin biosynthesis has become a focal point in attempts to reduce human exposure to aflatoxins. This review highlights recent advances in the field of aflatoxin biosynthesis and explores the functional connection between aflatoxin biosynthesis, endomembrane trafficking, and response to oxidative stress. Dissection of the regulatory mechanisms involves a complete comprehension of the aflatoxin biosynthetic process and the dynamic network of transcription factors that orchestrates coordinated expression of the target genes. Despite advancements in the field, development of a safe and effective multifaceted approach to solve the aflatoxin food contamination problem is still required.

  16. Biosynthesis of Gold Nanoparticles Using Pseudomonas Aeruginosa

    International Nuclear Information System (INIS)

    Abd El-Aziz, M.; Badr, Y.; Mahmoud, M. A.

    2007-01-01

    Pseudomonas aeruginosa were used for extracellular biosynthesis of gold nanoparticles (Au NPs). Consequently, Au NPs were formed due to reduction of gold ion by bacterial cell supernatant of P. aeruginos ATCC 90271, P. aeruginos (2) and P. aeruginos (1). The UV-Vis. and fluorescence spectra of the bacterial as well as chemical prepared Au NPs were recorded. Transmission electron microscopy (TEM) micrograph showed the formation of well-dispersed gold nanoparticles in the range of 15-30 nm. The process of reduction being extracellular and may lead to the development of an easy bioprocess for synthesis of Au NPs

  17. Rough lipopolysaccharide of Brucella abortus RB51 as a common antigen for serological detection of B. ovis, B. canis, and B. abortus RB51 exposure using indirect enzyme immunoassay and fluorescence polarization assay.

    Science.gov (United States)

    Nielsen, K; Smith, P; Conde, S; Draghi de Benitez, G; Gall, D; Halbert, G; Kenny, K; Massengill, C; Muenks, Q; Rojas, X; Perez, B; Samartino, L; Silva, P; Tollersrud, T; Jolley, M

    2004-01-01

    Rough lipopolysaccharide (RLPS) antigens were prepared from cultures of Brucella abortus RB51, B. ovis, and B. canis. The preparations were standardized by weight and tested with sera from cattle immunized with B. abortus RB51, sheep infected with B. ovis, and dogs infected with B. canis. Populations of unexposed animals of each species were also tested. The tests used were the indirect enzyme immunoassay (IELISA) using RLPS and the fluorescence polarization assay (FPA) using RLPS core fractions, labeled with fluorescein isothiocyanate. The IELISA using B. abortus RB51 RLPS antigen resulted in sensitivity and specificity values of 94.8% and 97.3%, respectively, when testing bovine sera, 98.5% and 97.8% when testing ovine sera, and 95.8% and 100% when testing dog sera. The IELISA using B. ovis RLPS antigen gave sensitivity and specificity values of 80.5% and 91.7%, respectively with bovine sera, 98.9% and 93.8% with sheep sera, and 70.8% and 79.8% with dog sera. The IELISA using B. canis RLPS antigen resulted in sensitivity and specificity values of 97.0% and 97.4%, respectively, with bovine sera, 96.2% and 96.3% with sheep sera, and 95.8% and 98.8% with dog sera. Labeling RLPS core from B. ovis and B. canis with fluorescein was not successful. B. abortus RB51 core labeled with fluorescein resulted in sensitivity and specificity values of 93.5% and 99.8%, respectively, with bovine sera and 78.1% and 99.0% with sheep sera. It was not possible to test the dog sera in the FPA.

  18. Fluorescence spectroscopy

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2016-01-01

    Fluorescence spectroscopy is a powerful experimental tool used by scientists from many disciplines. During the last decades there have been important developments on distinct fluorescence methods, particularly those related to the study of biological phenomena. This chapter discusses the foundati......Fluorescence spectroscopy is a powerful experimental tool used by scientists from many disciplines. During the last decades there have been important developments on distinct fluorescence methods, particularly those related to the study of biological phenomena. This chapter discusses...

  19. [Optimization of oxytetracycline biosynthesis].

    Science.gov (United States)

    Maksimova, E A; Falkov, N N; Izmaĭlov, N N; Romanchuk, N N

    1988-06-01

    It was shown that rising of temperature up to 30 degrees C at the stage of the oxytetracycline-producing organism growth promoted acceleration of the culture growth rate and increasing of the antibiotic concentration by the 114th hour of the biosynthetic process. For the apparatus used in the study optimal aeration and agitation conditions were developed. To provide optimal parameters during biosynthesis of oxytetracycline, it was recommended to use the aeration rate of 1 v/v.min and the specific mechanical power for mixing of not less than 1 kW/m3.

  20. Biosynthesis of Rishirilide B

    Directory of Open Access Journals (Sweden)

    Philipp Schwarzer

    2018-03-01

    Full Text Available Rishirilide B was isolated from Streptomyces rishiriensis and Streptomyces bottropensis on the basis of its inhibitory activity towards alpha-2-macroglobulin. The biosynthesis of rishirilide B was investigated by feeding experiments with different 13C labelled precursors using the heterologous host Streptomyces albus J1074::cos4 containing a cosmid encoding of the gene cluster responsible for rishirilide B production. NMR spectroscopic analysis of labelled compounds demonstrate that the tricyclic backbone of rishirilide B is a polyketide synthesized from nine acetate units. One of the acetate units is decarboxylated to give a methyl group. The origin of the starter unit was determined to be isobutyrate.

  1. (+)-Germacrene A Biosynthesis

    Science.gov (United States)

    de Kraker, Jan-Willem; Franssen, Maurice C.R.; de Groot, Aede; König, Wilfried A.; Bouwmeester, Harro J.

    1998-01-01

    The leaves and especially the roots of chicory (Cichorium intybus L.) contain high concentrations of bitter sesquiterpene lactones such as the guianolides lactupicrin, lactucin, and 8-deoxylactucin. Eudesmanolides and germacranolides are present in smaller amounts. Their postulated biosynthesis through the mevalonate-farnesyl diphosphate-germacradiene pathway has now been confirmed by the isolation of a (+)-germacrene A synthase from chicory roots. This sesquiterpene cyclase was purified 200-fold using a combination of anion-exchange and dye-ligand chromatography. It has a Km value of 6.6 μm, an estimated molecular mass of 54 kD, and a (broad) pH optimum around 6.7. Germacrene A, the enzymatic product, proved to be much more stable than reported in literature. Its heat-induced Cope rearrangement into (−)-β-elemene was utilized to determine its absolute configuration on an enantioselective gas chromatography column. To our knowledge, until now in sesquiterpene biosynthesis, germacrene A has only been reported as an (postulated) enzyme-bound intermediate, which, instead of being released, is subjected to additional cyclization(s) by the same enzyme that generated it from farnesyl diphosphate. However, in chicory germacrene A is released from the sesquiterpene cyclase. Apparently, subsequent oxidations and/or glucosylation of the germacrane skeleton, together with a germacrene cyclase, determine whether guaiane- or eudesmane-type sesquiterpene lactones are produced. PMID:9701594

  2. Polarization developments

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist

  3. Polarization, political

    NARCIS (Netherlands)

    Wojcieszak, M.; Mazzoleni, G.; Barnhurst, K.G.; Ikeda, K.; Maia, R.C.M.; Wessler, H.

    2015-01-01

    Polarization has been studied in three different forms: on a social, group, and individual level. This entry first focuses on the undisputed phenomenon of elite polarization (i.e., increasing adherence of policy positions among the elites) and also outlines different approaches to assessing mass

  4. Polarization holography

    DEFF Research Database (Denmark)

    Nikolova, L.; Ramanujam, P.S.

    Current research into holography is concerned with applications in optically storing, retrieving, and processing information. Polarization holography has many unique properties compared to conventional holography. It gives results in high efficiency, achromaticity, and special polarization...... properties. This books reviews the research carried out in this field over the last 15 years. The authors provide basic concepts in polarization and the propagation of light through anisotropic materials, before presenting a sound theoretical basis for polarization holography. The fabrication...... and characterization of azobenzene based materials, which remain the most efficient for the purpose, is described in detail. This is followed by a description of other materials that are used in polarization holography. An in-depth description of various applications, including display holography and optical storage...

  5. Polar Bears

    Science.gov (United States)

    Amstrup, Steven C.; Douglas, David C.; Reynolds, Patricia E.; Rhode, E.B.

    2002-01-01

    Polar bears (Ursus maritimus) are hunted throughout most of their range. In addition to hunting polar bears of the Beaufort Sea region are exposed to mineral and petroleum extraction and related human activities such as shipping road-building, and seismic testing (Stirling 1990).Little was known at the start of this project about how polar bears move about in their environment, and although it was understood that many bears travel across political borders, the boundaries of populations had not been delineated (Amstrup 1986, Amstrup et al. 1986, Amstrup and DeMaster 1988, Garner et al. 1994, Amstrup 1995, Amstrup et al. 1995, Amstrup 2000).As human populations increase and demands for polar bears and other arctic resources escalate, managers must know the sizes and distributions of the polar bear populations. Resource managers also need reliable estimates of breeding rates, reproductive intervals, litter sizes, and survival of young and adults.Our objectives for this research were 1) to determine the seasonal and annual movements of polar bears in the Beaufort Sea, 2) to define the boundaries of the population(s) using this region, 3) to determine the size and status of the Beaufort Sea polar bear population, and 4) to establish reproduction and survival rates (Amstrup 2000).

  6. Nine New Fluorescent Probes

    Science.gov (United States)

    Lin, Tsung-I.; Jovanovic, Misa V.; Dowben, Robert M.

    1989-06-01

    Absorption and fluorescence spectroscopic studies are reported here for nine new fluorescent probes recently synthesized in our laboratories: four pyrene derivatives with substituents of (i) 1,3-diacetoxy-6,8-dichlorosulfonyl, (ii) 1,3-dihydroxy-6,8-disodiumsulfonate, (iii) 1,3-disodiumsulfonate, and (iv) l-ethoxy-3,6,8-trisodiumsulfonate groups, and five [7-julolidino] coumarin derivatives with substituents of (v) 3-carboxylate-4-methyl, (vi) 3- methylcarboxylate, (vii) 3-acetate-4-methyl, (viii) 3-propionate-4-methyl, and (ix) 3-sulfonate-4-methyl groups. Pyrene compounds i and ii and coumarin compounds v and vi exhibit interesting absorbance and fluorescence properties: their absorption maxima are red shifted compared to the parent compound to the blue-green region, and the band width broadens considerably. All four blue-absorbing dyes fluoresce intensely in the green region, and the two pyrene compounds emit at such long wavelengths without formation of excimers. The fluorescence properties of these compounds are quite environment-sensitive: considerable spectral shifts and fluorescence intensity changes have been observed in the pH range from 3 to 10 and in a wide variety of polar and hydrophobic solvents with vastly different dielectric constants. The high extinction and fluorescence quantum yield of these probes make them ideal fluorescent labeling reagents for proteins, antibodies, nucleic acids, and cellular organelles. The pH and hydrophobicity-dependent fluorescence changes can be utilized as optical pH and/or hydrophobicity indicators for mapping environmental difference in various cellular components in a single cell. Since all nine probes absorb in the UV, but emit at different wavelengths in the visible, these two groups of compounds offer an advantage of utilizing a single monochromatic light source (e.g., a nitrogen laser) to achieve multi-wavelength detection for flow cytometry application. As a first step to explore potential application in

  7. Serine biosynthesis and transport defects.

    Science.gov (United States)

    El-Hattab, Ayman W

    2016-07-01

    l-serine is a non-essential amino acid that is biosynthesized via the enzymes phosphoglycerate dehydrogenase (PGDH), phosphoserine aminotransferase (PSAT), and phosphoserine phosphatase (PSP). Besides its role in protein synthesis, l-serine is a potent neurotrophic factor and a precursor of a number of essential compounds including phosphatidylserine, sphingomyelin, glycine, and d-serine. Serine biosynthesis defects result from impairments of PGDH, PSAT, or PSP leading to systemic serine deficiency. Serine biosynthesis defects present in a broad phenotypic spectrum that includes, at the severe end, Neu-Laxova syndrome, a lethal multiple congenital anomaly disease, intermediately, infantile serine biosynthesis defects with severe neurological manifestations and growth deficiency, and at the mild end, the childhood disease with intellectual disability. A serine transport defect resulting from deficiency of the ASCT1, the main transporter for serine in the central nervous system, has been recently described in children with neurological manifestations that overlap with those observed in serine biosynthesis defects. l-serine therapy may be beneficial in preventing or ameliorating symptoms in serine biosynthesis and transport defects, if started before neurological damage occurs. Herein, we review serine metabolism and transport, the clinical, biochemical, and molecular aspects of serine biosynthesis and transport defects, the mechanisms of these diseases, and the potential role of serine therapy. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Carotenoid Biosynthesis in Fusarium

    Directory of Open Access Journals (Sweden)

    Javier Avalos

    2017-07-01

    Full Text Available Many fungi of the genus Fusarium stand out for the complexity of their secondary metabolism. Individual species may differ in their metabolic capacities, but they usually share the ability to synthesize carotenoids, a family of hydrophobic terpenoid pigments widely distributed in nature. Early studies on carotenoid biosynthesis in Fusarium aquaeductuum have been recently extended in Fusarium fujikuroi and Fusarium oxysporum, well-known biotechnological and phytopathogenic models, respectively. The major Fusarium carotenoid is neurosporaxanthin, a carboxylic xanthophyll synthesized from geranylgeranyl pyrophosphate through the activity of four enzymes, encoded by the genes carRA, carB, carT and carD. These fungi produce also minor amounts of β-carotene, which may be cleaved by the CarX oxygenase to produce retinal, the rhodopsin’s chromophore. The genes needed to produce retinal are organized in a gene cluster with a rhodopsin gene, while other carotenoid genes are not linked. In the investigated Fusarium species, the synthesis of carotenoids is induced by light through the transcriptional induction of the structural genes. In some species, deep-pigmented mutants with up-regulated expression of these genes are affected in the regulatory gene carS. The molecular mechanisms underlying the control by light and by the CarS protein are currently under investigation.

  9. Biosynthesis of Tetrahydroisoquinoline Antibiotics.

    Science.gov (United States)

    Tang, Gong-Li; Tang, Man-Cheng; Song, Li-Qiang; Zhang, Yue

    2016-01-01

    The tetrahydroisoquinoline (THIQ) alkaloids are naturally occurring antibiotics isolated from a variety of microorganisms and marine invertebrates. This family of natural products exhibit broad spectrum antimicrobial and strong antitumor activities, and the potency of clinical application has been validated by the marketing of ecteinascidin 743 (ET-743) as anticancer drug. In the past 20 years, the biosynthetic gene cluster of six THIQ antibiotics has been characterized including saframycin Mx1 from Myxococcus xanthus, safracin-B from Pseudomonas fluorescens, saframycin A, naphthyridinomycin, and quinocarcin from Streptomyces, as well as ET-743 from Ecteinascidia turbinata. This review gives a brief summary of the current status in understanding the molecular logic for the biosynthesis of these natural products, which provides new insights on the biosynthetic machinery involved in the nonribosomal peptide synthetase system. The proposal of the THIQ biosynthetic pathway not only shows nature's route to generate such complex molecules, but also set the stage to develop a different process for production of ET-743 by synthetic biology.

  10. Stereoselectivity in Polyphenol Biosynthesis

    Science.gov (United States)

    Lewis, Norman G.; Davin, Laurence B.

    1992-01-01

    Stereoselectivity plays an important role in the late stages of phenyl-propanoid metabolism, affording lignins, lignans, and neolignans. Stereoselectivity is manifested during monolignol (glucoside) synthesis, e.g., where the geometry (E or Z) of the pendant double bond affects the specificity of UDPG:coniferyl alcohol glucosyltransferases in different species. Such findings are viewed to have important ramifications in monolignol transport and storage processes, with roles for both E- and Z-monolignols and their glucosides in lignin/lignan biosynthesis being envisaged. Stereoselectivity is also of great importance in enantiose-lective enzymatic processes affording optically active lignans. Thus, cell-free extracts from Forsythia species were demonstrated to synthesize the enantiomerically pure lignans, (-)-secoisolariciresinol, and (-)-pinoresinol, when NAD(P)H, H2O2 and E-coniferyl alcohol were added. Progress toward elucidating the enzymatic steps involved in such highly stereoselective processes is discussed. Also described are preliminary studies aimed at developing methodologies to determine the subcellular location of late-stage phenylpropanoid metabolites (e.g., coniferyl alcohol) and key enzymes thereof, in intact tissue or cells. This knowledge is essential if questions regarding lignin and lignan tissue specificity and regulation of these processes are to be deciphered.

  11. Glycolipid biosynthesis in cyanobacteria

    International Nuclear Information System (INIS)

    Van Dusen, W.J.; Jaworski, J.G.

    1987-01-01

    The biosynthesis of monogalactosyldiacyl-glycerol (MGDG) was studied in five different cyanobacteria. Previous work has shown Anabaena variabilis to synthesize both MGDG and monoglucosyl-diacylglycerol (MG1cDG) with MG1cDG being the precursor of MGDG. They have examined four other cyanobacteria to determine if a similar relationship exists. The cyanobacteria studied were Anabaena variabilis, Chlorogloeopsis sp., Schizothrix calcicola, Anacystis nidulans, and Anacystis marina. Each were grown in liquid culture and lipids were labeled with 14 C]CO 2 for 20 min., 1.0 hr, 1.0 hr + 10 hr chase. Glycolipids were analyzed by initial separation of MGDG and MG1cDG by TLC followed by further analysis by HPLC. Complete separation of molecular species was obtained isocratically on an ODS column. All of the cyanobacteria labeled 16-C and 18-C fatty acids except for A. marina which labeled only 14-C and 16-C fatty acids. Desaturation of the fatty acids could be observed in the 1.0 hr and chase experiments. All were capable of labeling both MG1cDG and MGDG with the precursor-product relationship being observed. There does not appear to be a direct relationship between the epimerization of the sugar moiety and fatty acid desaturation

  12. Biosynthesis of silver nanoparticles.

    Science.gov (United States)

    Poulose, Subin; Panda, Tapobrata; Nair, Praseetha P; Théodore, Thomas

    2014-02-01

    Metal nanoparticles have unique optical, electronic, and catalytic properties. There exist well-defined physical and chemical processes for their preparation. Those processes often yield small quantities of nanoparticles having undesired morphology, and involve high temperatures for the reaction and the use of hazardous chemicals. Relatively, the older technique of bioremediation of metals uses either microorganisms or their components for the production of nanoparticles. The nanoparticles obtained from bacteria, fungi, algae, plants and their components, etc. appear environment-friendly, as toxic chemicals are not used in the processes. In addition to this, the formation of nanoparticles takes place at almost normal temperature and pressure. Control of the shape and size of the nanoparticles is possible by appropriate selection of the pH and temperature. Three important steps are the bioconversion of Ag+ ions, conversion of desired crystals to nanoparticles, and nanoparticle stability. Generally, nanoparticles are characterized by the UV-visible spectroscopy and use of the electron microscope. Silver nanoparticles are used as antimicrobial agents and they possess antifungal, anti-inflammatory, and anti-angiogenic properties. This review highlights the biosynthesis of silver nanoparticles by various organisms, possible mechanisms of their synthesis, their characterization, and applications of silver nanoparticles.

  13. Fluorescence anisotropy measurements in solution: Methods and reference materials (IUPAC Technical Report)

    OpenAIRE

    AMELOOT, Marcel; Van de Ven, Martin; Ulises Acuna, A.; Valeur, Bernard

    2013-01-01

    After recalling the basic relations relevant to both steady-state and time-resolved fluorescence polarization, it is shown how the values of steady-state polarized intensities recorded experimentally usually need to be corrected for systematic effects and errors, caused by instrumentation and sample properties. A list of selected reference values of steady-state fluorescence anisotropy and polarization is given. Attention is also paid to analysis of time-resolved fluorescence anisotropy data ...

  14. Auxin biosynthesis and storage forms

    Science.gov (United States)

    Strader, Lucia C.

    2013-01-01

    The plant hormone auxin drives plant growth and morphogenesis. The levels and distribution of the active auxin indole-3-acetic acid (IAA) are tightly controlled through synthesis, inactivation, and transport. Many auxin precursors and modified auxin forms, used to regulate auxin homeostasis, have been identified; however, very little is known about the integration of multiple auxin biosynthesis and inactivation pathways. This review discusses the many ways auxin levels are regulated through biosynthesis, storage forms, and inactivation, and the potential roles modified auxins play in regulating the bioactive pool of auxin to affect plant growth and development. PMID:23580748

  15. Hypericin: chemical synthesis and biosynthesis.

    Science.gov (United States)

    Huang, Lin-Fang; Wang, Zeng-Hui; Chen, Shi-Lin

    2014-02-01

    Hypericin is one of the most important phenanthoperylene quinones extracted mainly from plants of the genus Hypericum belonging to the sections Euhypericum and Campylosporus of Keller's classification. Widespread attention to the antiviral and anti-tumor properties of hypericin has spurred investigations of the chemical synthesis and biosynthesis of this unique compound. However, the synthetic strategies are challenging for organic and biological chemists. In this review, specific significant advances in total synthesis, semi-synthesis, and biosynthesis in the past decades are summarized. Copyright © 2014 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

  16. Political polarization

    OpenAIRE

    Dixit, Avinash K.; Weibull, Jörgen W.

    2007-01-01

    Failures of government policies often provoke opposite reactions from citizens; some call for a reversal of the policy, whereas others favor its continuation in stronger form. We offer an explanation of such polarization, based on a natural bimodality of preferences in political and economic contexts and consistent with Bayesian rationality.

  17. Political polarization.

    Science.gov (United States)

    Dixit, Avinash K; Weibull, Jörgen W

    2007-05-01

    Failures of government policies often provoke opposite reactions from citizens; some call for a reversal of the policy, whereas others favor its continuation in stronger form. We offer an explanation of such polarization, based on a natural bimodality of preferences in political and economic contexts and consistent with Bayesian rationality.

  18. An optically pumped polarized lithium ion source

    International Nuclear Information System (INIS)

    Myers, E.G.; Mendez, A.J.; Schmidt, B.G.; Kemper, K.W.

    1991-01-01

    A laser-optically-pumped polarized lithium ion source is being developed to provide beams of nuclear polarized 6,7 Li - for injection into the FSU tandem Van de Graaff-linac. Electro-optically modulated, circularly polarized light optically pumps a lithium atomic beam into a single magnetic substate, M 1 =1, M J =1/2. No inhomogeneous magnetic field (sextupole or quadrupole) is needed. Adiabatic rf transitions enable the polarization to be changed by transferring the population into different magnetic substates. Using a second electro-optic to modulate a second beam from the same laser, and Zeeman tuning, the polarization of the atomic beam is obtained by laser induced fluorescence. The polarized atomic beam is ionized to Li + and then charge exchanged to Li - . (orig.)

  19. (vitamin B1) biosynthesis genes

    African Journals Online (AJOL)

    In this study, the gene transcripts of first two enzymes in thiamine biosynthesis pathway, THIC and THI1/THI4 were identified and amplified from oil palm tissues. Primers were designed based on sequence comparison of the genes from Arabidopsis thaliana, Zea mays, Oryza sativa and Alnus glutinosa. Oil palm's responses ...

  20. (-)-Menthol biosynthesis and molecular genetics

    Science.gov (United States)

    Croteau, Rodney B.; Davis, Edward M.; Ringer, Kerry L.; Wildung, Mark R.

    2005-12-01

    (-)-Menthol is the most familiar of the monoterpenes as both a pure natural product and as the principal and characteristic constituent of the essential oil of peppermint ( Mentha x piperita). In this paper, we review the biosynthesis and molecular genetics of (-)-menthol production in peppermint. In Mentha species, essential oil biosynthesis and storage is restricted to the peltate glandular trichomes (oil glands) on the aerial surfaces of the plant. A mechanical method for the isolation of metabolically functional oil glands, has provided a system for precursor feeding studies to elucidate pathway steps, as well as a highly enriched source of the relevant biosynthetic enzymes and of their corresponding transcripts with which cDNA libraries have been constructed to permit cloning and characterization of key structural genes. The biosynthesis of (-)-menthol from primary metabolism requires eight enzymatic steps, and involves the formation and subsequent cyclization of the universal monoterpene precursor geranyl diphosphate to the parent olefin (-)-(4 S)-limonene as the first committed reaction of the sequence. Following hydroxylation at C3, a series of four redox transformations and an isomerization occur in a general “allylic oxidation-conjugate reduction” scheme that installs three chiral centers on the substituted cyclohexanoid ring to yield (-)-(1 R, 3 R, 4 S)-menthol. The properties of each enzyme and gene of menthol biosynthesis are described, as are their probable evolutionary origins in primary metabolism. The organization of menthol biosynthesis is complex in involving four subcellular compartments, and regulation of the pathway appears to reside largely at the level of gene expression. Genetic engineering to up-regulate a flux-limiting step and down-regulate a side route reaction has led to improvement in the composition and yield of peppermint oil.

  1. Study of ciclosporine blood levels in patients after kidney or bone-marrow transplantation. Comparison between the two methods, fluorescence polarization immunoassay and radioimmunoassay. Etude de la ciclosporinemie de patients traites apres greffe de rein ou de moelle. Comparaison entre les methodes par immunofluorescence et radio-immunologique

    Energy Technology Data Exchange (ETDEWEB)

    Sadeg, N.; Pham Huy, C.; Claude, J.R. (Paris-5 Univ., 75 (FR)); Postaire, M.; Lebrec, H.; Hamon, M. (Paris-11 Univ., 92 - Chatenay-Malabry (FR) Hopital Necker-Enfants Malades, 75 - Paris (FR)); Broyer, M.; Gagnadoux, M.F.; Fischer, A. (Hopital Necker-Enfants Malades, 75 - Paris (FR))

    1989-01-01

    The apparition of ciclosporine, immunodepressive drug, has largely improved the organ transplantations. However, the range of blood concentrations must be defined to allow the efficacity of ciclosporine therapy and to avoid toxic reactions, because there are very important variations for a same dosage according to the individuals and the diseases. Relative to the low concentrations to be determined (about one hundred ng/ml), the most useful methods for ciclosporine measurement are based on immunochemical assays. This work compares the two methods: radioimmunoassay (RIA) and fluorescence polarization immunoassay (FPIA) simultaneously performed on several hundred samples. A very significant correlation exists between the two techniques (r = 0.80). The advantages of immunofluorescent assay consists in rapidity, sensibility and facility to realize emergency analysis.

  2. Co-Compartmentation of Terpene Biosynthesis and Storage via Synthetic Droplet

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Cheng [Texas; amp,M Agrilife Synthetic and Systems Biology Innovation Hub, Texas A& amp,M University, College Station, Texas 77843, United States; Department; amp,M University, College Station, Texas 77843, United States; Institute; amp,M University, College Station, Texas 77843, United States; Kim, YongKyoung [Texas; amp,M Agrilife Synthetic and Systems Biology Innovation Hub, Texas A& amp,M University, College Station, Texas 77843, United States; Department; amp,M University, College Station, Texas 77843, United States; Institute; amp,M University, College Station, Texas 77843, United States; Zeng, Yining [Biosciences; Li, Man [Texas; amp,M Agrilife Synthetic and Systems Biology Innovation Hub, Texas A& amp,M University, College Station, Texas 77843, United States; Department; amp,M University, College Station, Texas 77843, United States; Institute; amp,M University, College Station, Texas 77843, United States; Wang, Xin [Texas; amp,M Agrilife Synthetic and Systems Biology Innovation Hub, Texas A& amp,M University, College Station, Texas 77843, United States; Department; amp,M University, College Station, Texas 77843, United States; Institute; amp,M University, College Station, Texas 77843, United States; Hu, Cheng [Texas; amp,M Agrilife Synthetic and Systems Biology Innovation Hub, Texas A& amp,M University, College Station, Texas 77843, United States; Department; amp,M University, College Station, Texas 77843, United States; Institute; amp,M University, College Station, Texas 77843, United States; Gorman, Connor [Texas; amp,M Agrilife Synthetic and Systems Biology Innovation Hub, Texas A& amp,M University, College Station, Texas 77843, United States; Department; amp,M University, College Station, Texas 77843, United States; Institute; amp,M University, College Station, Texas 77843, United States; Dai, Susie Y. [State; Ding, Shi-You [Department; Yuan, Joshua S. [Texas; amp,M Agrilife Synthetic and Systems Biology Innovation Hub, Texas A& amp,M University, College Station, Texas 77843, United States; Department; amp,M University, College Station, Texas 77843, United States; Institute; amp,M University, College Station, Texas 77843, United States

    2018-02-16

    Traditional bioproduct engineering focuses on pathway optimization, yet is often complicated by product inhibition, downstream consumption, and the toxicity of certain products. Here, we present the co-compartmentation of biosynthesis and storage via a synthetic droplet as an effective new strategy to improve the bioproduct yield, with squalene as a model compound. A hydrophobic protein was designed and introduced into the tobacco chloroplast to generate a synthetic droplet for terpene storage. Simultaneously, squalene biosynthesis enzymes were introduced to chloroplasts together with the droplet-forming protein to co-compartmentalize the biosynthesis and storage of squalene. The strategy has enabled a record yield of squalene at 2.6 mg/g fresh weight without compromising plant growth. Confocal fluorescent microscopy imaging, stimulated Raman scattering microscopy, and droplet composition analysis confirmed the formation of synthetic storage droplet in chloroplast. The co-compartmentation of synthetic storage droplet with a targeted metabolic pathway engineering represents a new strategy for enhancing bioproduct yield.

  3. Strategic Polarization.

    Science.gov (United States)

    Kalai, Adam; Kalai, Ehud

    2001-08-01

    In joint decision making, similarly minded people may take opposite positions. Consider the example of a marriage in which one spouse gives generously to charity while the other donates nothing. Such "polarization" may misrepresent what is, in actuality, a small discrepancy in preferences. It may be that the donating spouse would like to see 10% of their combined income go to charity each year, while the apparently frugal spouse would like to see 8% donated. A simple game-theoretic analysis suggests that the spouses will end up donating 10% and 0%, respectively. By generalizing this argument to a larger class of games, we provide strategic justification for polarization in many situations such as debates, shared living accommodations, and disciplining children. In some of these examples, an arbitrarily small disagreement in preferences leads to an arbitrarily large loss in utility for all participants. Such small disagreements may also destabilize what, from game-theoretic point of view, is a very stable equilibrium. Copyright 2001 Academic Press.

  4. Plasmonics Enhanced Smartphone Fluorescence Microscopy

    KAUST Repository

    Wei, Qingshan

    2017-05-12

    Smartphone fluorescence microscopy has various applications in point-of-care (POC) testing and diagnostics, ranging from e.g., quantification of immunoassays, detection of microorganisms, to sensing of viruses. An important need in smartphone-based microscopy and sensing techniques is to improve the detection sensitivity to enable quantification of extremely low concentrations of target molecules. Here, we demonstrate a general strategy to enhance the detection sensitivity of a smartphone-based fluorescence microscope by using surface-enhanced fluorescence (SEF) created by a thin metal-film. In this plasmonic design, the samples are placed on a silver-coated glass slide with a thin spacer, and excited by a laser-diode from the backside through a glass hemisphere, generating surface plasmon polaritons. We optimized this mobile SEF system by tuning the metal-film thickness, spacer distance, excitation angle and polarization, and achieved ~10-fold enhancement in fluorescence intensity compared to a bare glass substrate, which enabled us to image single fluorescent particles as small as 50 nm in diameter and single quantum-dots. Furthermore, we quantified the detection limit of this platform by using DNA origami-based brightness standards, demonstrating that ~80 fluorophores per diffraction-limited spot can be readily detected by our mobile microscope, which opens up new opportunities for POC diagnostics and sensing applications in resource-limited-settings.

  5. Polarized spectral features of human breast tissues through wavelet ...

    Indian Academy of Sciences (India)

    Abstract. Fluorescence characteristics of human breast tissues are investigated through wavelet transform and principal component analysis (PCA). Wavelet transform of polar- ized fluorescence spectra of human breast tissues is found to localize spectral features that can reliably differentiate different tissue types.

  6. Polarized spectral features of human breast tissues through wavelet ...

    Indian Academy of Sciences (India)

    Fluorescence characteristics of human breast tissues are investigated through wavelet transform and principal component analysis (PCA). Wavelet transform of polarized fluorescence spectra of human breast tissues is found to localize spectral features that can reliably differentiate different tissue types. The emission range ...

  7. Vitamin B biosynthesis in plants.

    Science.gov (United States)

    Roje, Sanja

    2007-07-01

    The vitamin B complex comprises water-soluble enzyme cofactors and their derivatives that are essential contributors to diverse metabolic processes in plants as well as in animals and microorganisms. Seven vitamins form this complex: B1 (thiamin (1)), B2 (riboflavin (2)), B3 (niacin (3)), B5 (pantothenic acid (4)), B6 (pyridoxine, pyridoxal (5), and pyridoxamine), B8 (biotin (6)), and B9 (folate (7)). All seven B vitamins are required in the human diet for proper nutrition because humans lack enzymes to synthesize these compounds de novo. This review aims to summarize the present knowledge of vitamin B biosynthesis in plants.

  8. Precessing deuteron polarization

    International Nuclear Information System (INIS)

    Sitnik, I.M.; Volkov, V.I.; Kirillov, D.A.; Piskunov, N.M.; Plis, Yu.A.

    2002-01-01

    The feasibility of the acceleration in the Nuclotron of deuterons polarized in the horizontal plane is considered. This horizontal polarization is named precessing polarization. The effects of the main magnetic field and synchrotron oscillations are included. The precessing polarization is supposed to be used in studying the polarization parameters of the elastic dp back-scattering and other experiments

  9. Light Remodels Lipid Biosynthesis in Nannochloropsis gaditana by Modulating Carbon Partitioning between Organelles.

    Science.gov (United States)

    Alboresi, Alessandro; Perin, Giorgio; Vitulo, Nicola; Diretto, Gianfranco; Block, Maryse; Jouhet, Juliette; Meneghesso, Andrea; Valle, Giorgio; Giuliano, Giovanni; Maréchal, Eric; Morosinotto, Tomas

    2016-08-01

    The seawater microalga Nannochloropsis gaditana is capable of accumulating a large fraction of reduced carbon as lipids. To clarify the molecular bases of this metabolic feature, we investigated light-driven lipid biosynthesis in Nannochloropsis gaditana cultures combining the analysis of photosynthetic functionality with transcriptomic, lipidomic and metabolomic approaches. Light-dependent alterations are observed in amino acid, isoprenoid, nucleic acid, and vitamin biosynthesis, suggesting a deep remodeling in the microalgal metabolism triggered by photoadaptation. In particular, high light intensity is shown to affect lipid biosynthesis, inducing the accumulation of diacylglyceryl-N,N,N-trimethylhomo-Ser and triacylglycerols, together with the up-regulation of genes involved in their biosynthesis. Chloroplast polar lipids are instead decreased. This situation correlates with the induction of genes coding for a putative cytosolic fatty acid synthase of type 1 (FAS1) and polyketide synthase (PKS) and the down-regulation of the chloroplast fatty acid synthase of type 2 (FAS2). Lipid accumulation is accompanied by the regulation of triose phosphate/inorganic phosphate transport across the chloroplast membranes, tuning the carbon metabolic allocation between cell compartments, favoring the cytoplasm, mitochondrion, and endoplasmic reticulum at the expense of the chloroplast. These results highlight the high flexibility of lipid biosynthesis in N. gaditana and lay the foundations for a hypothetical mechanism of regulation of primary carbon partitioning by controlling metabolite allocation at the subcellular level. © 2016 American Society of Plant Biologists. All Rights Reserved.

  10. Light Remodels Lipid Biosynthesis in Nannochloropsis gaditana by Modulating Carbon Partitioning between Organelles1[OPEN

    Science.gov (United States)

    Vitulo, Nicola; Diretto, Gianfranco; Block, Maryse; Jouhet, Juliette; Meneghesso, Andrea; Valle, Giorgio; Giuliano, Giovanni; Maréchal, Eric

    2016-01-01

    The seawater microalga Nannochloropsis gaditana is capable of accumulating a large fraction of reduced carbon as lipids. To clarify the molecular bases of this metabolic feature, we investigated light-driven lipid biosynthesis in Nannochloropsis gaditana cultures combining the analysis of photosynthetic functionality with transcriptomic, lipidomic and metabolomic approaches. Light-dependent alterations are observed in amino acid, isoprenoid, nucleic acid, and vitamin biosynthesis, suggesting a deep remodeling in the microalgal metabolism triggered by photoadaptation. In particular, high light intensity is shown to affect lipid biosynthesis, inducing the accumulation of diacylglyceryl-N,N,N-trimethylhomo-Ser and triacylglycerols, together with the up-regulation of genes involved in their biosynthesis. Chloroplast polar lipids are instead decreased. This situation correlates with the induction of genes coding for a putative cytosolic fatty acid synthase of type 1 (FAS1) and polyketide synthase (PKS) and the down-regulation of the chloroplast fatty acid synthase of type 2 (FAS2). Lipid accumulation is accompanied by the regulation of triose phosphate/inorganic phosphate transport across the chloroplast membranes, tuning the carbon metabolic allocation between cell compartments, favoring the cytoplasm, mitochondrion, and endoplasmic reticulum at the expense of the chloroplast. These results highlight the high flexibility of lipid biosynthesis in N. gaditana and lay the foundations for a hypothetical mechanism of regulation of primary carbon partitioning by controlling metabolite allocation at the subcellular level. PMID:27325666

  11. Polare maskuliniteter

    Directory of Open Access Journals (Sweden)

    Marit Anne Hauan

    2012-05-01

    Full Text Available In this paper my aim is to read and understand the journal of Gerrit de Veer from the last journey of William Barents to the Arctic Regions in 1596 and the journal of captain Junge on his hunting trip from Tromsø to Svalbard in 1834.It is nearly 240 years between this to voyages. The first journal is known as the earliest report from the arctic era. Gerrit de Veer adds instructive copper engravings to his text and give us insight in the crews meeting with this new land. Captain Junges journal is found together with his dead crew in a house in a fjord nearby Ny-Ålesund and has no drawings, but word. Both of these journals may be read as sources of the knowledge and understanding of the polar region. They might also unveil the ideas of how to deal with and survive under the challenges that is given. In addition one can ask if the sources can tell us more about how men describe their challenges. Can the way they expressed themselves in the journals give us an understanding of masculinity? And not least help us to create good questions of the change in the ideas of masculinities which is said to follow the change in understanding of the wilderness.

  12. Fluorescence detection: SPIE volume 743

    International Nuclear Information System (INIS)

    Menzel, E.R.

    1987-01-01

    This book contains proceedings arranged into four sessions. They are: Fluorescence spectroscopic techniques; Fluorescence in analysis and materials characterization; Fluorescence in medicine and biochemistry; and Fluorescence in criminalistics

  13. Fluorescence detection: SPIE volume 743

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, E.R.

    1987-01-01

    This book contains proceedings arranged into four sessions. They are: Fluorescence spectroscopic techniques; Fluorescence in analysis and materials characterization; Fluorescence in medicine and biochemistry; and Fluorescence in criminalistics.

  14. Biosynthesis of bacterial aromatic polyketides.

    Science.gov (United States)

    Zhan, Jixun

    2009-01-01

    Aromatic polyketides represent important members of the family of polyketides, which have displayed a wide assortment of bioactive properties, such as antibacterial, antitumor, and antiviral activities. Bacterial aromatic polyketides are mainly synthesized by type II polyketide synthases (PKSs). Whereas malonyl-CoA is exclusively used as the extender unit, starter units can vary in different aromatic polyketide biosynthetic pathways, leading to a variety of polyketide backbones. Once the polyketide chains are elongated by the minimal PKSs to the full length, the immediate tailoring enzymes including ketoreductases, oxygenases and cyclases will work on the nascent chains to form aromatic structures, which will be further decorated by those late tailoring enzymes such as methyltransferases and glycosyltransferases. The mechanistic studies on the biosynthetic pathways of aromatic polyketides such as oxytetracycline and pradimicin A have been extensively carried out in recent years. Engineered biosynthesis of novel "unnatural" polyketides has been achieved in heterologous hosts such as Streptomyces coelicolor and Escherichia coli. This review covers the most recent advances in aromatic polyketide biosynthesis, which provide new enzymes or methods for building novel polyketide biosynthetic machinery.

  15. Fatty acid biosynthesis in actinomycetes

    Science.gov (United States)

    Gago, Gabriela; Diacovich, Lautaro; Arabolaza, Ana; Tsai, Shiou-Chuan; Gramajo, Hugo

    2011-01-01

    All organisms that produce fatty acids do so via a repeated cycle of reactions. In mammals and other animals, these reactions are catalyzed by a type I fatty acid synthase (FAS), a large multifunctional protein to which the growing chain is covalently attached. In contrast, most bacteria (and plants) contain a type II system in which each reaction is catalyzed by a discrete protein. The pathway of fatty acid biosynthesis in Escherichia coli is well established and has provided a foundation for elucidating the type II FAS pathways in other bacteria (White et al., 2005). However, fatty acid biosynthesis is more diverse in the phylum Actinobacteria: Mycobacterium, possess both FAS systems while Streptomyces species have only the multi-enzyme FAS II system and Corynebacterium species exclusively FAS I. In this review we present an overview of the genome organization, biochemical properties and physiological relevance of the two FAS systems in the three genera of actinomycetes mentioned above. We also address in detail the biochemical and structural properties of the acyl-CoA carboxylases (ACCases) that catalyzes the first committed step of fatty acid synthesis in actinomycetes, and discuss the molecular bases of their substrate specificity and the structure-based identification of new ACCase inhibitors with anti-mycobacterial properties. PMID:21204864

  16. Modification of membrane properties and fatty acids biosynthesis-related genes in Escherichia coli and Staphylococcus aureus: Implications for the antibacterial mechanism of naringenin.

    Science.gov (United States)

    Wang, Lang-Hong; Zeng, Xin-An; Wang, Man-Sheng; Brennan, Charles S; Gong, Deming

    2018-02-01

    In this work, modifications of cell membrane fluidity, fatty acid composition and fatty acid biosynthesis-associated genes of Escherichia coli ATCC 25922 (E. coli) and Staphylococcus aureus ATCC 6538 (S. aureus), during growth in the presence of naringenin (NAR), one of the natural antibacterial components in citrus plants, was investigated. Compared to E. coli, the growth of S. aureus was significantly inhibited by NAR in low concentrations. Combination of gas chromatography-mass spectrometry with fluorescence polarization analysis revealed that E. coli and S. aureus cells increased membrane fluidity by altering the composition of membrane fatty acids after exposure to NAR. For example, E. coli cells produced more unsaturated fatty acids (from 18.5% to 43.3%) at the expense of both cyclopropane and saturated fatty acids after growth in the concentrations of NAR from 0 to 2.20mM. For S. aureus grown with NAR at 0 to 1.47mM, the relative proportions of anteiso-branched chain fatty acids increased from 37.2% to 54.4%, whereas iso-branched and straight chain fatty acids decreased from 30.0% and 33.1% to 21.6% and 23.7%, respectively. Real time q-PCR analysis showed that NAR at higher concentrations induced a significant down-regulation of fatty acid biosynthesis-associated genes in the bacteria, with the exception of an increased expression of fabA gene. The minimum inhibitory concentration (MIC) of NAR against these two bacteria was determined, and both of bacteria underwent morphological changes after exposure to 1.0 and 2.0 MIC. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Simultaneous measurements of fluorescence lifetimes, anisotropy, and FRAP recovery curves

    Science.gov (United States)

    Levitt, James A.; Chung, Pei-Hua; Alibhai, Dominic R.; Suhling, Klaus

    2011-02-01

    We present fluorescence lifetime imaging (FLIM) and fluorescence anisotropy imaging along with translational diffusion measurements of living cells labelled with green fluorescent protein (GFP) recorded in a single experiment. The experimental set-up allows for time and polarization-resolved fluorescence images to be measured in every frame of a fluorescence recovery after photobleaching (FRAP) series. We have validated the method using rhodamine 123 in homogeneous solution prior to measurements of living A431 cells labelled with cdc42-GFP, for which the FRAP recovery exhibits an immobile fraction and the rotational mobility of the protein is hindered while the fluorescence lifetime fairly homogeneous across the cell. By eliminating the need for sequential measurements to extract fluorescence lifetimes and molecular diffusion coefficients we remove artefacts arising from changes in sample morphology and excessive photobleaching during sequential experiments.

  18. Regulatory variability of camalexin biosynthesis.

    Science.gov (United States)

    Schuhegger, Regina; Rauhut, Thomas; Glawischnig, Erich

    2007-05-01

    The anthranilate synthase ASA1, CYP79B2 and CYP71B15 (PAD3) are biosynthetic genes of the Arabidopsis phytoalexin camalexin, which are induced after pathogen infection and abiotic treatments like silver nitrate spraying. The natural variation of camalexin biosynthesis in response to Pseudomonas syringae infection was determined in several ecotypes, and differential CYP71B15 regulation as a potential basis for this variation was investigated. The expression of camalexin biosynthetic genes was restricted to the tissue undergoing cell death. After droplet infection with Alternaria alternata, a potent camalexin inducer in the Col-0 ecotype, camalexin formation and the induction of ASA1, CYP79B2 and CYP71B15 were strictly co-localized with the infection site.

  19. Polarized electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Prepost, R. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented.

  20. Monoterpene biosynthesis potential of plant subcellular compartments

    NARCIS (Netherlands)

    Dong, L.; Jongedijk, E.J.; Bouwmeester, H.J.; Krol, van der A.R.

    2016-01-01

    Subcellular monoterpene biosynthesis capacity based on local geranyl diphosphate (GDP) availability or locally boosted GDP production was determined for plastids, cytosol and mitochondria. A geraniol synthase (GES) was targeted to plastids, cytosol, or mitochondria. Transient expression in Nicotiana

  1. Antibacterial Targets in Fatty Acid Biosynthesis

    Science.gov (United States)

    Wright, H. Tonie; Reynolds, Kevin A.

    2008-01-01

    Summary The fatty acid biosynthesis pathway is an attractive but still largely unexploited target for development of new anti-bacterial agents. The extended use of the anti-tuberculosis drug isoniazid and the antiseptic triclosan, which are inhibitors of fatty acid biosynthesis, validates this pathway as a target for anti-bacterial development. Differences in subcellular organization of the bacterial and eukaryotic multi-enzyme fatty acid synthase systems offer the prospect of inhibitors with host vs. target specificity. Platensimycin, platencin, and phomallenic acids, newly discovered natural product inhibitors of the condensation steps in fatty acid biosynthesis, represent new classes of compounds with antibiotic potential. An almost complete catalogue of crystal structures for the enzymes of the type II fatty acid biosynthesis pathway can now be exploited in the rational design of new inhibitors, as well as the recently published crystal structures of type I FAS complexes. PMID:17707686

  2. Lincomycin, cultivation of producing strains and biosynthesis

    Czech Academy of Sciences Publication Activity Database

    Spížek, Jaroslav; Řezanka, Tomáš

    2004-01-01

    Roč. 63, - (2004), s. 510-519 ISSN 0175-7598 Institutional research plan: CEZ:AV0Z5020903 Keywords : lincomycin * cultivation * biosynthesis Subject RIV: EE - Microbiology, Virology Impact factor: 2.358, year: 2004

  3. Control of tylosin biosynthesis in Streptomyces fradiae.

    Science.gov (United States)

    Cundliffe, Eric

    2008-09-01

    Tylosin biosynthesis is controlled in cascade fashion by multiple transcriptional regulators, acting positively or negatively, in conjunction with a signalling ligand that acts as a classical inducer. The roles of regulatory gene products have been characterized by a combination of gene expression analysis and fermentation studies, using engineered strains of S. fradiae in which specific genes were inactivated or overexpressed. Among various novel features of the regulatory model, involvement of the signalling ligand is not essential for tylosin biosynthesis.

  4. Biosynthesis of antibiotic chuangxinmycin from Actinoplanes tsinanensis

    Directory of Open Access Journals (Sweden)

    Yuanyuan Shi

    2018-03-01

    Full Text Available Chuangxinmycin is an antibiotic isolated from Actinoplanes tsinanensis CPCC 200056 in the 1970s with a novel indole-dihydrothiopyran heterocyclic skeleton. Chuangxinmycin showed in vitro antibacterial activity and in vivo efficacy in mouse infection models as well as preliminary clinical trials. But the biosynthetic pathway of chuangxinmycin has been obscure since its discovery. Herein, we report the identification of a stretch of DNA from the genome of A. tsinanensis CPCC 200056 that encodes genes for biosynthesis of chuangxinmycin by bioinformatics analysis. The designated cxn cluster was then confirmed to be responsible for chuangxinmycin biosynthesis by direct cloning and heterologous expressing in Streptomyces coelicolor M1146. The cytochrome P450 CxnD was verified to be involved in the dihydrothiopyran ring closure reaction by the identification of seco-chuangxinmycin in S. coelicolor M1146 harboring the cxn gene cluster with an inactivated cxnD. Based on these results, a plausible biosynthetic pathway for chuangxinmycin biosynthesis was proposed, by hijacking the primary sulfur transfer system for sulfur incorporation. The identification of the biosynthetic gene cluster of chuangxinmycin paves the way for elucidating the detail biochemical machinery for chuangxinmycin biosynthesis, and provides the basis for the generation of novel chuangxinmycin derivatives by means of combinatorial biosynthesis and synthetic biology. KEY WORDS: Chuangxinmycin, Actinoplanes tsinanensis, Biosynthesis gene cluster, Heterologous expression, Cytochrome P450, Seco-chuangxinmycin, C–S bond formation, Sulfur incorporation

  5. Selective nonspecific solvation under dielectric saturation and fluorescence spectra of dye solutions in binary solvents.

    Science.gov (United States)

    Bakhshiev, N G; Kiselev, M B

    1991-09-01

    The influence of selective nonspecific solvation on the fluorescence spectra of three substitutedN-methylphthalimides in a binary solvent system consisting of a nonpolar (n-heptane) and a polar (pyridine) component has been studied under conditions close to dielectric saturation. The substantially nonlinearity of the effect is confirmation that the spectral shifts of fluorescence bands depend on the number of polar solvent molecules involved in solvating the dye molecule. The measured fluorescence spectral shifts determined by substituting one nonpolar solvent molecula with a polar one in the proximity of the dye molecule agree quantitatively with the forecasts of the previously proposed semiempirical theory which describes this nonlinear solvation phenomenon.

  6. Geographical Income Polarization

    DEFF Research Database (Denmark)

    Azhar, Hussain; Jonassen, Anders Bruun

    inter municipal income inequality. Counter factual simulations show that rising property prices to a large part explain the rise in polarization. One side-effect of polarization is tendencies towards a parallel polarization of residence location patterns, where low skilled individuals tend to live......In this paper we estimate the degree, composition and development of geographical income polarization based on data at the individual and municipal level in Denmark from 1984 to 2002. Rising income polarization is reconfirmed when applying new polarization measures, the driving force being greater...

  7. Reviews in fluorescence 2010

    CERN Document Server

    Geddes, Chris D

    2011-01-01

    ""Reviews in Fluorescence 2010"", the seventh volume of the book serial from Springer, serves as a comprehensive collection of current trends and emerging hot topics in the field of fluorescence and closely related disciplines. It summarizes the year's progress in fluorescence and its applications, with authoritative analytical reviews specialized enough to be attractive to professional researchers, yet also appealing to the wider audience of scientists in related disciplines of fluorescence. ""Reviews in Fluorescence"" offers an essential reference material for any lab working in the fluoresc

  8. Proceedings of the Japan-US workshop on plasma polarization spectroscopy and the international seminar on plasma polarization spectroscopy

    International Nuclear Information System (INIS)

    Fujimoto, Takashi; Beiersdorfer, Peter

    1998-06-01

    The international meeting on Plasma Polarization Spectroscopy (PPS) was held in Kyoto during January 26-28, 1998. This Proceedings book includes the papers of the talks given at the meeting. These include: overviews of PPS from the aspects of atomic physics, and of plasma physics; several PPS and MSE (motional Stark effect) experiments on magnetically confined plasmas and a laser-produced plasma; polarized laser-induced fluorescence spectroscopy, several experiments on EBITs (electron beam ion trap) and their theoretical interpretations; polarized profiles of spectral lines, basic formulation of PPS; inelastic and elastic electron collisions leading to polarized atomic states; polarization in recombining plasma; relationship between the collisional polarization relaxation and the line broadening; and characteristics of the plasma produced by very short pulse and high power laser irradiation. The 19 of the presented papers are indexed individually. (J.P.N.)

  9. Polarized Light Corridor Demonstrations.

    Science.gov (United States)

    Davies, G. R.

    1990-01-01

    Eleven demonstrations of light polarization are presented. Each includes a brief description of the apparatus and the effect demonstrated. Illustrated are strain patterns, reflection, scattering, the Faraday Effect, interference, double refraction, the polarizing microscope, and optical activity. (CW)

  10. Optical-Fiber Fluorosensors With Polarized Light Sources

    Science.gov (United States)

    Egalon, Claudio O.; Rogowski, Robert S.

    1995-01-01

    Chemiluminescent and/or fluorescent molecules in optical-fiber fluorosensors oriented with light-emitting dipoles along transverse axis. Sensor of proposed type captures greater fraction of chemiluminescence or fluorescence and transmits it to photodetector. Transverse polarization increases sensitivity. Basic principles of optical-fiber fluorosensors described in "Making Optical-Fiber Chemical Sensors More Sensitive" (LAR-14525), "Improved Optical-Fiber Chemical Sensors" (LAR-14607), and "Improved Optical-Fiber Temperature Sensors" (LAR-14647).

  11. Fluorescence anisotropy characterization of urine in the diagnosis of cancer

    Science.gov (United States)

    Rajasekaran, Ramu; Brindha, Elumalai; Sivabalan, Shanmugam; Aruna, Prakasa Rao; Koteeswaran, Dornadula; Ganesan, Singaravelu

    2016-03-01

    Cervical cancer is considered as the second most commonly occurring malignancy among women, next to breast cancer. It is well known that most of the cancer patients diagnosed with advanced stages and there is a pressing need for improved methods to detect cancer at its initial stages. Many techniques have been adopted for the diagnosis of cervical cancer. Among these, fluorescence polarization spectroscopy is a complementary technique of fluorescence spectroscopy which helps us to elucidate the spectral characteristics which highly depend on pH, viscosity and local environment. Since urine has many metabolites and the measurement of native fluorescence of urine, in principle, able to provide an indication of a number of health conditions, attempts were made to study fluorescence anisotropic characterization of the human urine of cervical cancer patients and normal subjects. Significant differences were observed between the anisotropic and polarization values of cancer subjects and normal subjects.

  12. Fluorescent optical position sensor

    Science.gov (United States)

    Weiss, Jonathan D.

    2005-11-15

    A fluorescent optical position sensor and method of operation. A small excitation source side-pumps a localized region of fluorescence at an unknown position along a fluorescent waveguide. As the fluorescent light travels down the waveguide, the intensity of fluorescent light decreases due to absorption. By measuring with one (or two) photodetectors the attenuated intensity of fluorescent light emitted from one (or both) ends of the waveguide, the position of the excitation source relative to the waveguide can be determined by comparing the measured light intensity to a calibrated response curve or mathematical model. Alternatively, excitation light can be pumped into an end of the waveguide, which generates an exponentially-decaying continuous source of fluorescent light along the length of the waveguide. The position of a photodetector oriented to view the side of the waveguide can be uniquely determined by measuring the intensity of the fluorescent light emitted radially at that location.

  13. Reviews in fluorescence 2008

    CERN Document Server

    Geddes, Chris D

    2010-01-01

    This volume serves as a comprehensive collection of current trends and emerging hot topics in the field of fluorescence spectroscopy. It summarizes the year's progress in fluorescence and its applications as well as includes authoritative analytical reviews.

  14. Fluorescence correlation spectroscopy

    NARCIS (Netherlands)

    Hink, M.A.; Verveer, P.J.

    2015-01-01

    Fluorescence fluctuation spectroscopy techniques allow the quantification of fluorescent molecules present at the nanomolar concentration level. After a brief introduction to the technique, this chapter presents a protocol including background information in order to measure and quantify the

  15. Biosynthesis and transport of lysosomal alpha-glucosidase in the human colon carcinoma cell-line Caco-2: secretion from the apical surface

    NARCIS (Netherlands)

    Klumperman, J.; Fransen, J.A.; Boekestijn, J.C.; Oude Elferink, R.P.; Matter, K.; Hauri, H.P.; Tager, J.M.; Ginsel, L.A.

    1991-01-01

    The human adenocarcinoma cell line Caco-2 was used for studies on the biosynthesis and transport of lysosomal acid alpha-glucosidase in polarized epithelial cells. Metabolic labelling revealed that in Caco-2 cells alpha-glucosidase is synthesized as a precursor form of 110 x 10(3) Mr. This form is

  16. Polarized Moessbauer transitions

    International Nuclear Information System (INIS)

    Barb, D.

    1975-01-01

    Theoretical aspects of the emission, absorption and scattering of polarized gamma rays are reviewed for a general case of combined magnetic and electric hyperfine interactions; various possibilities of obtaining polarized gamma sources are described and examples are given of the applications of Moessbauer spectroscopy with polarized gamma rays in solving problems of solid state physics. (A.K.)

  17. Resonance fluorescence from an atom in a squeezed vacuum

    Science.gov (United States)

    Carmichael, H. J.; Lane, A. S.; Walls, D. F.

    1987-06-01

    The fluorescent spectrum for a two-level atom which is damped by a squeezed vacuum shows striking differences from the spectrum for ordinary resonance fluorescence. For strong coherent driving fields the Mollow triplet depends on the relative phase of the driving field and the squeezed vacuum field. The central peak may have either subnatural linewidth or supernatural linewidth depending on this phase. The mean atomic polarization also shows a phase sensitivity.

  18. Analysis of sublethal arsenic toxicity to Ceratophyllum demersum: subcellular distribution of arsenic and inhibition of chlorophyll biosynthesis

    Czech Academy of Sciences Publication Activity Database

    Mishra, S.; Alfred, M.; Sobotka, Roman; Andresen, E.; Falkenberg, G.; Küpper, Hendrik

    2016-01-01

    Roč. 67, č. 15 (2016), s. 4639-4646 ISSN 0022-0957 R&D Projects: GA ČR GBP501/12/G055; GA MŠk(CZ) LO1416 Institutional support: RVO:61388971 ; RVO:60077344 Keywords : arsenic toxicity * chlorophyll biosynthesis * subcellular distribution of arsenic * synchrotron micro-X-ray fluorescence Subject RIV: EE - Microbiology, Virology; CE - Biochemistry (BC-A) Impact factor: 5.830, year: 2016

  19. The Physics of Polarization

    Science.gov (United States)

    Landi Degl'Innocenti, Egidio

    2015-10-01

    The introductory lecture that has been delivered at this Symposium is a condensed version of an extended course held by the author at the XII Canary Island Winter School from November 13 to November 21, 2000. The full series of lectures can be found in Landi Degl'Innocenti (2002). The original reference is organized in 20 Sections that are here itemized: 1. Introduction, 2. Description of polarized radiation, 3. Polarization and optical devices: Jones calculus and Muller matrices, 4. The Fresnel equations, 5. Dichroism and anomalous dispersion, 6. Polarization in everyday life, 7. Polarization due to radiating charges, 8. The linear antenna, 9. Thomson scattering, 10. Rayleigh scattering, 11. A digression on Mie scattering, 12. Bremsstrahlung radiation, 13. Cyclotron radiation, 14. Synchrotron radiation, 15. Polarization in spectral lines, 16. Density matrix and atomic polarization, 17. Radiative transfer and statistical equilibrium equations, 18. The amplification condition in polarized radiative transfer, and 19. Coupling radiative transfer and statistical equilibrium equations.

  20. The Spatial Organization of Glucosinolate Biosynthesis

    DEFF Research Database (Denmark)

    Nintemann, Sebastian

    between the individual classes of glucosinolates under constitutive and induced conditions and identified the source tissues of these defense compounds. Protein-protein interaction studies were carried out to investigate the subcellular organization of glucosinolate biosynthesis. We identified a family...... resistance and nutritional value and many plant specialized metabolites are of high value due to their health promoting characteristics. Glucosinolates are defense compounds found in many crops from the Brassicaceae family and are of high interest because of their nutritional and antinutritional properties...... cells is an open question. Likewise, it is not known how glucosinolate biosynthesis is orchestrated at the subcellular level. These open questions were addressed with several approaches in this project, with the aim of shedding light on the spatial organization of glucosinolate biosynthesis from...

  1. Functional and Evolutionary Relationship between Arginine Biosynthesis and Prokaryotic Lysine Biosynthesis through α-Aminoadipate

    Science.gov (United States)

    Miyazaki, Junichi; Kobashi, Nobuyuki; Nishiyama, Makoto; Yamane, Hisakazu

    2001-01-01

    Our previous studies revealed that lysine is synthesized through α-aminoadipate in an extremely thermophilic bacterium, Thermus thermophilus HB27. Sequence analysis of a gene cluster involved in the lysine biosynthesis of this microorganism suggested that the conversion from α-aminoadipate to lysine proceeds in a way similar to that of arginine biosynthesis. In the present study, we cloned an argD homolog of T. thermophilus HB27 which was not included in the previously cloned lysine biosynthetic gene cluster and determined the nucleotide sequence. A knockout of the argD-like gene, now termed lysJ, in T. thermophilus HB27 showed that this gene is essential for lysine biosynthesis in this bacterium. The lysJ gene was cloned into a plasmid and overexpressed in Escherichia coli, and the LysJ protein was purified to homogeneity. When the catalytic activity of LysJ was analyzed in a reverse reaction in the putative pathway, LysJ was found to transfer the ɛ-amino group of N2-acetyllysine, a putative intermediate in lysine biosynthesis, to 2-oxoglutarate. When N2-acetylornithine, a substrate for arginine biosynthesis, was used as the substrate for the reaction, LysJ transferred the δ-amino group of N2-acetylornithine to 2-oxoglutarate 16 times more efficiently than when N2-acetyllysine was the amino donor. All these results suggest that lysine biosynthesis in T. thermophilus HB27 is functionally and evolutionarily related to arginine biosynthesis. PMID:11489859

  2. Triterpenoid biosynthesis in Euphorbia lathyris latex

    International Nuclear Information System (INIS)

    Hawkins, D.R.

    1987-11-01

    The structures of triterpenols, not previously been known, from Euphorbia lathyris latex are reported. A method for quantifying very small amounts of these compounds was developed. Concerning the biochemistry of the latex, no exogenous cofactors were required for the biosynthesis and the addition of compounds such as NADPAH and ATP do not stimulate the biosynthesis. The addition of DTE or a similar anti-oxidant was found to help reduce the oxidation of the latex, thus increasing the length of time that the latex remains active. The requirement of a divalent cation and the preference for Mn in the pellet was observed. The effect of several inhibitors on the biosynthesis of the triterpenoids was examined. Mevinolin was found to inhibit the biosynthesis of the triterpenoids from acetate, but not mevalonate. A dixon plot of the inhibition of acetate incorporation showed an I 50 concentration of 3.2 μM. Fenpropimorph was found to have little or no effect on the biosynthesis. Tridemorph was found to inhibit the biosynthesis of all of the triterpenoids with an I 50 of 4 μM. It was also observed that the cyclopropyl containing triterpenols, cycloartenol and 24-methylenecycloartenol were inhibited much more strongly than those containing an 8-9 double bond, lanosterol and 24-methylenelanosterol. The evidence indicates, but does not definetely prove, that lanosterol and 24-methylenelanosterol are not made from cycloartenol and 24-methylenecycloartenol via a ring-opening enzyme such as cycloeucalenol-obtusifoliol isomerase. The possibilty that cycloartenol is made via lanosterol was investigated by synthesizing 4-R-4- 3 H-mevalonic acid and incubating latex with a mixture of this and 14 C-mevalonic acid. From the 3 H/ 14 C ratio it was shown that cycloartenol and 24-methylenecycloartenol are not made via an intermediate containing as 8-9 double bond. 88 refs., 15 figs., 30 tabs

  3. Nucleoside antibiotics: biosynthesis, regulation, and biotechnology.

    Science.gov (United States)

    Niu, Guoqing; Tan, Huarong

    2015-02-01

    The alarming rise in antibiotic-resistant pathogens has coincided with a decline in the supply of new antibiotics. It is therefore of great importance to find and create new antibiotics. Nucleoside antibiotics are a large family of natural products with diverse biological functions. Their biosynthesis is a complex process through multistep enzymatic reactions and is subject to hierarchical regulation. Genetic and biochemical studies of the biosynthetic machinery have provided the basis for pathway engineering and combinatorial biosynthesis to create new or hybrid nucleoside antibiotics. Dissection of regulatory mechanisms is leading to strategies to increase the titer of bioactive nucleoside antibiotics. Copyright © 2014. Published by Elsevier Ltd.

  4. Combinatorial Biosynthesis of Polyketides – A Perspective

    Science.gov (United States)

    Wong, Fong T.; Khosla, Chaitan

    2012-01-01

    Since their discovery, polyketide synthases have been attractive targets of biosynthetic engineering to make “unnatural” natural products. Although combinatorial biosynthesis has made encouraging advances over the past two decades, the field remains in its infancy. In this enzyme-centric perspective, we discuss the scientific and technological challenges that could accelerate the adoption of combinatorial biosynthesis as a method of choice for the preparation of encoded libraries of bioactive small molecules. Borrowing a page from the protein structure prediction community, we propose a periodic challenge program to vet the most promising methods in the field, and to foster the collective development of useful tools and algorithms. PMID:22342766

  5. Method for determining heterologous biosynthesis pathways

    KAUST Repository

    Gao, Xin

    2017-08-10

    The present invention relates to a method and system for dynamically analyzing, determining, predicting and displaying ranked suitable heterologous biosynthesis pathways for a specified host. The present invention addresses the problem of finding suitable pathways for the endogenous metabolism of a host organism because the efficacy of heterologous biosynthesis is affected by competing endogenous pathways. The present invention is called MRE (Metabolic Route Explorer), and it was conceived and developed to systematically and dynamically search for, determine, analyze, and display promising heterologous pathways while considering competing endogenous reactions in a given host organism.

  6. Convergent Evolution of Ergothioneine Biosynthesis in Cyanobacteria.

    Science.gov (United States)

    Liao, Cangsong; Seebeck, Florian P

    2017-11-02

    Biosynthesis of N-α-trimethyl-2-thiohistidine (ergothioneine) is a frequent trait in cyanobacteria. This sulfur compound may provide essential relief from oxidative stress related to oxygenic photosynthesis. The central steps in ergothioneine biosynthesis are catalyzed by a histidine methyltransferase and an iron-dependent sulfoxide synthase. In this report, we present evidence that some cyanobacteria recruited and adapted a sulfoxide synthase from a different biosynthetic pathway to make ergothioneine. The discovery of a second origin of ergothioneine production underscores the physiological importance of this metabolite and highlights the evolutionary malleability of the thiohistidine biosynthetic machinery. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Biosynthesis of silver nanoparticles by Aspergillus niger , Fusarium ...

    African Journals Online (AJOL)

    ... scanning electron microscope (SEM). Results indicate the synthesis of silver nanoparticles in the reaction mixture. The synthesis of nanoparticles would be suitable for developing a microbial nanotechnology biosynthesis process for mass scale production. Keywords: Silver nanoparticles, biosynthesis, fungi, Aspergillus.

  8. Monitoring membrane hydration with 2-(dimethylamino)-6-acylnaphtalenes fluorescent probes

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2015-01-01

    comparative studies. This chapter presents a short historical overview about these fluorescent reporters, discusses on different models proposed to explain their sensitivity to membrane hydration, and includes relevant examples from experiments performed in artificial and biological membranes......., were used to study membrane lateral structure and associated dynamics. Once incorporated into membranes, the (nanosecond) fluorescent decay of these probes is strongly affected by changes in the local polarity and relaxation dynamics of restricted water molecules existing at the membrane....../water interface. For instance, when glycerophospholipid containing membranes undertake a solid ordered (gel) to liquid disordered phase transition the fluorescence emission maximum of these probes shift ~ 50 nm with a significant change in their fluorescence lifetime. Furthermore, the fluorescence parameters...

  9. Nanoantenna array-induced fluorescence enhancement and reduced lifetimes

    DEFF Research Database (Denmark)

    Bakker, R. M.; Drachev, V. P.; Liu, Z.

    2008-01-01

    Enhanced fluorescence is observed from dye molecules interacting with optical nanoantenna arrays. Elliptical gold dimers form individual nanoantennae with tunable plasmon resonances depending upon the geometry of the two particles and the size of the gap between them. A fluorescent dye, Rhodamine...... 800, is uniformly embedded in a dielectric host that coats the nanoantennae. The nanoantennae act to enhance the dye absorption. In turn, emission from the dye drives the plasmon resonance of the antennae; the nanoantennae act to enhance the fluorescence signal and change the angular distribution...... of emission. These effects depend upon the overlap of the plasmon resonance with the excitation wavelength and the fluorescence emission band. A decreased fluorescence lifetime is observed along with highly polarized emission that displays the characteristics of the nanoantenna's dipole mode. Being able...

  10. Surface plasmon-coupled emission from shaped PMMA films doped with fluorescence molecules.

    Science.gov (United States)

    Zhang, D G; Moh, K J; Yuan, X-C

    2010-06-07

    Surface plasmon-coupled emission from shaped PMMA films doped with randomly oriented fluorescence molecules was investigated. Experimental results show that for different shapes, such as triangle or circular structures, the SPCE ring displays different intensity patterns. For a given shape, it was observed that the relative position and polarization of an incident laser spot on the shaped PMMA can be used to adjust the fluorescence intensity distribution of the SPCE ring. The proposed method enables controlling the fluorescence emission in azimuthal direction in addition to the radial angle controlled by common SPCE, which will further enhances the fluorescence collection efficiency and has applications in fluorescence sensing, imaging and so on.

  11. [Review] Polarization and Polarimetry

    Science.gov (United States)

    Trippe, Sascha

    2014-02-01

    Polarization is a basic property of light and is fundamentally linked to the internal geometry of a source of radiation. Polarimetry complements photometric, spectroscopic, and imaging analyses of sources of radiation and has made possible multiple astrophysical discoveries. In this article I review (i) the physical basics of polarization: electromagnetic waves, photons, and parameterizations; (ii) astrophysical sources of polarization: scattering, synchrotron radiation, active media, and the Zeeman, Goldreich-Kylafis, and Hanle effects, as well as interactions between polarization and matter (like birefringence, Faraday rotation, or the Chandrasekhar-Fermi effect); (iii) observational methodology: on-sky geometry, influence of atmosphere and instrumental polarization, polarization statistics, and observational techniques for radio, optical, and X/γ wavelengths; and (iv) science cases for astronomical polarimetry: solar and stellar physics, planetary system bodies, interstellar matter, astrobiology, astronomical masers, pulsars, galactic magnetic fields, gamma-ray bursts, active galactic nuclei, and cosmic microwave background radiation.

  12. Biosynthesis and metabolic pathways of pivalic acid

    Czech Academy of Sciences Publication Activity Database

    Řezanka, Tomáš; Kolouchová, I.; Čejková, A.; Sigler, Karel

    2012-01-01

    Roč. 95, č. 6 (2012), s. 1371-1376 ISSN 0175-7598 R&D Projects: GA ČR(CZ) GAP503/11/0215 Institutional support: RVO:61388971 Keywords : Pivalic acid * Isooctane * Biosynthesis Subject RIV: EE - Microbiology, Virology Impact factor: 3.689, year: 2012

  13. Combinatorial biosynthesis of medicinal plant secondary metabolites

    NARCIS (Netherlands)

    Julsing, Mattijs K.; Koulman, Albert; Woerdenbag, Herman J.; Quax, Wim J.; Kayser, Oliver

    2006-01-01

    Combinatorial biosynthesis is a new tool in the generation of novel natural products and for the production of rare and expensive natural products. The basic concept is combining metabolic pathways in different organisms on a genetic level. As a consequence heterologous organisms provide precursors

  14. Biosynthesis of silver nanoparticles synthesized by Aspergillus

    Indian Academy of Sciences (India)

    In the present study, biosynthesis of silver nanoparticles and its antioxidant, antimicrobial and cytotoxic activities were investigated. Silver nanoparticles were extracellularly synthesized using Aspergillus flavus and the formation of nanoparticles was observed after 72 h of incubation. The results recorded from colour ...

  15. Bile acid biosynthesis and its regulation

    Directory of Open Access Journals (Sweden)

    Areta Hebanowska

    2010-10-01

    Full Text Available Bile acid biosynthesis is the main pathway of cholesterol catabolism. Bile acids are more soluble than cholesterol so are easier to excrete. As amphipathic molecules they participate in lipid digestion and absorption in the intestine and they help to excrete free cholesterol with bile. They are also ligands for nuclear receptors regulating the expression of genes involved in cholesterol metabolism. Interconversion of cholesterol into bile acids is an important point of its homeostasis. Seventeen enzymes are engaged in this process and many of them are cytochromes P450. Bile acid synthesis initiation may proceed with the “classical” pathway (starting with cholesterol hydroxylation at the C7α position or the “alternative” pathway (starting with cholesterol hydroxylation at the C27 position. Two additional pathways are possible, though their quantitative significance is small (initiated with cholesterol hydroxylations of C24 and C25 positions. Oxysterols produced are not only intermediates of bile acid biosynthesis but also important regulators of metabolism. Bile acid biosynthesis takes place in the liver, but some enzymes are also present in other organs, where they participate in regulation of cholesterol metabolism. Those enzymes are potential targets for new drugs against cholesterol metabolism disturbances. This article is a brief description of the bile acid biosynthesis pathway and participating enzymes.

  16. Biosynthesis of polyhydroxyalkanotes in wildtype yeasts | Desuoky ...

    African Journals Online (AJOL)

    Biosynthesis of the biodegradable polymers polyhydroxyalkanotes (PHAs) are studied extensively in wild type and genetically modified prokaryotic cells, however the content and structure of PHA in wild type yeasts are not well documented. The purpose of this study was to screen forty yeast isolates collected from different ...

  17. Unedoside derivatives in Nuxia and their biosynthesis

    DEFF Research Database (Denmark)

    Jensen, Søren Rosendal; Ravnkilde, Lene; Schripsema, Jan

    1998-01-01

    isolated, while from N. oppositifolia 2 "-acetyl-3 "-benzoyl-nuxioside was obtained. Both plants contained verbascoside. The biosynthesis of unedoside in N. floribunda was investigated and deoxyloganic acid was found to be a precursor, similar to wh;lt was found for the eight-carbon iridoids in Thunbergia...

  18. Biosynthesis of furanochromones in Pimpinella monoica

    Indian Academy of Sciences (India)

    polyketide origin of their aromatic and pyrone rings while the furan ring originates via an acetate-mevalonate pathway. The plant also utilises glycine and leucine as substrate via acetate. Biotransformation of 3-H-visnagin to (6) but not to (2) was also observed. Keywords. Biosynthesis; furochromones; polyketide origin; ...

  19. Biosynthesis of silver nanoparticles synthesized by Aspergillus ...

    Indian Academy of Sciences (India)

    In the present study, biosynthesis of silver nanoparticles and its antioxidant, antimicrobial and cytotoxic activities were investigated. Silver nanoparticles were extracellularly synthesized using Aspergillus flavus and the formation of nanoparticles was observed after 72 h of incubation. The results recorded from colour ...

  20. Polarization feedback laser stabilization

    Science.gov (United States)

    Esherick, P.; Owyoung, A.

    1987-09-28

    A system for locking two Nd:YAG laser oscillators includes an optical path for feeding the output of one laser into the other with different polarizations. Elliptical polarization is incorporated into the optical path so that the change in polarization that occurs when the frequencies coincide may be detected to provide a feedback signal to control one laser relative to the other. 4 figs.

  1. Polarization in Sagittarius A*

    OpenAIRE

    Bower, Geoffrey C.

    2000-01-01

    We summarize the current state of polarization observations of Sagittarius A*, the compact radio source and supermassive black hole candidate in the Galactic Center. These observations are providing new tools for understanding accretion disks, jets and their environments. Linear polarization observations have shown that Sgr A* is unpolarized at frequencies as high as 86 GHz. However, recent single-dish observations indicate that Sgr A* may have strong linear polarization at frequencies higher...

  2. Laser detection of spin-polarized hydrogen from HCl and HBr photodissociation: comparison of H- and halogen-atom polarizations.

    Science.gov (United States)

    Sofikitis, Dimitris; Rubio-Lago, Luis; Bougas, Lykourgos; Alexander, Andrew J; Rakitzis, T Peter

    2008-10-14

    Thermal HCl and HBr molecules were photodissociated using circularly polarized 193 nm light, and the speed-dependent spin polarization of the H-atom photofragments was measured using polarized fluorescence at 121.6 nm. Both polarization components, described by the a(0)(1)(perpendicular) and Re[a(1)(1)(parallel, perpendicular)] parameters which arise from incoherent and coherent dissociation mechanisms, are measured. The values of the a(0)(1)(perpendicular) parameter, for both HCl and HBr photodissociation, are within experimental error of the predictions of both ab initio calculations and of previous measurements of the polarization of the halide cofragments. The experimental and ab initio theoretical values of the Re[a(1)(1)(parallel, perpendicular)] parameter show some disagreement, suggesting that further theoretical investigations are required. Overall, good agreement occurs despite the fact that the current experiments photodissociate molecules at 295 K, whereas previous measurements were conducted at rotational temperatures of about 15 K.

  3. Five different colours solid-state fluorescence of azastilbenes: a new ...

    Indian Academy of Sciences (India)

    Moreover, liquid-state fluorescence performed in non-polar solvent in order to investigate the effect of dipolar intermolecular interactions on their fluorescence properties, the results revealed that the emission spectra of 1−5 in liquid state are similar to those of solid state, indicating that no significant dipolar interactions.

  4. Airborne Laser Polarization Sensor

    Science.gov (United States)

    Kalshoven, James, Jr.; Dabney, Philip

    1991-01-01

    Instrument measures polarization characteristics of Earth at three wavelengths. Airborne Laser Polarization Sensor (ALPS) measures optical polarization characteristics of land surface. Designed to be flown at altitudes of approximately 300 m to minimize any polarizing or depolarizing effects of intervening atmosphere and to look along nadir to minimize any effects depending on look angle. Data from measurements used in conjunction with data from ground surveys and aircraft-mounted video recorders to refine mathematical models used in interpretation of higher-altitude polarimetric measurements of reflected sunlight.

  5. Polarization at SLC

    International Nuclear Information System (INIS)

    Swartz, M.L.

    1988-07-01

    The SLAC Linear Collider has been designed to readily accommodate polarized electron beams. Considerable effort has been made to implement a polarized source, a spin rotation system, and a system to monitor the beam polarization. Nearly all major components have been fabricated. At the current time, several source and polarimeter components have been installed. The installation and commissioning of the entire system will take place during available machine shutdown periods as the commissioning of SLC progresses. It is expected that a beam polarization of 45% will be achieved with no loss in luminosity. 13 refs., 15 figs

  6. Fluorescent minerals, a review

    Science.gov (United States)

    Modreski, P.J.; Aumente-Modreski, R.

    1996-01-01

    Fluorescent minerals are more than just an attractive novelty, and collecting them is a speciality for thousands of individuals who appreciate their beauty, rarity, and scientific value. Fluorescent properties can be used as an aid to mineral identification, locality determination, and distinction between natural and synthetic gemstones. This article gives an overview of those aspects of fluorescence that are of most interest to collectors, hobbyists, and mineralogists. -from Authors

  7. TRANES analysis of the fluorescence of nile red in organized ...

    Indian Academy of Sciences (India)

    Unknown

    TRANES; TRES; fluorescence; nile red; solvent relaxation; organized molecular assemblies; solvation ... A polarity- and viscosity-sensitive dye such as nile red is used to probe the environmental properties around the site of .... Both the species are simultaneously excited giving rise to two emissive species A* and B*. A and ...

  8. Fluorescence studies on radiation oxidative damage to membranes ...

    Indian Academy of Sciences (India)

    Unknown

    plasma membrane permeability of thymocytes were monitored by fluorescein diacetate (FDA) and induced intracellular ... polarization has been shown to monitor radiation-induced structural and organizational changes in cell membrane9,11,12 ... fluorescence due to self-quenching. However, after irradiation, leakage of CF ...

  9. Time-resolved fluorescence analysis of the mobile flavin cofactor

    Indian Academy of Sciences (India)

    Conformational heterogeneity of the FAD cofactor in -hydroxybenzoate hydroxylase (PHBH) was investigated with time-resolved polarized flavin fluorescence. For binary enzyme/substrate (analogue) complexes of wild-type PHBH and Tyr222 mutants, crystallographic studies have revealed two distinct flavin conformations ...

  10. Angle-resolved polarimetry of antenna-mediated fluorescence

    NARCIS (Netherlands)

    Mohtashami, A.; Osorio, C.I.; Koenderink, A.F.

    2015-01-01

    Optical phase-array antennas can be used to control not only the angular distribution but also the polarization of fluorescence from quantum emitters. The emission pattern of the resulting system is determined by the properties of the antenna, the properties of the emitters, and the strength of the

  11. Phosphate Favors the Biosynthesis of CdS Quantum Dots inAcidithiobacillus thiooxidansATCC 19703 by Improving Metal Uptake and Tolerance.

    Science.gov (United States)

    Ulloa, Giovanni; Quezada, Carolina P; Araneda, Mabel; Escobar, Blanca; Fuentes, Edwar; Álvarez, Sergio A; Castro, Matías; Bruna, Nicolás; Espinoza-González, Rodrigo; Bravo, Denisse; Pérez-Donoso, José M

    2018-01-01

    Recently, we reported the production of Cadmium sulfide (CdS) fluorescent semiconductor nanoparticles (quantum dots, QDs) by acidophilic bacteria of the Acidithiobacillus genus. Here, we report that the addition of inorganic phosphate to Acidithiobacillus thiooxidans ATCC 19703 cultures favors the biosynthesis of CdS QDs at acidic conditions (pH 3.5). The effect of pH, phosphate and cadmium concentrations on QDs biosynthesis was studied by using Response Surface Methodology (RSM), a multivariate technique for analytical optimization scarcely used in microbiological studies to date. To address how phosphate affects intracellular biosynthesis of CdS QDs, the effect of inorganic phosphate on bacterial cadmium-uptake was evaluated. By measuring intracellular levels of cadmium we determined that phosphate influences the capacity of cells to incorporate this metal. A relation between cadmium tolerance and phosphate concentrations was also determined, suggesting that phosphate participates in the adaptation of bacteria to toxic levels of this metal. In addition, QDs-biosynthesis was also favored by the degradation of intracellular polyphosphates. Altogether, our results indicate that phosphate contributes to A. thiooxidans CdS QDs biosynthesis by influencing cadmium uptake and cadmium tolerance. These QDs may also be acting as a nucleation point for QDs formation at acidic pH. This is the first study reporting the effect of phosphates on QDs biosynthesis and describes a new cadmium-response pathway present in A. thiooxidans and most probably in other bacterial species.

  12. Phosphate Favors the Biosynthesis of CdS Quantum Dots in Acidithiobacillus thiooxidans ATCC 19703 by Improving Metal Uptake and Tolerance

    Science.gov (United States)

    Ulloa, Giovanni; Quezada, Carolina P.; Araneda, Mabel; Escobar, Blanca; Fuentes, Edwar; Álvarez, Sergio A.; Castro, Matías; Bruna, Nicolás; Espinoza-González, Rodrigo; Bravo, Denisse; Pérez-Donoso, José M.

    2018-01-01

    Recently, we reported the production of Cadmium sulfide (CdS) fluorescent semiconductor nanoparticles (quantum dots, QDs) by acidophilic bacteria of the Acidithiobacillus genus. Here, we report that the addition of inorganic phosphate to Acidithiobacillus thiooxidans ATCC 19703 cultures favors the biosynthesis of CdS QDs at acidic conditions (pH 3.5). The effect of pH, phosphate and cadmium concentrations on QDs biosynthesis was studied by using Response Surface Methodology (RSM), a multivariate technique for analytical optimization scarcely used in microbiological studies to date. To address how phosphate affects intracellular biosynthesis of CdS QDs, the effect of inorganic phosphate on bacterial cadmium-uptake was evaluated. By measuring intracellular levels of cadmium we determined that phosphate influences the capacity of cells to incorporate this metal. A relation between cadmium tolerance and phosphate concentrations was also determined, suggesting that phosphate participates in the adaptation of bacteria to toxic levels of this metal. In addition, QDs-biosynthesis was also favored by the degradation of intracellular polyphosphates. Altogether, our results indicate that phosphate contributes to A. thiooxidans CdS QDs biosynthesis by influencing cadmium uptake and cadmium tolerance. These QDs may also be acting as a nucleation point for QDs formation at acidic pH. This is the first study reporting the effect of phosphates on QDs biosynthesis and describes a new cadmium-response pathway present in A. thiooxidans and most probably in other bacterial species. PMID:29515535

  13. Phosphate Favors the Biosynthesis of CdS Quantum Dots in Acidithiobacillus thiooxidans ATCC 19703 by Improving Metal Uptake and Tolerance

    Directory of Open Access Journals (Sweden)

    Giovanni Ulloa

    2018-02-01

    Full Text Available Recently, we reported the production of Cadmium sulfide (CdS fluorescent semiconductor nanoparticles (quantum dots, QDs by acidophilic bacteria of the Acidithiobacillus genus. Here, we report that the addition of inorganic phosphate to Acidithiobacillus thiooxidans ATCC 19703 cultures favors the biosynthesis of CdS QDs at acidic conditions (pH 3.5. The effect of pH, phosphate and cadmium concentrations on QDs biosynthesis was studied by using Response Surface Methodology (RSM, a multivariate technique for analytical optimization scarcely used in microbiological studies to date. To address how phosphate affects intracellular biosynthesis of CdS QDs, the effect of inorganic phosphate on bacterial cadmium-uptake was evaluated. By measuring intracellular levels of cadmium we determined that phosphate influences the capacity of cells to incorporate this metal. A relation between cadmium tolerance and phosphate concentrations was also determined, suggesting that phosphate participates in the adaptation of bacteria to toxic levels of this metal. In addition, QDs-biosynthesis was also favored by the degradation of intracellular polyphosphates. Altogether, our results indicate that phosphate contributes to A. thiooxidans CdS QDs biosynthesis by influencing cadmium uptake and cadmium tolerance. These QDs may also be acting as a nucleation point for QDs formation at acidic pH. This is the first study reporting the effect of phosphates on QDs biosynthesis and describes a new cadmium-response pathway present in A. thiooxidans and most probably in other bacterial species.

  14. Atomic-fluorescence spectrophotometry

    International Nuclear Information System (INIS)

    Bakhturova, N.F.; Yudelevich, I.G.

    1975-01-01

    Atomic-fluorescence spectrophotometry, a comparatively new method for the analysis of trace quantities, has developed rapidly in the past ten years. Theoretical and experimental studies by many workers have shown that atomic-fluorescence spectrophotometry (AFS) is capable of achieving a better limit than atomic absorption for a large number of elements. The present review examines briefly the principles of atomic-fluorescence spectrophotometry and the types of fluorescent transition. The excitation sources, flame and nonflame atomizers, used in AFS are described. The limits of detection achieved up to the present, using flame and nonflame methods of atomization are given

  15. Optimization of conditions for cadmium selenide quantum dot biosynthesis in Saccharomyces cerevisiae.

    Science.gov (United States)

    Brooks, Jordan; Lefebvre, Daniel D

    2017-04-01

    The biosynthesis of quantum dots has been explored as an alternative to traditional physicochemical methods; however, relatively few studies have determined optimal synthesis parameters. Saccharomyces cerevisiae sequentially treated with sodium selenite and cadmium chloride synthesized CdSe quantum dots in the cytoplasm. These nanoparticles displayed a prominent yellow fluorescence, with an emission maximum of approximately 540 nm. The requirement for glutathione in the biosynthetic mechanism was explored by depleting its intracellular content through cellular treatments with 1-chloro-2,4-dinitrobenzene and buthionine sulfoximine. Synthesis was significantly inhibited by both of these reagents when they were applied after selenite treatment prior to the addition of cadmium, thereby indicating that glutathione contributes to the biosynthetic process. Determining the optimum conditions for biosynthesis revealed that quantum dots were produced most efficiently at entry into stationary phase followed by direct addition of 1 mM selenite for only 6 h and then immediately incubating these cells in fresh growth medium containing 3 mM Cd (II). Synthesis of quantum dots reached a maximum at 84 h of reaction time. Biosynthesis of 800-μg g -1 fresh weight cells was achieved. For the first time, significant efforts have been undertaken to optimize each aspect of the CdSe biosynthetic procedure in S. cerevisiae, resulting in a 70% increased production.

  16. Where does N(ε-trimethyllysine for the carnitine biosynthesis in mammals come from?

    Directory of Open Access Journals (Sweden)

    Luigi Servillo

    Full Text Available N(ε-trimethyllysine (TML is a non-protein amino acid which takes part in the biosynthesis of carnitine. In mammals, the breakdown of endogenous proteins containing TML residues is recognized as starting point for the carnitine biosynthesis. Here, we document that one of the main sources of TML could be the vegetables which represent an important part of daily alimentation for most mammals. A HPLC-ESI-MS/MS method, which we previously developed for the analysis of N(G-methylarginines, was utilized to quantitate TML in numerous vegetables. We report that TML, believed to be rather rare in plants as free amino acid, is, instead, ubiquitous in them and at not negligible levels. The occurrence of TML has been also confirmed in some vegetables by a HPLC method with fluorescence detection. Our results establish that TML can be introduced as free amino acid in conspicuous amounts from vegetables. The current opinion is that mammals utilize the breakdown of their endogenous proteins containing TML residues as starting point for carnitine biosynthesis. However, our finding raises the question of whether a tortuous and energy expensive route as the one of TML formation from the breakdown of endogenous proteins is really preferred when the substance is so easily available in vegetable foods. On the basis of this result, it must be taken into account that in mammals TML might be mainly introduced by diet. However, when the alimentary intake becomes insufficient, as during starvation, it might be supplied by endogenous protein breakdown.

  17. RHIC Polarized proton operation

    International Nuclear Information System (INIS)

    Huang, H.; Ahrens, L.; Alekseev, I.G.; Aschenauer, E.; Atoian, G.; Bai, M.; Bazilevsky, A.; Blaskiewicz, M.; Brennan, J.M.; Brown, K.A.; Bruno, D.; Connolly, R.; Dion, A.; D'Ottavio, T.; Drees, K.A.; Fischer, W.; Gardner, C.; Glenn, J.W.; Gu, X.; Harvey, M.; Hayes, T.; Hoff, L.; Hulsart, R.L.; Laster, J.; Liu, C.; Luo, Y.; MacKay, W.W.; Makdisi, Y.; Marr, G.J.; Marusic, A.; Meot, F.; Mernick, K.; Michnoff, R.; Minty, M.; Montag, C.; Morris, J.; Nemesure, S.; Poblaguev, A.; Ptitsyn, V.; Ranjibar, V.; Robert-Demolaize, G.; Roser, T.; Schmidke, B.; Schoefer, V.; Severino, F.; Smirnov, D.; Smith, K.; Steski, D.; Svirida, D.; Tepikian, S.; Trbojevic, D.; Tsoupas, N.; Tuozzolo, J.E.; Wang, G.; Wilinski, M.; Yip, K.; Zaltsman, A.; Zelenski, A.; Zeno, K.; Zhang, S.Y.

    2011-01-01

    The Relativistic Heavy Ion Collider (RHIC) operation as the polarized proton collider presents unique challenges since both luminosity(L) and spin polarization(P) are important. With longitudinally polarized beams at the experiments, the figure of merit is LP 4 . A lot of upgrades and modifications have been made since last polarized proton operation. A 9 MHz rf system is installed to improve longitudinal match at injection and to increase luminosity. The beam dump was upgraded to increase bunch intensity. A vertical survey of RHIC was performed before the run to get better magnet alignment. The orbit control is also improved this year. Additional efforts are put in to improve source polarization and AGS polarization transfer efficiency. To preserve polarization on the ramp, a new working point is chosen such that the vertical tune is near a third order resonance. The overview of the changes and the operation results are presented in this paper. Siberian snakes are essential tools to preserve polarization when accelerating polarized beams to higher energy. At the same time, the higher order resonances still can cause polarization loss. As seen in RHIC, the betatron tune has to be carefully set and maintained on the ramp and during the store to avoid polarization loss. In addition, the orbit control is also critical to preserve polarization. The higher polarization during this run comes from several improvements over last run. First we have a much better orbit on the ramp. The orbit feedback brings down the vertical rms orbit error to 0.1mm, much better than the 0.5mm last run. With correct BPM offset and vertical realignment, this rms orbit error is indeed small. Second, the jump quads in the AGS improved input polarization for RHIC. Third, the vertical tune was pushed further away from 7/10 snake resonance. The tune feedback maintained the tune at the desired value through the ramp. To calibrate the analyzing power of RHIC polarimeters at any energy above

  18. RHIC Polarized proton operation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, H.; Ahrens, L.; Alekseev, I.G.; Aschenauer, E.; Atoian, G.; Bai, M.; Bazilevsky, A.; Blaskiewicz, M.; Brennan, J.M.; Brown, K.A.; Bruno, D.; Connolly, R.; Dion, A.; D' Ottavio, T.; Drees, K.A.; Fischer, W.; Gardner, C.; Glenn, J.W.; Gu, X.; Harvey, M.; Hayes, T.; Hoff, L.; Hulsart, R.L.; Laster, J.; Liu, C.; Luo, Y.; MacKay, W.W.; Makdisi, Y.; Marr, G.J.; Marusic, A.; Meot, F.; Mernick, K.; Michnoff, R,; Minty, M.; Montag, C.; Morris, J.; Nemesure, S.; Poblaguev, A.; Ptitsyn, V.; Ranjibar, V.; Robert-Demolaize, G.; Roser, T.; J.; Severino, F.; Schmidke, B.; Schoefer, V.; Severino, F.; Smirnov, D.; Smith, K.; Steski, D.; Svirida, D.; Tepikian, S.; Trbojevic, D.; Tsoupas, N.; Tuozzolo, J. Wang, G.; Wilinski, M.; Yip, K.; Zaltsman, A.; Zelenski, A.; Zeno, K.; Zhang, S.Y.

    2011-03-28

    The Relativistic Heavy Ion Collider (RHIC) operation as the polarized proton collider presents unique challenges since both luminosity(L) and spin polarization(P) are important. With longitudinally polarized beams at the experiments, the figure of merit is LP{sup 4}. A lot of upgrades and modifications have been made since last polarized proton operation. A 9 MHz rf system is installed to improve longitudinal match at injection and to increase luminosity. The beam dump was upgraded to increase bunch intensity. A vertical survey of RHIC was performed before the run to get better magnet alignment. The orbit control is also improved this year. Additional efforts are put in to improve source polarization and AGS polarization transfer efficiency. To preserve polarization on the ramp, a new working point is chosen such that the vertical tune is near a third order resonance. The overview of the changes and the operation results are presented in this paper. Siberian snakes are essential tools to preserve polarization when accelerating polarized beams to higher energy. At the same time, the higher order resonances still can cause polarization loss. As seen in RHIC, the betatron tune has to be carefully set and maintained on the ramp and during the store to avoid polarization loss. In addition, the orbit control is also critical to preserve polarization. The higher polarization during this run comes from several improvements over last run. First we have a much better orbit on the ramp. The orbit feedback brings down the vertical rms orbit error to 0.1mm, much better than the 0.5mm last run. With correct BPM offset and vertical realignment, this rms orbit error is indeed small. Second, the jump quads in the AGS improved input polarization for RHIC. Third, the vertical tune was pushed further away from 7/10 snake resonance. The tune feedback maintained the tune at the desired value through the ramp. To calibrate the analyzing power of RHIC polarimeters at any energy above

  19. Our Polar Past

    Science.gov (United States)

    Clary, Renee; Wandersee, James

    2009-01-01

    The study of polar exploration is fascinating and offers students insights into the history, culture, and politics that affect the developing sciences at the farthest ends of Earth. Therefore, the authors think there is value in incorporating polar exploration accounts within modern science classrooms, and so they conducted research to test their…

  20. Terahertz polarization imaging

    NARCIS (Netherlands)

    Van der Valk, N.C.J.; Van der Marel, W.A.M.; Planken, P.C.M.

    2005-01-01

    We present a new method to measure the polarization state of a terahertz pulse by using a modified electrooptic sampling setup. To illustrate the power of this method, we show two examples in which the knowledge of the polarization of the terahertz pulse is essential for interpreting the results:

  1. Polarized proton beams

    International Nuclear Information System (INIS)

    Roser, T.

    1995-01-01

    The acceleration of polarized proton beams in circular accelerators is complicated by the presence of numerous depolarizing spin resonances. Careful and tedious minimization of polarization loss at each of these resonances allowed acceleration of polarized proton beams up to 22 GeV. It has been the hope that Siberian Snakes, which are local spin rotators inserted into ring accelerators, would eliminate these resonances and allow acceleration of polarized beams with the same ease and efficiency that is now routine for unpolarized beams. First tests at IUCF with a full Siberian Snake showed that the spin dynamics with a Snake can be understood in detail. The author now has results of the first tests of a partial Siberian Snake at the AGS, accelerating polarized protons to an energy of about 25 GeV. These successful tests of storage and acceleration of polarized proton beams open up new possibilities such as stored polarized beams for internal target experiments and high energy polarized proton colliders

  2. Polar Science Is Cool!

    Science.gov (United States)

    Weeks, Sophie

    2012-01-01

    Children are fascinated by the fact that polar scientists do research in extremely cold and dangerous places. In the Arctic they might be viewed as lunch by a polar bear. In the Antarctic, they could lose toes and fingers to frostbite and the wind is so fast it can rip skin off. They camp on ice in continuous daylight, weeks from any form of…

  3. Precision Polarization of Neutrons

    Science.gov (United States)

    Martin, Elise; Barron-Palos, Libertad; Couture, Aaron; Crawford, Christopher; Chupp, Tim; Danagoulian, Areg; Estes, Mary; Hona, Binita; Jones, Gordon; Klein, Andi; Penttila, Seppo; Sharma, Monisha; Wilburn, Scott

    2009-05-01

    Determining polarization of a cold neutron beam to high precision is required for the next generation neutron decay correlation experiments at the SNS, such as the proposed abBA and PANDA experiments. Precision polarimetry measurements were conducted at Los Alamos National Laboratory with the goal of determining the beam polarization to the level of 10-3 or better. The cold neutrons from FP12 were polarized using optically polarized ^3He gas as a spin filter, which has a highly spin-dependent absorption cross section. A second ^ 3He spin filter was used to analyze the neutron polarization after passing through a resonant RF spin rotator. A discussion of the experiment and results will be given.

  4. Optically polarized 3He

    Science.gov (United States)

    Gentile, T. R.; Nacher, P. J.; Saam, B.; Walker, T. G.

    2018-01-01

    This article reviews the physics and technology of producing large quantities of highly spin-polarized 3He nuclei using spin-exchange (SEOP) and metastability-exchange (MEOP) optical pumping. Both technical developments and deeper understanding of the physical processes involved have led to substantial improvements in the capabilities of both methods. For SEOP, the use of spectrally narrowed lasers and K-Rb mixtures has substantially increased the achievable polarization and polarizing rate. For MEOP nearly lossless compression allows for rapid production of polarized 3He and operation in high magnetic fields has likewise significantly increased the pressure at which this method can be performed, and revealed new phenomena. Both methods have benefitted from development of storage methods that allow for spin-relaxation times of hundreds of hours, and specialized precision methods for polarimetry. SEOP and MEOP are now widely applied for spin-polarized targets, neutron spin filters, magnetic resonance imaging, and precision measurements. PMID:29503479

  5. Optically polarized 3He

    Science.gov (United States)

    Gentile, T. R.; Nacher, P. J.; Saam, B.; Walker, T. G.

    2017-10-01

    This article reviews the physics and technology of producing large quantities of highly spin-polarized 3He nuclei using spin-exchange (SEOP) and metastability-exchange (MEOP) optical pumping. Both technical developments and deeper understanding of the physical processes involved have led to substantial improvements in the capabilities of both methods. For SEOP, the use of spectrally narrowed lasers and K-Rb mixtures has substantially increased the achievable polarization and polarizing rate. For MEOP nearly lossless compression allows for rapid production of polarized 3He and operation in high magnetic fields has likewise significantly increased the pressure at which this method can be performed, and revealed new phenomena. Both methods have benefitted from development of storage methods that allow for spin-relaxation times of hundreds of hours, and specialized precision methods for polarimetry. SEOP and MEOP are now widely applied for spin-polarized targets, neutron spin filters, magnetic resonance imaging, and precision measurements.

  6. Parallel Polarization State Generation.

    Science.gov (United States)

    She, Alan; Capasso, Federico

    2016-05-17

    The control of polarization, an essential property of light, is of wide scientific and technological interest. The general problem of generating arbitrary time-varying states of polarization (SOP) has always been mathematically formulated by a series of linear transformations, i.e. a product of matrices, imposing a serial architecture. Here we show a parallel architecture described by a sum of matrices. The theory is experimentally demonstrated by modulating spatially-separated polarization components of a laser using a digital micromirror device that are subsequently beam combined. This method greatly expands the parameter space for engineering devices that control polarization. Consequently, performance characteristics, such as speed, stability, and spectral range, are entirely dictated by the technologies of optical intensity modulation, including absorption, reflection, emission, and scattering. This opens up important prospects for polarization state generation (PSG) with unique performance characteristics with applications in spectroscopic ellipsometry, spectropolarimetry, communications, imaging, and security.

  7. Relaxation dynamics of a polar solvent cage around a nonpolar electronically excited solvent probe. A subpicosecond laser study

    International Nuclear Information System (INIS)

    Mialocq, J.C.; Hebert, P.; Baldacchino, G.; Gustavsson, T.

    1993-01-01

    The aim of the present paper is to show that the LDS 751 unsymmetrical cyanine laser dye, highly polar in the ground state and non polar in the fluorescent excited singlet state, is a suitable solvent probe. Excitation of LDS 751 in a polar solvent with an ultrashort laser pulse suddenly annihilates the permanent dipole moment of the solute and suppresses the forces which orientate the nearby solvent molecules. The subpicosecond analysis of the Time-Dependent Fluorescence Stokes Shift (TDFSS) of LDS 751 thus enables to probe the relaxation of polar solvent molecules which can be considered as free of solute-solvent interactions. (author)

  8. Multimodal fluorescence imaging spectroscopy

    NARCIS (Netherlands)

    Stopel, Martijn H W; Blum, Christian; Subramaniam, Vinod; Engelborghs, Yves; Visser, Anthonie J.W.G.

    2014-01-01

    Multimodal fluorescence imaging is a versatile method that has a wide application range from biological studies to materials science. Typical observables in multimodal fluorescence imaging are intensity, lifetime, excitation, and emission spectra which are recorded at chosen locations at the sample.

  9. Fluorescence live cell imaging.

    Science.gov (United States)

    Ettinger, Andreas; Wittmann, Torsten

    2014-01-01

    Fluorescence microscopy of live cells has become an integral part of modern cell biology. Fluorescent protein (FP) tags, live cell dyes, and other methods to fluorescently label proteins of interest provide a range of tools to investigate virtually any cellular process under the microscope. The two main experimental challenges in collecting meaningful live cell microscopy data are to minimize photodamage while retaining a useful signal-to-noise ratio and to provide a suitable environment for cells or tissues to replicate physiological cell dynamics. This chapter aims to give a general overview on microscope design choices critical for fluorescence live cell imaging that apply to most fluorescence microscopy modalities and on environmental control with a focus on mammalian tissue culture cells. In addition, we provide guidance on how to design and evaluate FP constructs by spinning disk confocal microscopy. © 2014 Elsevier Inc. All rights reserved.

  10. Fluorescence Decay Dynamics of Ethidium Bromide in Polymers

    International Nuclear Information System (INIS)

    Jee, Ah Young; Min Yung

    2010-01-01

    The fluorescence lifetimes of EB in five polymers covering LDPE, HDPE, PC, PS, and PAA were measured by picosecond time-correlated single photon counting. The lifetime change of EB has been previously described by hydrogen bonding ability. In this work, we have observed that the lifetime of EB depends strongly on the Young's modulus of medium. Thus, it is possible that the fluorescence decay dynamics of EB could be influenced by medium rigidity rather than hydrogen bonding ability in polymer. The medium influence on the fluorescence decay dynamics of ethidium bromide (EB) has been investigated in various environments. For example, Ohmstead and Kearns related the fluorescence lifetime of EB to the excited-state proton transfer process. In addition, they reported that the solvent viscosity plays a minor role in the excited state decay process of EB. Chirico et al. measured the fluorescence decay of EB as 1.7 ns in water and 6.5 ns in ethanol and concluded that hydrogen bonding ability is a key factor for the nonradiative relaxation. Pal et al. measured the fluorescence decay time of EB in acetone, acetonitrile, and their mixtures. They observed that the fluorescence decay processes were independent on the solvent polarity. These results show that the EB lifetime does not depend much on polarity or viscosity, but is mainly influenced by hydrogen bonding. Overall, EB is one of most widely used dyes for probing DNA. When EB is intercalated into the helical structure of DNA, a large increase in the fluorescence lifetime has been observed in comparison with water environment, and the fluorescence enhancement was attributed to the blocking of the excited-state proton transfer

  11. Combinatorial Biosynthesis – Potential and Problems

    Science.gov (United States)

    Floss, Heinz G.

    2007-01-01

    Because of their ecological functions, natural products have been optimized in evolution for interaction with biological systems and receptors. However, they have not necessarily been optimized for other desirable drug properties and thus can often be improved by structural modification. Using examples from the literature, this paper reviews the opportunities for increasing structural diversity among natural products by combinatorial biosynthesis, i.e., the genetic manipulation of biosynthetic pathways. It distinguishes between combinatorial biosynthesis in a narrower sense to generate libraries of modified structures, and metabolic engineering for the targeted formation of specific structural analogs. Some of the problems and limitations encountered with these approaches are also discussed. Work from the author’s laboratory on ansamycin antibiotics is presented which illustrates some of the opportunities and limitations. PMID:16414140

  12. Combinatorial biosynthesis of polyketides--a perspective.

    Science.gov (United States)

    Wong, Fong T; Khosla, Chaitan

    2012-04-01

    Since their discovery, polyketide synthases have been attractive targets of biosynthetic engineering to make 'unnatural' natural products. Although combinatorial biosynthesis has made encouraging advances over the past two decades, the field remains in its infancy. In this enzyme-centric perspective, we discuss the scientific and technological challenges that could accelerate the adoption of combinatorial biosynthesis as a method of choice for the preparation of encoded libraries of bioactive small molecules. Borrowing a page from the protein structure prediction community, we propose a periodic challenge program to vet the most promising methods in the field, and to foster the collective development of useful tools and algorithms. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Structural basis for phosphatidylinositol-phosphate biosynthesis

    Science.gov (United States)

    Clarke, Oliver B.; Tomasek, David; Jorge, Carla D.; Dufrisne, Meagan Belcher; Kim, Minah; Banerjee, Surajit; Rajashankar, Kanagalaghatta R.; Shapiro, Lawrence; Hendrickson, Wayne A.; Santos, Helena; Mancia, Filippo

    2015-10-01

    Phosphatidylinositol is critical for intracellular signalling and anchoring of carbohydrates and proteins to outer cellular membranes. The defining step in phosphatidylinositol biosynthesis is catalysed by CDP-alcohol phosphotransferases, transmembrane enzymes that use CDP-diacylglycerol as donor substrate for this reaction, and either inositol in eukaryotes or inositol phosphate in prokaryotes as the acceptor alcohol. Here we report the structures of a related enzyme, the phosphatidylinositol-phosphate synthase from Renibacterium salmoninarum, with and without bound CDP-diacylglycerol to 3.6 and 2.5 Å resolution, respectively. These structures reveal the location of the acceptor site, and the molecular determinants of substrate specificity and catalysis. Functional characterization of the 40%-identical ortholog from Mycobacterium tuberculosis, a potential target for the development of novel anti-tuberculosis drugs, supports the proposed mechanism of substrate binding and catalysis. This work therefore provides a structural and functional framework to understand the mechanism of phosphatidylinositol-phosphate biosynthesis.

  14. Occurrence and biosynthesis of carotenoids in phytoplankton.

    Science.gov (United States)

    Huang, Jim Junhui; Lin, Shaoling; Xu, Wenwen; Cheung, Peter Chi Keung

    2017-09-01

    Naturally occurring carotenoids are important sources of antioxidants, anti-cancer compounds and anti-inflammatory agents and there is thus considerable market demand for their pharmaceutical applications. Carotenoids are widely distributed in marine and freshwater organisms including microalgae, phytoplankton, crustaceans and fish, as well as in terrestrial plants and birds. Recently, phytoplankton-derived carotenoids have received much attention due to their abundance, rapid rate of biosynthesis and unique composition. The carotenoids that accumulate in particular phytoplankton phyla are synthesized by specific enzymes and play unique physiological roles. This review focuses on studies related to the occurrence of carotenoids in different phytoplankton phyla and the molecular aspects of their biosynthesis. Recent biotechnological advances in the isolation and characterization of some representative carotenoid synthases in phytoplankton are also discussed. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. A cutin fluorescence pattern in developing embryos of some angiosperms

    Directory of Open Access Journals (Sweden)

    Ewa Szczuka

    2014-01-01

    Full Text Available A cuticle visualized by auramine O fluorescence appears on the developing embryos of 9 species belonging to Cruciferae, Caryophyllaceae, Plantaginaceae, Linaceae and Papilionaceae. In the investigated species the formation and extent of fluorescing and non-fluorescing embryonic areas follow a similar pattern. At first the cutin fluorescing layer is formed on the apical part of the proembryo without delimited protoderm. This layer extends and at the late globular stage envelops the embryo proper, except for a cell adjoining the suspensor. Fluorescing cutin persists during the heart stage but disappears from the torpedo embryo. During these stages there is no cutine fluorescence on suspensorial cells. Continuous cutin fluorescence appears again on the surface of the whole embryo by the late torpedo stage. Then fluorescence disappears from the radicular part of U-shaped embryos, but persists on the shoot apex, cotyledons and at least on the upper part of hypocotyl. It is assumed that polarization and nutrition of the embryo may be influenced by cuticular changes.

  16. Optical characterization and polarization calibration for rigid endoscopes

    Science.gov (United States)

    Garcia, Missael; Gruev, Viktor

    2017-02-01

    Polarization measurements give orthogonal information to spectral images making them a great tool in the characterization of environmental parameters in nature. Thus, polarization imagery has proven to be remarkably useful in a vast range of biomedical applications. One such application is the early diagnosis of flat cancerous lesions in murine colorectal tumor models, where polarization data complements NIR fluorescence analysis. Advances in nanotechnology have led to compact and precise bio-inspired imaging sensors capable of accurately co-registering multidimensional spectral and polarization information. As more applications emerge for these imagers, the optics used in these instruments get very complex and can potentially compromise the original polarization state of the incident light. Here we present a complete optical and polarization characterization of three rigid endoscopes of size 1.9mm x 10cm (Karl Storz, Germany), 5mm x 30cm, and 10mm x 33cm (Olympus, Germany), used in colonoscopy for the prevention of colitis-associated cancer. Characterization results show that the telescope optics act as retarders and effectively depolarize the linear component. These incorrect readings can cause false-positives or false-negatives leading to an improper diagnosis. In this paper, we offer a polarization calibration scheme for these endoscopes based on Mueller calculus. By modeling the optical properties from training data as real-valued Mueller matrices, we are able to successfully reconstruct the initial polarization state acquired by the imaging system.

  17. Microbial biosynthesis of nontoxic gold nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Swarup, E-mail: swaruproy@klyuniv.ac.in [Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal (India); Das, Tapan Kumar [Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal (India); Maiti, Guru Prasad [Department of Molecular Biology and Biotechnology, University of Kalyani, Kalyani 741235, West Bengal (India); Department of Anesthesiology, Texas Tech University Health science Center, 3601 4th Street, Lubbock, TX 79430 (United States); Basu, Utpal [Department of Molecular Biology and Biotechnology, University of Kalyani, Kalyani 741235, West Bengal (India)

    2016-01-15

    Graphical abstract: The manuscript deals with the fungus mediated optimized biologically synthesized GNPs using Aspergillus foetidus and characterization of biosynthesized GNPs using various physico-chemical methods. The fairly stable synthesized nanoparticles have size in the range of 10–40 nm. Cytotoxicity study of biosynthesized GNPs on Human lung cancer cell line A549 showed no significant toxicity of GNPs. - Highlights: • A novel biosynthesis process of GNPs using Aspergillus foetidus. • Biosynthesized GNPs are in the range of 10–40 nm as observed from TEM. • This process of synthesis is an optimized biosynthesis process of GNPs. • Biosynthesized GNPs are noncytotoxic against A549 cell line. - Abstract: We study the extracellular biosynthesis of gold nanoparticles (GNPs) using the fungal species Aspergillus foetidus. The formation of GNPs were initially monitored by visual observation and then characterized with the help of various characterization techniques. X-ray diffraction (XRD) results revealed distinctive formation of face centered cubic crystalline GNPs. From field emission scanning electron microscopy (FESEM) the morphology of the nanoparticles were found to be roughly spherical and within the size range of 30–50 nm. The spherical and polydispersed GNPs in the range of 10–40 nm were observed by transmission electron microscopy (TEM) analysis. It was established that alkaline pH, 1 mM gold salt concentration and 75 °C temperature were the respective optimum parameter for biosynthesis of GNPs. Cell cytotoxicity of GNP was compared with that of normal gold salt solution on A549 cell. The A549 cell growth in presence of GNPs was found to be comparatively less toxic than the gold ion.

  18. Microbial biosynthesis of nontoxic gold nanoparticles

    International Nuclear Information System (INIS)

    Roy, Swarup; Das, Tapan Kumar; Maiti, Guru Prasad; Basu, Utpal

    2016-01-01

    Graphical abstract: The manuscript deals with the fungus mediated optimized biologically synthesized GNPs using Aspergillus foetidus and characterization of biosynthesized GNPs using various physico-chemical methods. The fairly stable synthesized nanoparticles have size in the range of 10–40 nm. Cytotoxicity study of biosynthesized GNPs on Human lung cancer cell line A549 showed no significant toxicity of GNPs. - Highlights: • A novel biosynthesis process of GNPs using Aspergillus foetidus. • Biosynthesized GNPs are in the range of 10–40 nm as observed from TEM. • This process of synthesis is an optimized biosynthesis process of GNPs. • Biosynthesized GNPs are noncytotoxic against A549 cell line. - Abstract: We study the extracellular biosynthesis of gold nanoparticles (GNPs) using the fungal species Aspergillus foetidus. The formation of GNPs were initially monitored by visual observation and then characterized with the help of various characterization techniques. X-ray diffraction (XRD) results revealed distinctive formation of face centered cubic crystalline GNPs. From field emission scanning electron microscopy (FESEM) the morphology of the nanoparticles were found to be roughly spherical and within the size range of 30–50 nm. The spherical and polydispersed GNPs in the range of 10–40 nm were observed by transmission electron microscopy (TEM) analysis. It was established that alkaline pH, 1 mM gold salt concentration and 75 °C temperature were the respective optimum parameter for biosynthesis of GNPs. Cell cytotoxicity of GNP was compared with that of normal gold salt solution on A549 cell. The A549 cell growth in presence of GNPs was found to be comparatively less toxic than the gold ion.

  19. Polarization at the SLC

    Energy Technology Data Exchange (ETDEWEB)

    Moffeit, K.C.

    1988-10-01

    The Stanford Linear collider was designed to accommodate polarized electron beams. Longitudinally polarized electrons colliding with unpolarized positrons at a center of mass energy near the Z/sup 0/ mass can be used as novel and sensitive probes of the electroweak process. A gallium arsenide based photon emission source will provide a beam of longitudinally polarized electrons of about 45 percent polarization. A system of bend magnets and a superconducting solenoid will be used to rotate the spins so that the polarization is preserved while the 1.21 GeV electrons are stored in the damping ring. Another set of bend magnets and two superconducting solenoids orient the spin vectors so that longitudinal polarization of the electrons is achieved at the collision point with the unpolarized positrons. A system to monitor the polarization based on Moller and Compton scattering will be used. Nearly all major components have been fabricated and tested. Subsystems of the source and polarimeters have been installed, and studies are in progress. The installation and commissioning of the entire system will take place during available machine shutdown periods as the commissioning of SLC progresses. 8 refs., 16 figs., 1 tab.

  20. Tetrahydrobiopterin biosynthesis, utilization and pharmacological effects.

    Science.gov (United States)

    Werner-Felmayer, G; Golderer, G; Werner, E R

    2002-04-01

    Tetrahydrobiopterin (H4-biopterin) is an essential cofactor of a set of enzymes that are of central metabolic importance, i.e. the hydroxylases of the three aromatic amino acids phenylalanine, tyrosine, and tryptophan, of ether lipid oxidase, and of the three nitric oxide synthase (NOS) isoenzymes. As a consequence, H4-biopterin plays a key role in a vast number of biological processes and pathological states associated with neurotransmitter formation, vasorelaxation, and immune response. In mammals, its biosynthesis is controlled by hormones, cytokines and certain immune stimuli. This review aims to summarize recent developments concerning regulation of H4-biopterin biosynthetic and regulatory enzymes and pharmacological effects of H4-biopterin in various conditions, e.g. endothelial dysfunction or apoptosis of neuronal cells. Also, approaches towards gene therapy of diseases like the different forms of phenylketonuria or of Parkinson's disease are reviewed. Additional emphasis is given to H4-biopterin biosynthesis and function in non-mammalian species such as fruit fly, zebra fish, fungi, slime molds, the bacterium Nocardia as well as to the parasitic protozoan genus of Leishmania that is not capable of pteridine biosynthesis but has evolved a sophisticated salvage network for scavenging various pteridine compounds, notably folate and biopterin.

  1. Exopolysaccharide biosynthesis by Lactobacillus helveticus ATCC 15807.

    Science.gov (United States)

    Torino, M I; Mozzi, F; Font de Valdez, G

    2005-08-01

    Exopolysaccharide (EPS) production and the activities of the enzymes involved in sugar nucleotide biosynthesis in Lactobacillus helveticus ATCC 15807 under controlled pH conditions were investigated. Batch fermentations using lactose as energy source showed higher EPS synthesis by L. helveticus ATCC 15807 at pH 4.5 with respect to pH 6.2, the enzyme alpha-phosphoglucomutase (alpha-PGM) being correlated with both total and specific EPS production. When glucose was used as carbon source instead of lactose, the lower EPS synthesis obtained was linked to a decrease in alpha-PGM and galactose 1-phosphate-uridyltransferase (GalT) activities, the reduction of the latter being more pronounced. Higher EPS production by L. helveticus ATCC 15807 at the acidic constant pH of 4.5 requires that both alpha-PGM and GalT activities are high. These enzymes are needed to synthesize UDP-glucose and UDP-galactose for supplying the corresponding monomers for EPS biosynthesis. Although differences are observed in EPS production by this strain regarding the energy source (lactose or glucose), the monomeric composition of the polymers produced is independent of the carbohydrate used. The obtained results contribute to a better understanding of the physiological factors that affect EPS biosynthesis by lactobacilli, which could help in the correct handling of the fermentation parameters within the fermented dairy industry.

  2. Lipopolysaccharide Structure and Biosynthesis in Helicobacter pylori.

    Science.gov (United States)

    Li, Hong; Liao, Tingting; Debowski, Aleksandra W; Tang, Hong; Nilsson, Hans-Olof; Stubbs, Keith A; Marshall, Barry J; Benghezal, Mohammed

    2016-12-01

    This review covers the current knowledge and gaps in Helicobacter pylori lipopolysaccharide (LPS) structure and biosynthesis. H. pylori is a Gram-negative bacterium which colonizes the luminal surface of the human gastric epithelium. Both a constitutive alteration of the lipid A preventing TLR4 elicitation and host mimicry of the Lewis antigen decorated O-antigen of H. pylori LPS promote immune escape and chronic infection. To date, the complete structure of H. pylori LPS is not available, and the proposed model is a linear arrangement composed of the inner core defined as the hexa-saccharide (Kdo-LD-Hep-LD-Hep-DD-Hep-Gal-Glc), the outer core composed of a conserved trisaccharide (-GlcNAc-Fuc-DD-Hep-) linked to the third heptose of the inner core, the glucan, the heptan and a variable O-antigen, generally consisting of a poly-LacNAc decorated with Lewis antigens. Although the glycosyltransferases (GTs) responsible for the biosynthesis of the H. pylori O-antigen chains have been identified and characterized, there are many gaps in regard to the biosynthesis of the core LPS. These limitations warrant additional mutagenesis and structural studies to obtain the complete LPS structure and corresponding biosynthetic pathway of this important gastric bacterium. © 2016 John Wiley & Sons Ltd.

  3. Polarized atomic beams for targets

    International Nuclear Information System (INIS)

    Grueebler, W.

    1984-01-01

    The basic principle of the production of polarized atomic hydrogen and deuterium beams are reviewed. The status of the present available polarization, density and intensity are presented. The improvement of atomic beam density by cooling the hydrogen atoms to low velocity is discussed. The possible use of polarized atomic beams as targets in storage rings is shown. It is proposed that polarized atomic beams can be used to produce polarized gas targets with high polarization and greatly improved density

  4. Polarized scintillator targets

    Science.gov (United States)

    van den Brandt, B.; Bunyatova, E. I.; Hautle, P.; Konter, J. A.; Mango, S.

    2000-05-01

    The hydrogen nuclei in an organic scintillator have been polarized to more than 80% and the deuterons in its fully deuterated version to 24%. The scintillator, doped with TEMPO, has been polarized dynamically in a field of 2.5 T in a vertical dilution refrigerator in which a plastic lightguide transports the scintillation light from the sample in the mixing chamber to a photomultiplier outside the cryostat. Sizeable solid samples with acceptable optical properties and light output have been prepared and successfully operated as "live" polarized targets in nuclear physics experiments.

  5. Polarized scintillator targets

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, B. van den E-mail: vandenbrandt@psi.ch; Bunyatova, E.I.; Hautle, P.; Konter, J.A.; Mango, S

    2000-05-21

    The hydrogen nuclei in an organic scintillator have been polarized to more than 80% and the deuterons in its fully deuterated version to 24%. The scintillator, doped with TEMPO, has been polarized dynamically in a field of 2.5 T in a vertical dilution refrigerator in which a plastic lightguide transports the scintillation light from the sample in the mixing chamber to a photomultiplier outside the cryostat. Sizeable solid samples with acceptable optical properties and light output have been prepared and successfully operated as 'live' polarized targets in nuclear physics experiments.

  6. Polarization measurement in the COMPASS polarized target

    CERN Document Server

    Kondo, K; Baum, G; Berglund, P; Doshita, N; Gautheron, F; Görtz, S; Hasegawa, T; Horikawa, N; Ishimoto, S; Iwata, T; Kisselev, Yu V; Koivuniemi, J H; Le Goff, J M; Magnon, A; Meyer, W; Reicherz, G; Matsuda, T

    2004-01-01

    Continuous wave nuclear magnetic resonance (NMR) is used to determine the target polarization in the COMPASS experiment. The system is made of the so-called Liverpool Q-meters, Yale-cards, and VME modules for data taking and system controlling. In 2001 the NMR coils were embedded in the target material, while in 2002 and 2003 the coils were mounted on the outer surface of the target cells to increase the packing factor of the material. Though the error of the measurement became larger with the outer coils than with the inner coils, we have performed stable measurements throughout the COMPASS run time for 3 years. The maximum polarization was +57% and -53% as the average in the target cells.

  7. Biosynthesis and biotransformation of bile acids

    Directory of Open Access Journals (Sweden)

    Šarenac Tanja M.

    2017-01-01

    Full Text Available Bile acids are steroidal compounds, which contain 24 carbon atoms. They can be classified into two major groups: primary and secondary. The most abundant bile acids: The primary bile acids include cholic acid and chenodeoxycholic acid, while the major secondary bile acids are deoxycholic acid and litocholic acid. Bile acids are important physiological agents for intestinal absorption of nutrients and are used for biliary lipid secretion, toxic metabolites and xenobiotics. The aim of this paper is to analyze biosynthesis and biotransformation of bile acids, as preparation for practical usage in laboratory and clinical conditions. Topic: Biosynthesis and biotransformation of bile acids: The biosynthesis of bile acids is the dominant metabolic pathway for catabolism of cholesterol in humans. The classical route of biosynthesis of bile acids is embarking on the conversion of cholesterol into 7α-hydroxycholesterol using enzyme 7α-cholesterol hydroxylase (CYP7A1. This enzyme is one of the microsomal cytochrome P450 enzyme is localized exclusively in the liver. Classical road is the main road in the biosynthesis of bile acids, and its total contribution amounts to 90% for people, and 75% in mice. CYP 7A1 enzyme is considered to be sensitive to the inhibition of carbon monoxide, and the condition for the effect of NADPH, the oxygen, lecithin, and the NADPH-cytochrome P450 reductase. Bile acids are important signaling molecules and metabolic controls which activate the nuclear receptor and the G protein-coupled receptors (GPCR, a signaling lipid regulation of the liver, glucose and energy homeostasis. Also, bile acids maintain metabolic homeostasis. Biotransformation of bile acids: The conversion of cholesterol into bile acids just important for maintenance of cholesterol homeostasis, but also to prevent the accumulation of cholesterol, triglycerides and toxic metabolites as well as violations of the liver and other organs. Enterohepatic circulation of

  8. Highly thermostable fluorescent proteins

    Science.gov (United States)

    Bradbury, Andrew M [Santa Fe, NM; Waldo, Geoffrey S [Santa Fe, NM; Kiss, Csaba [Los Alamos, NM

    2011-03-22

    Thermostable fluorescent proteins (TSFPs), methods for generating these and other stability-enhanced proteins, polynucleotides encoding such proteins, and assays and method for using the TSFPs and TSFP-encoding nucleic acid molecules are provided. The TSFPs of the invention show extremely enhanced levels of stability and thermotolerance. In one case, for example, a TSFP of the invention is so stable it can be heated to 99.degree. C. for short periods of time without denaturing, and retains 85% of its fluorescence when heated to 80.degree. C. for several minutes. The invention also provides a method for generating stability-enhanced variants of a protein, including but not limited to fluorescent proteins.

  9. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Stuhrmann, H.B. [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    1996-11-01

    Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.

  10. Time Domain Induced Polarization

    DEFF Research Database (Denmark)

    Fiandaca, Gianluca; Auken, Esben; Christiansen, Anders Vest

    2012-01-01

    Time-domain-induced polarization has significantly broadened its field of reference during the last decade, from mineral exploration to environmental geophysics, e.g., for clay and peat identification and landfill characterization. Though, insufficient modeling tools have hitherto limited the use...... of time-domaininduced polarization for wider purposes. For these reasons, a new forward code and inversion algorithm have been developed using the full-time decay of the induced polarization response, together with an accurate description of the transmitter waveform and of the receiver transfer function......%. Furthermore, the presence of low-pass filters in time-domain-induced polarization instruments affects the early times of the acquired decays (typically up to 100 ms) and has to be modeled in the forward response to avoid significant loss of resolution. The developed forward code has been implemented in a 1D...

  11. Polarized proton colliders

    International Nuclear Information System (INIS)

    Roser, T.

    1995-01-01

    High energy polarized beam collisions will open up the unique physics opportunities of studying spin effects in hard processes. This will allow the study of the spin structure of the proton and also the verification of the many well documented expectations of spin effects in perturbative QCD and parity violation in W and Z production. Proposals for polarized proton acceleration for several high energy colliders have been developed. A partial Siberian Snake in the AGS has recently been successfully tested and full Siberian Snakes, spin rotators, and polarimeters for RHIC are being developed to make the acceleration of polarized beams to 250 GeV possible. This allows for the unique possibility of colliding two 250 GeV polarized proton beams at luminosities of up to 2 x 10 32 cm -2 s -1

  12. Double-gated spectral snapshots for biomolecular fluorescence

    International Nuclear Information System (INIS)

    Nakamura, Ryosuke; Hamada, Norio; Ichida, Hideki; Tokunaga, Fumio; Kanematsu, Yasuo

    2007-01-01

    A versatile method to take femtosecond spectral snapshots of fluorescence has been developed based on a double gating technique in the combination of an optical Kerr gate and an image intensifier as an electrically driven gate set in front of a charge-coupled device detector. The application of a conventional optical-Kerr-gate method is limited to molecules with the short fluorescence lifetime up to a few hundred picoseconds, because long-lifetime fluorescence itself behaves as a source of the background signal due to insufficiency of the extinction ratio of polarizers employed for the Kerr gate. By using the image intensifier with the gate time of 200 ps, we have successfully suppressed the background signal and overcome the application limit of optical-Kerr-gate method. The system performance has been demonstrated by measuring time-resolved fluorescence spectra for laser dye solution and the riboflavin solution as a typical sample of biomolecule

  13. Plasma polarization spectroscopy

    International Nuclear Information System (INIS)

    Iwamae, Atsushi; Horimoto, Yasuhiro; Fujimoto, Takashi; Hasegawa, Noboru; Sukegawa, Kouta; Kawachi, Tetsuya

    2005-01-01

    The electron velocity distribution function (EVDF) in plasma can be anisotropic in laser-produced plasmas. We have developed a new technique to evaluate the polarization degree of the emission lines in the extreme vacuum ultra violet wavelength region. The polarization of the emission lines and the continuums from the lithium-like nitrogen and from helium- and hydrogen-like carbon in recombining plasma is evaluated. Particle simulation in the velocity space gives the time scale for relaxation of anisotropic EVDFs. (author)

  14. Ultracold Polar Molecules

    Science.gov (United States)

    2016-04-01

    AFRL-AFOSR-UK-TR-2016-0005 Ultracold Polar Molecules Jeremy Hutson UNIVERSITY OF DURHAM Final Report 04/01/2016 DISTRIBUTION A: Distribution approved...DATES COVERED (From - To) 15-Jan-2010 to 14-Jul-2015 4. TITLE AND SUBTITLE Final Report on Grant FA8655-10-1-3033 on Ultracold Polar Molecules 5a...formation of ultracold 87RbCs molecules in their rovibrational ground state by magnetoassociation followed by STIRAP, resulting in 14 papers acknowledging

  15. Hsp Polarization Verification

    Science.gov (United States)

    Bless, Robert

    1991-07-01

    This proposal defines the procedure for determining the instrumental polarization of the polarimetric IDT (IDT#1, POL) on the HSP. 1 of 2 unpolarized standard stars wil be observed using various filter-polarizer combinations. These observations will permit the instrumental polarization to be calibrated. The instrumental polarization must be determined to a high precision in order to vectoriallly remove it from HSP polarization observations to determine the actual astronomical polarization. Final run of proposal will look at one of 2 possible stars previously observed to get another look at the throughput. Revision History: Mark H. Slovak 8/30/88 Translated to V2 proposal instructions (RPSS V6.2) S. Laurent 1/20/89 Updated: Sally Laurent 2/24/89, 3/20/89, 4/13/89, 5/12/89 Modified: P. Stanley 1/15/90 - change to use CTA selected targets only; Fixes for aberration problem - SALM 7/30/90; Based on SV/HSP 1386. New submission changed targets and revised scheduling strategy. Revised: 26 Aug 92 J. Dolan, L. Walter, P. Reppert want to re-run the proposal (3985) one last time to bring down errors.

  16. Reviews in fluorescence 2007

    CERN Document Server

    Lakowicz, Joseph R; Geddes, Chris D

    2009-01-01

    This fourth volume in the Springer series summarizes the year's progress in fluorescence, with authoritative analytical reviews specialized enough for professional researchers, yet also appealing to a wider audience of scientists in related fields.

  17. Introduction to fluorescence

    CERN Document Server

    Jameson, David M

    2014-01-01

    "An essential contribution to educating scientists in the principles of fluorescence. It will also be an important addition to the libraries of practitioners applying the principles of molecular fluorescence."-Ken Jacobson, Kenan Distinguished Professor of Cell Biology and Physiology, University of North Carolina at Chapel Hill"An exquisite compendium of fluorescence and its applications in biochemistry enriched by a very exciting historical perspective. This book will become a standard text for graduate students and other scientists."-Drs. Zygmunt (Karol) Gryczynski and Ignacy Gryczynski, University of North Texas Health Science Center"… truly a masterwork, combining clarity, precision, and good humor. The reader, novice or expert, will be pleased with the text and will not stop reading. It is a formidable account of the fluorescence field, which has impacted the life sciences so considerably in the last 60 years."-Jerson L. Silva, M.D., Ph.D., Professor and Director, National Institute of Science and Tech...

  18. Polarized Light Microscopy

    Science.gov (United States)

    Frandsen, Athela F.

    2016-01-01

    Polarized light microscopy (PLM) is a technique which employs the use of polarizing filters to obtain substantial optical property information about the material which is being observed. This information can be combined with other microscopy techniques to confirm or elucidate the identity of an unknown material, determine whether a particular contaminant is present (as with asbestos analysis), or to provide important information that can be used to refine a manufacturing or chemical process. PLM was the major microscopy technique in use for identification of materials for nearly a century since its introduction in 1834 by William Fox Talbot, as other techniques such as SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared spectroscopy), XPD (X-ray Powder Diffraction), and TEM (Transmission Electron Microscopy) had not yet been developed. Today, it is still the only technique approved by the Environmental Protection Agency (EPA) for asbestos analysis, and is often the technique first applied for identification of unknown materials. PLM uses different configurations in order to determine different material properties. With each configuration additional clues can be gathered, leading to a conclusion of material identity. With no polarizing filter, the microscope can be used just as a stereo optical microscope, and view qualities such as morphology, size, and number of phases. With a single polarizing filter (single polars), additional properties can be established, such as pleochroism, individual refractive indices, and dispersion staining. With two polarizing filters (crossed polars), even more can be deduced: isotropy vs. anisotropy, extinction angle, birefringence/degree of birefringence, sign of elongation, and anomalous polarization colors, among others. With the use of PLM many of these properties can be determined in a matter of seconds, even for those who are not highly trained. McCrone, a leader in the field of polarized light microscopy, often

  19. The evolution of tensor polarization

    International Nuclear Information System (INIS)

    Huang, H.; Lee, S.Y.; Ratner, L.

    1993-01-01

    By using the equation of motion for the vector polarization, the spin transfer matrix for spin tensor polarization, the spin transfer matrix for spin tensor polarization is derived. The evolution equation for the tensor polarization is studied in the presence of an isolate spin resonance and in the presence of a spin rotor, or snake

  20. d-PET-controlled “off-on” Polarity-sensitive Probes for Reporting Local Hydrophilicity within Lysosomes

    Science.gov (United States)

    Zhu, Hao; Fan, Jiangli; Mu, Huiying; Zhu, Tao; Zhang, Zhen; Du, Jianjun; Peng, Xiaojun

    2016-10-01

    Polarity-sensitive fluorescent probes are powerful chemical tools for studying biomolecular structures and activities both in vitro and in vivo. However, the lack of “off-on” polarity-sensing probes has limited the accurate monitoring of biological processes that involve an increase in local hydrophilicity. Here, we design and synthesize a series of “off-on” polarity-sensitive fluorescent probes BP series consisting of the difluoroboron dippyomethene (BODIPY) fluorophore connected to a quaternary ammonium moiety via different carbon linkers. All these probes showed low fluorescence quantum yields in nonpolar solution but became highly fluorescent in polar media. BP-2, which contains a two-carbon linker and a trimethyl quaternary ammonium, displayed a fluorescence intensity and quantum yield that were both linearly correlated with solvent polarity. In addition, BP-2 exhibited high sensitivity and selectivity for polarity over other environmental factors and a variety of biologically relevant species. BP-2 can be synthesized readily via an unusual Mannich reaction followed by methylation. Using electrochemistry combined with theoretical calculations, we demonstrated that the “off-on” sensing behavior of BP-2 is primarily due to the polarity-dependent donor-excited photoinduced electron transfer (d-PET) effect. Live-cell imaging established that BP-2 enables the detection of local hydrophilicity within lysosomes under conditions of lysosomal dysfunction.

  1. A Brief Introduction to Single-Molecule Fluorescence Methods.

    Science.gov (United States)

    van den Wildenberg, Siet M J L; Prevo, Bram; Peterman, Erwin J G

    2018-01-01

    One of the more popular single-molecule approaches in biological science is single-molecule fluorescence microscopy, which will be the subject of the following section of this volume. Fluorescence methods provide the sensitivity required to study biology on the single-molecule level, but they also allow access to useful measurable parameters on time and length scales relevant for the biomolecular world. Before several detailed experimental approaches will be addressed, we will first give a general overview of single-molecule fluorescence microscopy. We start with discussing the phenomenon of fluorescence in general and the history of single-molecule fluorescence microscopy. Next, we will review fluorescent probes in more detail and the equipment required to visualize them on the single-molecule level. We will end with a description of parameters measurable with such approaches, ranging from protein counting and tracking, single-molecule localization super-resolution microscopy, to distance measurements with Förster Resonance Energy Transfer and orientation measurements with fluorescence polarization.

  2. Variety of Polarized Line Profiles in Interacting Supernovae

    Science.gov (United States)

    Hoffman, Jennifer L.; Huk, L. N.; Peters, C. L.

    2013-01-01

    The dense circumstellar material that creates strong emission lines in the spectra of interacting supernovae also gives rise to complex line polarization behavior. Viewed in polarized light, the emission line profiles of these supernovae encode information about the geometrical and optical characteristics of their surrounding circumstellar material (CSM) that is inaccessible by other observational techniques. To facilitate quantitative interpretation of these spectropolarimetric signatures, we have created a large grid of model polarized line profiles using a three-dimensional radiative transfer code that simulates polarization via electron and resonant/fluorescent line scattering. The simulated polarized lines take on an array of profile shapes that vary with viewing angle and CSM properties. We present the major results from the grid and investigate the dependence of polarized line profiles on CSM characteristics including temperature, optical depth, and geometry. These results will allow more straightforward interpretation of polarized line profiles in interacting supernovae than has previously been possible. This research is supported by the National Science Foundation through the AAG program and the XSEDE collaboration, and uses the resources of the Texas Advanced Computing Center.

  3. The Biosynthesis of Capuramycin-type Antibiotics

    Science.gov (United States)

    Cai, Wenlong; Goswami, Anwesha; Yang, Zhaoyong; Liu, Xiaodong; Green, Keith D.; Barnard-Britson, Sandra; Baba, Satoshi; Funabashi, Masanori; Nonaka, Koichi; Sunkara, Manjula; Morris, Andrew J.; Spork, Anatol P.; Ducho, Christian; Garneau-Tsodikova, Sylvie; Thorson, Jon S.; Van Lanen, Steven G.

    2015-01-01

    A-500359s, A-503083s, and A-102395 are capuramycin-type nucleoside antibiotics that were discovered using a screen to identify inhibitors of bacterial translocase I, an essential enzyme in peptidoglycan cell wall biosynthesis. Like the parent capuramycin, A-500359s and A-503083s consist of three structural components: a uridine-5′-carboxamide (CarU), a rare unsaturated hexuronic acid, and an aminocaprolactam, the last of which is substituted by an unusual arylamine-containing polyamide in A-102395. The biosynthetic gene clusters for A-500359s and A-503083s have been reported, and two genes encoding a putative non-heme Fe(II)-dependent α-ketoglutarate:UMP dioxygenase and an l-Thr:uridine-5′-aldehyde transaldolase were uncovered, suggesting that C–C bond formation during assembly of the high carbon (C6) sugar backbone of CarU proceeds from the precursors UMP and l-Thr to form 5′-C-glycyluridine (C7) as a biosynthetic intermediate. Here, isotopic enrichment studies with the producer of A-503083s were used to indeed establish l-Thr as the direct source of the carboxamide of CarU. With this knowledge, the A-102395 gene cluster was subsequently cloned and characterized. A genetic system in the A-102395-producing strain was developed, permitting the inactivation of several genes, including those encoding the dioxygenase (cpr19) and transaldolase (cpr25), which abolished the production of A-102395, thus confirming their role in biosynthesis. Heterologous production of recombinant Cpr19 and CapK, the transaldolase homolog involved in A-503083 biosynthesis, confirmed their expected function. Finally, a phosphotransferase (Cpr17) conferring self-resistance was functionally characterized. The results provide the opportunity to use comparative genomics along with in vivo and in vitro approaches to probe the biosynthetic mechanism of these intriguing structures. PMID:25855790

  4. Heme biosynthesis and its regulation : Toward understanding and improvement of heme biosynthesis in filamentous fungi.

    NARCIS (Netherlands)

    S. de Weert; P.J. Punt; Christien Lokman; C.A. van den Hondel; A.C. Franken; A.F. Ram

    2011-01-01

    Heme biosynthesis in fungal host strains has acquired considerable interest in relation to the production of secreted heme-containing peroxidases. Class II peroxidase enzymes have been suggested as eco-friendly replacements of polluting chemical processes in industry. These peroxidases are naturally

  5. Heme biosynthesis and its regulation: Towards understanding and improvement of heme biosynthesis in filamentous fungi

    NARCIS (Netherlands)

    Franken, A.C.W.; Lokman, B.C.; Ram, A.F.J.; Punt, P.J.; Hondel, C.A.M.J.J. van den; Weert, S. de

    2011-01-01

    Heme biosynthesis in fungal host strains has acquired considerable interest in relation to the production of secreted heme-containing peroxidases. Class II peroxidase enzymes have been suggested as eco-friendly replacements of polluting chemical processes in industry. These peroxidases are naturally

  6. Circular dichroism spectroscopy of fluorescent proteins

    NARCIS (Netherlands)

    Visser, N.V.; Hink, M.A.; Borst, J.W.; Krogt, van der G.N.M.; Visser, A.J.W.G.

    2002-01-01

    Circular dichroism (CD) spectra have been obtained from several variants of green fluorescent protein: blue fluorescent protein (BFP), enhanced cyan fluorescent protein (CFP), enhanced green fluorescent protein (GFP), enhanced yellow fluorescent protein (YFP), all from Aequorea victoria, and the red

  7. Polarized Electrons at Jefferson Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, C.K.

    1997-12-31

    The CEBAF accelerator at Jefferson laboratory can deliver CW electron beams to three experimental halls simultaneously. A large fraction of the approved scientific program at the lab requires polarized electron beams. Many of these experiments, both polarized and unpolarized, require high average beam current as well. Since all electrons delivered to the experimental halls originate from the same cathode, delivery of polarized beam to a single hall requires using the polarized source to deliver beam to all experiments in simultaneous operation. The polarized source effort at Jefferson Lab is directed at obtaining very long polarized source operational lifetimes at high average current and beam polarization; at developing the capability to deliver all electrons leaving the polarized source to the experimental halls; and at delivering polarized beam to multiple experimental halls simultaneously.initial operational experience with the polarized source will be presented.

  8. Polarized electrons at Jefferson laboratory

    International Nuclear Information System (INIS)

    The CEBAF accelerator at Jefferson laboratory can deliver CW electron beams to three experimental halls simultaneously. A large fraction of the approved scientific program at the lab requires polarized electron beams. Many of these experiments, both polarized and unpolarized, require high average beam current as well. Since all electrons delivered to the experimental halls originate from the same cathode, delivery of polarized beam to a single hall requires using the polarized source to deliver beam to all experiments in simultaneous operation. The polarized source effort at Jefferson Lab is directed at obtaining very long polarized source operational lifetimes at high average current and beam polarization; at developing the capability to deliver all electrons leaving the polarized source to the experimental halls; and at delivering polarized beam to multiple experimental halls simultaneously. Initial operational experience with the polarized source will be presented

  9. Unedoside derivatives in Nuxia and their biosynthesis

    DEFF Research Database (Denmark)

    Jensen, Søren Rosendal; Ravnkilde, Lene; Schripsema, Jan

    1998-01-01

    An investigation of two species of Nuxia showed that this genus is characterized by the presence of the eight-carbon iridoid glucoside unedoside and/or its derivatives. From N. floribunda unedoside, nuxioside (6-O-alpha-L-rhamnopyranosyl-unedoside) and 2 "-acetyl-3 "-cinnamoyl-nuxioside were...... isolated, while from N. oppositifolia 2 "-acetyl-3 "-benzoyl-nuxioside was obtained. Both plants contained verbascoside. The biosynthesis of unedoside in N. floribunda was investigated and deoxyloganic acid was found to be a precursor, similar to wh;lt was found for the eight-carbon iridoids in Thunbergia...

  10. Developing New Antibiotics with Combinatorial Biosynthesis

    Science.gov (United States)

    Pohl, Nicola L.

    2000-11-01

    Polyketide synthases (PKSs), a class of enzymes found in soil bacteria that produce antibiotics such as erythromycin, string together acetate units using basic organic reactions. The manipulation of the sequence of these reactions at the genetic level has resulted in an alteration of the corresponding chemical structure of the antibiotic produced by the bacteria. This process, called combinatorial biosynthesis, allows the generation of many presently unknown complex structures that can be tested for antibacterial activity, thereby contributing to the race against antibiotic-resistant infectious bacteria.

  11. Biosynthesis of silver nanoparticles using Saccharomyces cerevisiae.

    Science.gov (United States)

    Korbekandi, Hassan; Mohseni, Soudabeh; Mardani Jouneghani, Rasoul; Pourhossein, Meraj; Iravani, Siavash

    2016-01-01

    The objectives of this study were the biosynthesis of silver nanoparticles (NPs) by biotransformations using Saccharomyces cerevisiae and analysis of the sizes and shapes of the NPs produced. Dried and freshly cultured S. cerevisiae were used as the biocatalyst. Dried yeast synthesized few NPs, but freshly cultured yeast produced a large amount of them. Silver NPs were spherical, 2-20 nm in diameter, and the NPs with the size of 5.4 nm were the most frequent ones. NPs were seen inside the cells, within the cell membrane, attached to the cell membrane during the exocytosis, and outside of the cells.

  12. Polar low monitoring

    Science.gov (United States)

    Bobylev, Leonid; Zabolotskikh, Elizaveta; Mitnik, Leonid

    2010-05-01

    Polar lows are intense mesoscale atmospheric low pressure weather systems, developing poleward of the main baroclinic zone and associated with high surface wind speeds. Small size and short lifetime, sparse in-situ observations in the regions of their development complicate polar low study. Our knowledge of polar lows and mesocyclones has come almost entirely during the period of satellite remote sensing since, by virtue of their small horizontal scale, it was rarely possible to analyse these lows on conventional weather charts using only the data from the synoptic observing network. However, the effects of intense polar lows have been felt by coastal communities and seafarers since the earliest times. These weather systems are thought to be responsible for the loss of many small vessels over the centuries, although the nature of the storms was not understood and their arrival could not be predicted. The actuality of the polar low research is stipulated by their high destructive power: they are a threat to such businesses as oil and gas exploration, fisheries and shipping. They could worsen because of global warming: a shrinking of sea ice around the North Pole, which thawed to its record minimum in the summer of 2007, is likely to give rise to more powerful storms that form only over open water and can cause hurricane-strength winds. Therefore, study of polar lows, their timely detection, tracking and forecasting represents a challenge for today meteorology. Satellite passive microwave data, starting from Special Sensor Microwave Imager (SSM/I) onboard Defense Meteorological Satellite Program (DMSP) satellite, remain invaluable source of regularly available remotely sensed data to study polar lows. The sounding in this spectral range has several advantages in comparison with observations in visible and infrared ranges and Synthetic Aperture Radar (SAR) data: independence on day time and clouds, regularity and high temporal resolution in Polar Regions. Satellite

  13. Polarized protons at RHIC

    International Nuclear Information System (INIS)

    Tannenbaum, M.J.

    1990-12-01

    The Physics case is presented for the use of polarized protons at RHIC for one or two months each year. This would provide a facility with polarizations of approx-gt 50% high luminosity ∼2.0 x 10 32 cm -2 s -1 , the possibility of both longitudinal and transverse polarization at the interaction regions, and frequent polarization reversal for control of systematic errors. The annual integrated luminosity for such running (∼10 6 sec per year) would be ∫ Ldt = 2 x 10 38 cm -2 -- roughly 20 times the total luminosity integrated in ∼ 10 years of operation of the CERN Collider (∼10 inverse picobarns, 10 37 cm -2 ). This facility would be unique in the ability to perform parity-violating measurements and polarization test of QCD. Also, the existence of p-p collisions in a new energy range would permit the study of ''classical'' reactions like the total cross section and elastic scattering, etc., and serve as a complement to measurements from p-bar p colliders. 11 refs

  14. The Bochum Polarized Target

    International Nuclear Information System (INIS)

    Reicherz, G.; Goertz, S.; Harmsen, J.; Heckmann, J.; Meier, A.; Meyer, W.; Radtke, E.

    2001-01-01

    The Bochum 'Polarized Target' group develops the target material 6 LiD for the COMPASS experiment at CERN. Several different materials like alcohols, alcanes and ammonia are under investigation. Solid State Targets are polarized in magnetic fields higher than B=2.5T and at temperatures below T=1K. For the Dynamic Nuclear Polarization process, paramagnetic centers are induced chemically or by irradiation with ionizing beams. The radical density is a critical factor for optimization of polarization and relaxation times at adequate magnetic fields and temperatures. In a high sensitive EPR--apparatus, an evaporator and a dilution cryostat with a continuous wave NMR--system, the materials are investigated and optimized. To improve the polarization measurement, the Liverpool NMR-box is modified by exchanging the fixed capacitor for a varicap diode which not only makes the tuning very easy but also provides a continuously tuned circuit. The dependence of the signal area upon the circuit current is measured and it is shown that it follows a linear function

  15. In-line Fiber Polarizer

    OpenAIRE

    Perumalsamy, Priya

    1998-01-01

    Polarizers and polarization devices are important components in fiber optic communication and sensor systems. There is a growing need for efficient low loss components that are compatible with optical fibers. An all fiber in-line polarizer is a more desirable alternative that could be placed at appropriate intervals along communication links. An in-line fiber polarizer was fabricated and tested. The in-line fiber polarizer operates by coupling optical energy propagatin...

  16. Green biosynthesis of silver nanoparticles using Curcuma longa tuber powder

    Directory of Open Access Journals (Sweden)

    Shameli K

    2012-10-01

    Full Text Available Kamyar Shameli,1,2 Mansor Bin Ahmad,1 Ali Zamanian,2 Parvanh Sangpour,2 Parvaneh Shabanzadeh,3 Yadollah Abdollahi,4 Mohsen Zargar51Department of Chemistry, Universiti Putra Malaysia, Serdang, Selangor, Malaysia; 2Materials and Energy Research Center, Karaj, Iran; 3Department of Mathematics, 4Advanced Materials and Nanotechnology Laboratory, Universiti Putra Malaysia, Serdang, Selangor, Malaysia; 5Department of Biology, Islamic Azad University, Qom, IranAbstract: Green synthesis of noble metal nanoparticles is a vastly developing area of research. Metallic nanoparticles have received great attention from chemists, physicists, biologists, and engineers who wish to use them for the development of a new-generation of nanodevices. In this study, silver nanoparticles were biosynthesized from aqueous silver nitrate through a simple and eco-friendly route using Curcuma longa tuber-powder extracts, which acted as a reductant and stabilizer simultaneously. Characterizations of nanoparticles were done using different methods, which included ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray fluorescence spectrometry, and Fourier-transform infrared spectroscopy. The ultraviolet-visible spectrum of the aqueous medium containing silver nanoparticles showed an absorption peak at around 415 nm. Transmission electron microscopy showed that mean diameter and standard deviation for the formation of silver nanoparticles was 6.30 ± 2.64 nm. Powder X-ray diffraction showed that the particles are crystalline in nature, with a face-centered cubic structure. The most needed outcome of this work will be the development of value-added products from C. longa for biomedical and nanotechnology-based industries.Keywords: silver nanoparticles, Curcuma longa, biosynthesis, green synthesis, transmission electron microscopy

  17. A polarized view on DNA under tension

    Science.gov (United States)

    van Mameren, Joost; Vermeulen, Karen; Wuite, Gijs J. L.; Peterman, Erwin J. G.

    2018-03-01

    In the past decades, sensitive fluorescence microscopy techniques have contributed significantly to our understanding of the dynamics of DNA. The specific labeling of DNA using intercalating dyes has allowed for quantitative measurement of the thermal fluctuations the polymers undergo. On the other hand, recent advances in single-molecule manipulation techniques have unraveled the mechanical and elastic properties of this intricate polymer. Here, we have combined these two approaches to study the conformational dynamics of DNA under a wide range of tensions. Using polarized fluorescence microscopy in conjunction with optical-tweezers-based manipulation of YOYO-intercalated DNA, we controllably align the YOYO dyes using DNA tension, enabling us to disentangle the rapid dynamics of the dyes from that of the DNA itself. With unprecedented control of the DNA alignment, we resolve an inconsistency in reports about the tilted orientation of intercalated dyes. We find that intercalated dyes are on average oriented perpendicular to the long axis of the DNA, yet undergo fast dynamics on the time scale of absorption and fluorescence emission. In the overstretching transition of double-stranded DNA, we do not observe changes in orientation or orientational dynamics of the dyes. Only beyond the overstretching transition, a considerable depolarization is observed, presumably caused by an average tilting of the DNA base pairs. Our combined approach thus contributes to the elucidation of unique features of the molecular dynamics of DNA.

  18. Political Competition and Polarization

    DEFF Research Database (Denmark)

    Schultz, Christian

    This paper considers political competition and the consequences of political polarization when parties are better informed about how the economy functions than voters are. Specifically, parties know the cost producing a public good, voters do not. An incumbent's choice of policy acts like a signa...... for costs before an upcoming election. It is shown that the more polarized the political parties the more distorted the incumbent's policy choice.......This paper considers political competition and the consequences of political polarization when parties are better informed about how the economy functions than voters are. Specifically, parties know the cost producing a public good, voters do not. An incumbent's choice of policy acts like a signal...

  19. Physics of polarized targets

    CERN Document Server

    Niinikoski, Tapio

    2014-01-01

    For developing, building and operating solid polarized targets we need to understand several fields of physics that have seen sub stantial advances during the last 50 years. W e shall briefly review a selection of those that are important today. These are: 1) quantum statistical methods to describe saturation and relaxation in magnetic resonance; 2) equal spin temperature model for dy namic nuclear polarization; 3 ) weak saturation during NMR polarization measurement; 4 ) refrigeration using the quantum fluid properties of helium isotopes. These, combined with superconducting magnet technologies, permit today to reach nearly complete pola rization of almost any nuclear spins. Targets can be operated in frozen spin mode in rather low and inhomogeneous field of any orientation, and in DNP mode in beams of high intensity. Beyond such experiments of nuclear and particle physics, applications a re also emerging in macromolecular chemistry and in magnetic resonance imaging. This talk is a tribute to Michel Borghini...

  20. No More Polarization, Please!

    DEFF Research Database (Denmark)

    Hansen, Mia Reinholt

    The organizational science literature on motivation has for long been polarized into two main positions; the organizational economic position focusing on extrinsic motivation and the organizational behavior position emphasizing intrinsic motivation. With the rise of the knowledge economy...... and the increasing levels of complexities it entails, such polarization is not fruitful in the attempt to explain motivation of organizational members. This paper claims that a more nuanced perspective on motivation, acknowledging the co-existence of intrinsic and extrinsic motivation, the possible interaction...... between the two as well as different types of motivations filling in the gap between the two polar types, is urgently needed in the organizational science literature. By drawing on the research on intrinsic and extrinsic motivation conducted in social psychology and combining this with contributions from...

  1. Polarized source upgrading

    International Nuclear Information System (INIS)

    Clegg, T.B.; Rummel, R.L.; Carter, E.P.; Westerfeldt, C.R.; Lovette, A.W.; Edwards, S.E.

    1985-01-01

    The decision was made this past year to move the Lamb-shift polarized ion source which was first installed in the laboratory in 1970. The motivation was the need to improve the flexibility of spin-axis orientation by installing the ion source with a new Wien-filter spin precessor which is capable of rotating physically about the beam axis. The move of the polarized source was accomplished in approximately two months, with the accelerator being turned off for experiments during approximately four weeks of this time. The occasion of the move provided the opportunity to rewire completely the entire polarized ion source frame and to rebuild approximately half of the electronic chassis on the source. The result is an ion source which is now logically wired and carefully documented. Beams obtained from the source are much more stable than those previously available

  2. A lunar polar expedition

    Science.gov (United States)

    Dowling, Richard; Staehle, Robert L.; Svitek, Tomas

    1992-09-01

    Advanced exploration and development in harsh environments require mastery of basic human survival skill. Expeditions into the lethal climates of Earth's polar regions offer useful lessons for tommorrow's lunar pioneers. In Arctic and Antarctic exploration, 'wintering over' was a crucial milestone. The ability to establish a supply base and survive months of polar cold and darkness made extensive travel and exploration possible. Because of the possibility of near-constant solar illumination, the lunar polar regions, unlike Earth's may offer the most hospitable site for habitation. The World Space Foundation is examining a scenario for establishing a five-person expeditionary team on the lunar north pole for one year. This paper is a status report on a point design addressing site selection, transportation, power, and life support requirements.

  3. Green fluorescent protein.

    Science.gov (United States)

    Chalfie, M

    1995-10-01

    Several bioluminescent coelenterates use a secondary fluorescent protein, the green fluorescent protein (GFP), in an energy transfer reaction to produce green light. The most studied of these proteins have been the GFPs from the jellyfish Aequorea victoria and the sea pansy Renilla reniformis. Although the proteins from these organisms are not identical, they are thought to have the same chromophore, which is derived from the primary amino acid sequence of GFP. The differences are thought to be due to changes in the protein environment of the chromophore. Recent interest in these molecules has arisen from the cloning of the Aequorea gfp cDNA and the demonstration that its expression in the absence of other Aequorea proteins results in a fluorescent product. This demonstration indicated that GFP could be used as a marker of gene expression and protein localization in living and fixed tissues. Bacterial, plant and animal (including mammalian) cells all express GFP. The heterologous expression of the gfp cDNA has also meant that it could be mutated to produce proteins with different fluorescent properties. Variants with more intense fluorescence or alterations in the excitation and emission spectra have been produced.

  4. POLARIZED NEUTRONS IN RHIC

    Energy Technology Data Exchange (ETDEWEB)

    COURANT,E.D.

    1998-04-27

    There does not appear to be any obvious way to accelerate neutrons, polarized or otherwise, to high energies by themselves. To investigate the behavior of polarized neutrons the authors therefore have to obtain them by accelerating them as components of heavier nuclei, and then sorting out the contribution of the neutrons in the analysis of the reactions produced by the heavy ion beams. The best neutron carriers for this purpose are probably {sup 3}He nuclei and deuterons. A polarized deuteron is primarily a combination of a proton and a neutron with their spins pointing in the same direction; in the {sup 3}He nucleus the spins of the two protons are opposite and the net spin (and magnetic moment) is almost the same as that of a free neutron. Polarized ions other than protons may be accelerated, stored and collided in a ring such as RHIC provided the techniques proposed for polarized proton operation can be adapted (or replaced by other strategies) for these ions. To accelerate polarized particles in a ring, one must make provisions for overcoming the depolarizing resonances that occur at certain energies. These resonances arise when the spin tune (ratio of spin precession frequency to orbit frequency) resonates with a component present in the horizontal field. The horizontal field oscillates with the vertical motion of the particles (due to vertical focusing); its frequency spectrum is dominated by the vertical oscillation frequency and its modulation by the periodic structure of the accelerator ring. In addition, the magnet imperfections that distort the closed orbit vertically contain all integral Fourier harmonics of the orbit frequency.

  5. Isoprenoid Biosynthesis Inhibitors Targeting Bacterial Cell Growth.

    Science.gov (United States)

    Desai, Janish; Wang, Yang; Wang, Ke; Malwal, Satish R; Oldfield, Eric

    2016-10-06

    We synthesized potential inhibitors of farnesyl diphosphate synthase (FPPS), undecaprenyl diphosphate synthase (UPPS), or undecaprenyl diphosphate phosphatase (UPPP), and tested them in bacterial cell growth and enzyme inhibition assays. The most active compounds were found to be bisphosphonates with electron-withdrawing aryl-alkyl side chains which inhibited the growth of Gram-negative bacteria (Acinetobacter baumannii, Klebsiella pneumoniae, Escherichia coli, and Pseudomonas aeruginosa) at ∼1-4 μg mL -1 levels. They were found to be potent inhibitors of FPPS; cell growth was partially "rescued" by the addition of farnesol or overexpression of FPPS, and there was synergistic activity with known isoprenoid biosynthesis pathway inhibitors. Lipophilic hydroxyalkyl phosphonic acids inhibited UPPS and UPPP at micromolar levels; they were active (∼2-6 μg mL -1 ) against Gram-positive but not Gram-negative organisms, and again exhibited synergistic activity with cell wall biosynthesis inhibitors, but only indifferent effects with other inhibitors. The results are of interest because they describe novel inhibitors of FPPS, UPPS, and UPPP with cell growth inhibitory activities as low as ∼1-2 μg mL -1 . © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. BIOSYNTHESIS AND PROPERTIES OF ANTIBIOTIC BATUMIN

    Directory of Open Access Journals (Sweden)

    V. V. Klochko

    2014-12-01

    Full Text Available Biosynthesis of antistaphylococcal antibiotic batumin under periodic conditions of Pseudomonas batumici growth has been studied. Antibiotic synthesis in fermenter occurred across the culture growth and achieved its maximal value after 50–55 hours. The active oxygen utilization by the producing strain was observed during 20–55 hours of fermentation with maximum after 40–45 hours. Antibiotic yield was 175–180 mg/l and depended on intensity of aeration. contrast to «freshly isolated» antibiotic after fermentation the long-term kept batumin has shown two identical by molecular mass peaks according to the chromato-mass spectrometric analysis. Taking into account of batumin molecule structure the conclusion has been made that the most probable isomerization type is keto-enolic tautomerism. At the same time batumin is diastereoisomer of kalimantacin A which has the same chemical structure. The optic rotation angle is [α]d25 = +56.3° for kalimantacin and [α]d25 = –13.5° for batumin. The simultaneous P. batumici growth and antibiotic biosynthesis and the ability of this molecule to optical isomerisation and keto-enolic forms formation allow us to suppose that batumin plays a certain role in metabolism of the producing strain.

  7. Essences in Metabolic Engineering of Lignan Biosynthesis

    Directory of Open Access Journals (Sweden)

    Honoo Satake

    2015-05-01

    Full Text Available Lignans are structurally and functionally diverse phytochemicals biosynthesized in diverse plant species and have received wide attentions as leading compounds of novel drugs for tumor treatment and healthy diets to reduce of the risks of lifestyle-related non-communicable diseases. However, the lineage-specific distribution and the low-amount of production in natural plants, some of which are endangered species, hinder the efficient and stable production of beneficial lignans. Accordingly, the development of new procedures for lignan production is of keen interest. Recent marked advances in the molecular and functional characterization of lignan biosynthetic enzymes and endogenous and exogenous factors for lignan biosynthesis have suggested new methods for the metabolic engineering of lignan biosynthesis cascades leading to the efficient, sustainable, and stable lignan production in plants, including plant cell/organ cultures. Optimization of light conditions, utilization of a wide range of elicitor treatments, and construction of transiently gene-transfected or transgenic lignan-biosynthesizing plants are mainly being attempted. This review will present the basic and latest knowledge regarding metabolic engineering of lignans based on their biosynthetic pathways and biological activities, and the perspectives in lignan production via metabolic engineering.

  8. Fatty acid biosynthesis in pea root plastids

    International Nuclear Information System (INIS)

    Stahl, R.J.; Sparace, S.A.

    1989-01-01

    Fatty acid biosynthesis from [1- 14 C]acetate was optimized in plastids isolated from primary root tips of 7-day-old germinating pea seeds. Fatty acid synthesis was maximum at approximately 80 nmoles/hr/mg protein in the presence of 200 μM acetate, 0.5 mM each of NADH, NADPH and CoA, 6 mM each of ATP and MgCl 2 , 1 mM each of the MnCl 2 and glycerol-3-phosphate, 15 mM KHCO 3 , and 0.1M Bis-tris-propane, pH 8.0 incubated at 35C. At the standard incubation temperature of 25C, fatty acid synthesis was linear from up to 6 hours with 80 to 100 μg/mL plastid protein. ATP and CoA were absolute requirements, whereas KHCO 3 , divalent cations and reduced nucleotides all improved activity by 80 to 85%. Mg 2+ and NADH were the preferred cation and nucleotide, respectively. Dithiothreitol and detergents were generally inhibitory. The radioactive products of fatty acid biosynthesis were approximately 33% 16:0, 10% 18:0 and 56% 18:1 and generally did not vary with increasing concentrations of each cofactor

  9. Benzylisoquinoline alkaloid biosynthesis in opium poppy.

    Science.gov (United States)

    Beaudoin, Guillaume A W; Facchini, Peter J

    2014-07-01

    Opium poppy (Papaver somniferum) is one of the world's oldest medicinal plants and remains the only commercial source for the narcotic analgesics morphine, codeine and semi-synthetic derivatives such as oxycodone and naltrexone. The plant also produces several other benzylisoquinoline alkaloids with potent pharmacological properties including the vasodilator papaverine, the cough suppressant and potential anticancer drug noscapine and the antimicrobial agent sanguinarine. Opium poppy has served as a model system to investigate the biosynthesis of benzylisoquinoline alkaloids in plants. The application of biochemical and functional genomics has resulted in a recent surge in the discovery of biosynthetic genes involved in the formation of major benzylisoquinoline alkaloids in opium poppy. The availability of extensive biochemical genetic tools and information pertaining to benzylisoquinoline alkaloid metabolism is facilitating the study of a wide range of phenomena including the structural biology of novel catalysts, the genomic organization of biosynthetic genes, the cellular and sub-cellular localization of biosynthetic enzymes and a variety of biotechnological applications. In this review, we highlight recent developments and summarize the frontiers of knowledge regarding the biochemistry, cellular biology and biotechnology of benzylisoquinoline alkaloid biosynthesis in opium poppy.

  10. Molecular Regulation of Antibiotic Biosynthesis in Streptomyces

    Science.gov (United States)

    Liu, Gang; Chandra, Govind; Niu, Guoqing

    2013-01-01

    SUMMARY Streptomycetes are the most abundant source of antibiotics. Typically, each species produces several antibiotics, with the profile being species specific. Streptomyces coelicolor, the model species, produces at least five different antibiotics. We review the regulation of antibiotic biosynthesis in S. coelicolor and other, nonmodel streptomycetes in the light of recent studies. The biosynthesis of each antibiotic is specified by a large gene cluster, usually including regulatory genes (cluster-situated regulators [CSRs]). These are the main point of connection with a plethora of generally conserved regulatory systems that monitor the organism's physiology, developmental state, population density, and environment to determine the onset and level of production of each antibiotic. Some CSRs may also be sensitive to the levels of different kinds of ligands, including products of the pathway itself, products of other antibiotic pathways in the same organism, and specialized regulatory small molecules such as gamma-butyrolactones. These interactions can result in self-reinforcing feed-forward circuitry and complex cross talk between pathways. The physiological signals and regulatory mechanisms may be of practical importance for the activation of the many cryptic secondary metabolic gene cluster pathways revealed by recent sequencing of numerous Streptomyces genomes. PMID:23471619

  11. Biosynthesis of nanoparticles using microbes- a review.

    Science.gov (United States)

    Hulkoti, Nasreen I; Taranath, T C

    2014-09-01

    The biosynthesis of nanoparticles by microorganism is a green and eco-friendly technology. This review focuses on the use of consortium of diverse microorganisms belonging to both prokaryotes and eukaryotes for the synthesis of metallic nanoparticles viz. silver, gold, platinum, zirconium, palladium, iron, cadmium and metal oxides such as titanium oxide, zinc oxide, etc. These microorganisms include bacteria, actinomycetes, fungi and algae. The synthesis of nanoparticles may be intracellular or extracellular. The several workers have reported that NADH dependent nitrate reductase enzyme plays a vital role in the conversion of metallic ions to nanoparticles. The FTIR study reveals that diverse biomolecules viz. carboxyl group, primary and secondary amines, amide I, II, and III bands etc serve as a tool for bioreduction and capping agents there by offering stability to particles by preventing agglomeration and growth. The size and shape of the nanoparticles vary with the organism employed and conditions employed during the synthesis which included pH, temperature and substrate concentration. The microorganisms provide diverse environment for biosynthesis of nanoparticles. These particles are safe and eco-friendly with a lot of applications in medicine, agriculture, cosmetic industry, drug delivery and biochemical sensors. The challenges for redressal include optimal production and minimal time to obtain desired size and shape, to enhance the stability of nanoparticles and optimization of specific microorganisms for specific application. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Dark Polar Dunes

    Science.gov (United States)

    2005-01-01

    20 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired during northern summer in December 2004, shows dark, windblown sand dunes in the north polar region of Mars. A vast sea of sand dunes nearly surrounds the north polar cap. These landforms are located near 80.3oN, 144.1oW. Light-toned features in the image are exposures of the substrate that underlies the dune field. The image covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the lower left.

  13. Imaging with Polarized Neutrons

    Directory of Open Access Journals (Sweden)

    Nikolay Kardjilov

    2018-01-01

    Full Text Available Owing to their zero charge, neutrons are able to pass through thick layers of matter (typically several centimeters while being sensitive to magnetic fields due to their intrinsic magnetic moment. Therefore, in addition to the conventional attenuation contrast image, the magnetic field inside and around a sample can be visualized by detecting changes of polarization in a transmitted beam. The method is based on the spatially resolved measurement of the cumulative precession angles of a collimated, polarized, monochromatic neutron beam that traverses a magnetic field or sample.

  14. The polar mesosphere

    International Nuclear Information System (INIS)

    Morris, Ray; Murphy, Damian

    2008-01-01

    The mesosphere region, which lies at the edge of space, contains the coldest layer of the Earth's atmosphere, with summer temperatures as low as minus 130 °C. In this extreme environment ice aerosol layers have appeared since the dawn of industrialization—whose existence may arguably be linked to human influence—on yet another layer of the Earth's fragile atmosphere. Ground-based and space-based experiments conducted in the Arctic and Antarctic during the International Polar Year (IPY) aim to address limitations in our knowledge and to advance our understanding of thermal and dynamical processes at play in the polar mesosphere

  15. Internal polarized targets

    Energy Technology Data Exchange (ETDEWEB)

    Kinney, E.R.; Coulter, K.; Gilman, R.; Holt, R.J.; Kowalczyk, R.S.; Napolitano, J.; Potterveld, D.H.; Young, L. (Argonne National Lab., IL (USA)); Mishnev, S.I.; Nikolenko, D.M.; Popov, S.G.; Rachek, I.A.; Temnykh, A.B.; Toporkov, D.K.; Tsentalovich, E.P.; Wojtsekhowski, B.B. (AN SSSR, Novosibirsk (USSR). Inst. Yadernoj Fiziki)

    1989-01-01

    Internal polarized targets offer a number of advantages over external targets. After a brief review of the basic motivation and principles behind internal polarized targets, the technical aspects of the atomic storage cell will be discussed in particular. Sources of depolarization and the means by which their effects can be ameliorated will be described, especially depolarization by the intense magnetic fields arising from the circulating particle beam. The experience of the Argonne Novosibirsk collaboration with the use of a storage cell in a 2 GeV electron storage ring will be the focus of this technical discussion. 17 refs., 11 figs.

  16. AGS polarized H- source

    International Nuclear Information System (INIS)

    Kponou, A.; Alessi, J.G.; Sluyters, T.

    1985-01-01

    The AGS polarized H - source is now operational. During a month-long experimental physics run in July 1984, pulses equivalent to 15 μA x 300 μs (approx. 3 x 10 10 protons) were injected into the RFQ preaccelerator. Beam polarization, measured at 200 MeV, was approx. 75%. After the run, a program to increase the H - yield of the source was begun and significant progress has been made. The H - current is now frequently 20 to 30 μA. A description of the source and some details of our operating experience are given. We also briefly describe the improvement program

  17. Rare cause of post-squalene disorder of cholesterol biosynthesis ...

    African Journals Online (AJOL)

    Errors of cholesterol biosynthesis represent a heterogeneous group of metabolic disorders. The aim of the authors of this article is to present a case of a patient with typical symptoms of a rare post-squalene disorder of cholesterol biosynthesis, its diagnostics and progress in neonatal period. The differential diagnosis of a ...

  18. Rapid biosynthesis of cadmium sulfide (CdS) nanoparticles using ...

    African Journals Online (AJOL)

    Rapid biosynthesis of cadmium sulfide (CdS) nanoparticles using culture supernatants of Escherichia coli ATCC 8739, Bacillus subtilis ATCC 6633 and Lactobacillus ... The process of extracellular and fast biosynthesis may help in the development of an easy and eco-friendly route for the synthesis of CdS nanoparticles.

  19. Ant trail pheromone biosynthesis is triggered by a neuropeptide hormone.

    Directory of Open Access Journals (Sweden)

    Man-Yeon Choi

    Full Text Available Our understanding of insect chemical communication including pheromone identification, synthesis, and their role in behavior has advanced tremendously over the last half-century. However, endocrine regulation of pheromone biosynthesis has progressed slowly due to the complexity of direct and/or indirect hormonal activation of the biosynthetic cascades resulting in insect pheromones. Over 20 years ago, a neurohormone, pheromone biosynthesis activating neuropeptide (PBAN was identified that stimulated sex pheromone biosynthesis in a lepidopteran moth. Since then, the physiological role, target site, and signal transduction of PBAN has become well understood for sex pheromone biosynthesis in moths. Despite that PBAN-like peptides (∼200 have been identified from various insect Orders, their role in pheromone regulation had not expanded to the other insect groups except for Lepidoptera. Here, we report that trail pheromone biosynthesis in the Dufour's gland (DG of the fire ant, Solenopsis invicta, is regulated by PBAN. RNAi knock down of PBAN gene (in subesophageal ganglia or PBAN receptor gene (in DG expression inhibited trail pheromone biosynthesis. Reduced trail pheromone was documented analytically and through a behavioral bioassay. Extension of PBAN's role in pheromone biosynthesis to a new target insect, mode of action, and behavioral function will renew research efforts on the involvement of PBAN in pheromone biosynthesis in Insecta.

  20. Electric field effects on fluorescence of the green fluorescent protein

    Science.gov (United States)

    Nakabayashi, Takakazu; Kinjo, Masataka; Ohta, Nobuhiro

    2008-05-01

    External electric field effects on state energy and photoexcitation dynamics have been examined for a mutant of UV-excited green fluorescent protein (GFPuv5) in a PVA film. The electrofluorescence spectrum of GFPuv5 is reproduced by a linear combination between the fluorescence spectrum and its second derivative spectrum, indicating the field-induced fluorescence quenching and the difference in electric dipole moment between the fluorescent state and the ground state. The direct measurements of the field-induced change in fluorescence decay show that the field-induced quenching results from the field-induced increase in the rate of the non-radiative process from the fluorescent state.

  1. The physics of polarization

    Science.gov (United States)

    Landi Degl'Innocenti, Egidio

    This course is intended to give a description of the basic physical concepts which underlie the study and the interpretation of polarization phenomena. Apart from a brief historical introduction (Sect. 1), the course is organized in three parts. A first part (Sects. 2 - 6) covers the most relevant facts about the polarization phenomena that are typically encountered in laboratory applications and in everyday life. In Sect. 2, the modern description of polarization in terms of the Stokes parameters is recalled, whereas Sect. 3 is devoted to introduce the basic tools of laboratory polarimetry, such as the Jones calculus and the Mueller matrices. The polarization phenomena which are met in the reflection and refraction of a beam of radiation at the separation surface between two dielectrics, or between a dielectric and a metal, are recalled in Sect. 4. Finally, Sect. 5 gives an introduction to the phenomena of dichroism and of anomalous dispersion and Sect. 6 summarizes the polarization phenomena that are commonly encountered in everyday life. The second part of this course (Sects. 7-14) deals with the description, within the formalism of classical physics, of the spectro-polarimetric properties of the radiation emitted by accelerated charges. Such properties are derived by taking as starting point the Liénard and Wiechert equations that are recalled and discussed in Sect. 7 both in the general case and in the non-relativistic approximation. The results are developed to find the percentage polarization, the radiation diagram, the cross-section and the spectral characteristics of the radiation emitted in different phenomena particularly relevant from the astrophysical point of view. The emission of a linear antenna is derived in Sect. 8. The other Sections are devoted to Thomson scattering (Sect. 9), Rayleigh scattering (Sect. 10), Mie scattering (Sect. 11), bremsstrahlung radiation (Sect. 12), cyclotron radiation (Sect. 13), and synchrotron radiation (Sect. 14

  2. Polarized Proton Collisions at RHIC

    CERN Document Server

    Bai, Mei; Alekseev, Igor G; Alessi, James; Beebe-Wang, Joanne; Blaskiewicz, Michael; Bravar, Alessandro; Brennan, Joseph M; Bruno, Donald; Bunce, Gerry; Butler, John J; Cameron, Peter; Connolly, Roger; De Long, Joseph; Drees, Angelika; Fischer, Wolfram; Ganetis, George; Gardner, Chris J; Glenn, Joseph; Hayes, Thomas; Hseuh Hsiao Chaun; Huang, Haixin; Ingrassia, Peter; Iriso, Ubaldo; Laster, Jonathan S; Lee, Roger C; Luccio, Alfredo U; Luo, Yun; MacKay, William W; Makdisi, Yousef; Marr, Gregory J; Marusic, Al; McIntyre, Gary; Michnoff, Robert; Montag, Christoph; Morris, John; Nicoletti, Tony; Oddo, Peter; Oerter, Brian; Osamu, Jinnouchi; Pilat, Fulvia Caterina; Ptitsyn, Vadim; Roser, Thomas; Satogata, Todd; Smith, Kevin T; Svirida, Dima; Tepikian, Steven; Tomas, Rogelio; Trbojevic, Dejan; Tsoupas, Nicholaos; Tuozzolo, Joseph; Vetter, Kurt; Wilinski, Michelle; Zaltsman, Alex; Zelenski, Anatoli; Zeno, Keith; Zhang, S Y

    2005-01-01

    The Relativistic Heavy Ion Collider~(RHIC) provides not only collisions of ions but also collisions of polarized protons. In a circular accelerator, the polarization of polarized proton beam can be partially or fully lost when a spin depolarizing resonance is encountered. To preserve the beam polarization during acceleration, two full Siberian snakes were employed in RHIC to avoid depolarizing resonances. In 2003, polarized proton beams were accelerated to 100~GeV and collided in RHIC. Beams were brought into collisions with longitudinal polarization at the experiments STAR and PHENIX by using spin rotators. RHIC polarized proton run experience demonstrates that optimizing polarization transmission efficiency and improving luminosity performance are significant challenges. Currently, the luminosity lifetime in RHIC is limited by the beam-beam effect. The current state of RHIC polarized proton program, including its dedicated physics run in 2005 and efforts to optimize luminosity production in beam-beam limite...

  3. Concentrators using fluorescent substances

    Energy Technology Data Exchange (ETDEWEB)

    Hayashibara, M.; Tsukamoto, M. (Hitachi Seisakusho K.K., Tokyo (Japan))

    1990-01-01

    In luminescent concentrators - plates of polymethylmethacrylate (PMMA) or other transparent material with a fluorescent compound dispersed within them - incident light is trapped and concentrated by internal reflection, and shifted to a longer wavelength, as it interacts with fluorescent particles. Experience with the use of luminescent concentrators for electricity generation in conjunction with solar cells, in solar heaters, in amplifiers for light intensity, in long-wave converters and in display panels is discussed. Solar energy conversion efficiencies of 4-5% have been obtained in generating systems combining concentrators containing Fluorol 555 or Rhodamin 6G with GaAs solar cells. (author).

  4. Fluorescence uranium determination

    International Nuclear Information System (INIS)

    Fernandez Cellini, R.; Crus Castillo, F. de la; Barrera Pinero, R.

    1960-01-01

    An equipment for analysis of uranium by fluorescence was developed in order to determine it at such a low concentration that it can not be determined by the most sensible analytical methods. this new fluorimeter was adapted to measure the fluorescence emitted by the phosphorus sodium fluoride-sodium carbonate-potasium carbonate-uranyl, being excited by ultraviolet light of 3,650 A the intensity of the light emitted was measure with a photomultiplicator RCA 5819 and the adequate electronic equipment. (Author) 19 refs

  5. Lobbying and political polarization

    OpenAIRE

    Ursprung, Heinrich W.

    2002-01-01

    Standard spatial models of political competition give rise to equilibria in which the competing political parties or candidates converge to a common position. In this paper I show how political polarization can be generated in models that focus on the nexus between pre-election interest group lobbying and electoral competition.

  6. Polarization of Bremsstrahlung

    International Nuclear Information System (INIS)

    Miller, J.

    1957-01-01

    The numerical results for the polarization of Bremsstrahlung are presented. The multiple scattering of electrons in the target is taken into account. The angular-and photon energy dependences are seen on the curves for an incident 25 MeV electron energy. (Author) [fr

  7. DESY: HERA polarization

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    The new HERA electron-proton collider at DESY in Hamburg achieved the first luminosity for electron-proton collisions on 19 October last year. Only one month later, on 20 November, HERA passed another important milestone with the observation of transverse electron polarization

  8. Titan Polar Landscape Evolution

    Science.gov (United States)

    Moore, Jeffrey M.

    2016-01-01

    With the ongoing Cassini-era observations and studies of Titan it is clear that the intensity and distribution of surface processes (particularly fluvial erosion by methane and Aeolian transport) has changed through time. Currently however, alternate hypotheses substantially differ among specific scenarios with respect to the effects of atmospheric evolution, seasonal changes, and endogenic processes. We have studied the evolution of Titan's polar region through a combination of analysis of imaging, elevation data, and geomorphic mapping, spatially explicit simulations of landform evolution, and quantitative comparison of the simulated landscapes with corresponding Titan morphology. We have quantitatively evaluated alternate scenarios for the landform evolution of Titan's polar terrain. The investigations have been guided by recent geomorphic mapping and topographic characterization of the polar regions that are used to frame hypotheses of process interactions, which have been evaluated using simulation modeling. Topographic information about Titan's polar region is be based on SAR-Topography and altimetry archived on PDS, SAR-based stereo radar-grammetry, radar-sounding lake depth measurements, and superposition relationships between geomorphologic map units, which we will use to create a generalized topographic map.

  9. Graphics of polar figure

    International Nuclear Information System (INIS)

    Macias B, L.R.

    1991-11-01

    The objective of this work, is that starting from a data file coming from a spectra that has been softened, and of the one that have been generated its coordinates to project it in stereographic form, to create the corresponding polar figure making use of the Cyber computer of the ININ by means of the GRAPHOS package. This work only requires a Beta, Fi and Intensity (I) enter data file. It starts of the existence of a softened spectra of which have been generated already with these data, making use of some language that in this case was FORTRAN for the Cyber computer, a program is generated supported in the Graphos package that allows starting of a reading of the Beta, Fi, I file, to generate the points in a stereographic projection and that it culminates with the graph of the corresponding polar figure. The program will request the pertinent information that is wanted to capture in the polar figure just as: date, name of the enter file, indexes of the polar figure, number of levels, radio of the stereographic projection (cms.), crystalline system to which belongs the sample, name the neuter graph file by create and to add the own general data. (Author)

  10. Identification of a flavin-containing S-oxygenating monooxygenase involved in alliin biosynthesis in garlic.

    Science.gov (United States)

    Yoshimoto, Naoko; Onuma, Misato; Mizuno, Shinya; Sugino, Yuka; Nakabayashi, Ryo; Imai, Shinsuke; Tsuneyoshi, Tadamitsu; Sumi, Shin-ichiro; Saito, Kazuki

    2015-09-01

    S-Alk(en)yl-l-cysteine sulfoxides are cysteine-derived secondary metabolites highly accumulated in the genus Allium. Despite pharmaceutical importance, the enzymes that contribute to the biosynthesis of S-alk-(en)yl-l-cysteine sulfoxides in Allium plants remain largely unknown. Here, we report the identification of a flavin-containing monooxygenase, AsFMO1, in garlic (Allium sativum), which is responsible for the S-oxygenation reaction in the biosynthesis of S-allyl-l-cysteine sulfoxide (alliin). Recombinant AsFMO1 protein catalyzed the stereoselective S-oxygenation of S-allyl-l-cysteine to nearly exclusively yield (RC SS )-S-allylcysteine sulfoxide, which has identical stereochemistry to the major natural form of alliin in garlic. The S-oxygenation reaction catalyzed by AsFMO1 was dependent on the presence of nicotinamide adenine dinucleotide phosphate (NADPH) and flavin adenine dinucleotide (FAD), consistent with other known flavin-containing monooxygenases. AsFMO1 preferred S-allyl-l-cysteine to γ-glutamyl-S-allyl-l-cysteine as the S-oxygenation substrate, suggesting that in garlic, the S-oxygenation of alliin biosynthetic intermediates primarily occurs after deglutamylation. The transient expression of green fluorescent protein (GFP) fusion proteins indicated that AsFMO1 is localized in the cytosol. AsFMO1 mRNA was accumulated in storage leaves of pre-emergent nearly sprouting bulbs, and in various tissues of sprouted bulbs with green foliage leaves. Taken together, our results suggest that AsFMO1 functions as an S-allyl-l-cysteine S-oxygenase, and contributes to the production of alliin both through the conversion of stored γ-glutamyl-S-allyl-l-cysteine to alliin in storage leaves during sprouting and through the de novo biosynthesis of alliin in green foliage leaves. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

  11. Validação interlaboratorial do teste de polarização fluorescente para o diagnóstico sorológico da brucelose bovina Interlaboratorial validation of the fluorescence polarization assay for the serodiagnosis of bovine brucellosis

    Directory of Open Access Journals (Sweden)

    Luis Antonio Mathias

    2010-10-01

    Full Text Available Esta investigação teve por objetivo validar o teste de polarização fluorescente (TPF para o diagnóstico sorológico da brucelose bovina, determinando a sensibilidade (SE e a especificidade relativas (SP e verificando a reprodutibilidade do teste em quatro laboratórios no Brasil. Foram selecionadas 1.389 amostras de soro sanguíneo, as quais foram inicialmente submetidas aos testes do antígeno acidificado tamponado (AAT e mercaptoetanol (2-ME. As mesmas amostras foram submetidas à reação de fixação de complemento (RFC e ao TPF. Para a avaliação do TPF, foi adotada a combinação dos resultados do AAT, da RFC e do 2-ME, utilizados como população de referência (padrão-ouro. Para a determinação do ponto de corte do TPF que proporciona a melhor combinação de sensibilidade e especificidade, foi usada a análise TG-ROC. A concordância entre os resultados dos quatro laboratórios foi determinada com base no indicador kappa e no coeficiente de correlação de Pearson. Os pontos de corte do TPF situaram-se entre 85,2 e 93,6 mP, conforme o laboratório. A sensibilidade variou de 91,7 a 97,3%, e a especificidade situou-se na faixa de 82,6 a 98,3%. Na comparação entre os resultados do TPF dos quatro laboratórios, o indicador kappa ficou entre 0,69 e 0,95, o que indica, na maioria das situações, reprodutibilidade excelente, e o coeficiente de correlação variou entre 0,76 e 0,99. Os resultados indicaram que o TPF apresentou bom desempenho, na maioria das situações, com sensibilidade e especificidade elevadas. Em comparação com os testes convencionais, o TPF apresenta as vantagens de ser de execução mais rápida e mais fácil e não estar sujeito à ocorrência de prozona, como a RFC e o 2-ME, nem de atividade anticomplementar, como a RFC.The purpose of this research was the interlaboratorial validation of the polarization fluorescence assay (PFA for the serodiagnosis of bovine brucellosis, verifying the relative sensitivity

  12. Cysteine Biosynthesis Controls Serratia marcescens Phospholipase Activity.

    Science.gov (United States)

    Anderson, Mark T; Mitchell, Lindsay A; Mobley, Harry L T

    2017-08-15

    Serratia marcescens causes health care-associated opportunistic infections that can be difficult to treat due to a high incidence of antibiotic resistance. One of the many secreted proteins of S. marcescens is the PhlA phospholipase enzyme. Genes involved in the production and secretion of PhlA were identified by screening a transposon insertion library for phospholipase-deficient mutants on phosphatidylcholine-containing medium. Mutations were identified in four genes ( cyaA , crp , fliJ , and fliP ) that are involved in the flagellum-dependent PhlA secretion pathway. An additional phospholipase-deficient isolate harbored a transposon insertion in the cysE gene encoding a predicted serine O -acetyltransferase required for cysteine biosynthesis. The cysE requirement for extracellular phospholipase activity was confirmed using a fluorogenic phospholipase substrate. Phospholipase activity was restored to the cysE mutant by the addition of exogenous l-cysteine or O -acetylserine to the culture medium and by genetic complementation. Additionally, phlA transcript levels were decreased 6-fold in bacteria lacking cysE and were restored with added cysteine, indicating a role for cysteine-dependent transcriptional regulation of S. marcescens phospholipase activity. S. marcescens cysE mutants also exhibited a defect in swarming motility that was correlated with reduced levels of flhD and fliA flagellar regulator gene transcription. Together, these findings suggest a model in which cysteine is required for the regulation of both extracellular phospholipase activity and surface motility in S. marcescens IMPORTANCE Serratia marcescens is known to secrete multiple extracellular enzymes, but PhlA is unusual in that this protein is thought to be exported by the flagellar transport apparatus. In this study, we demonstrate that both extracellular phospholipase activity and flagellar function are dependent on the cysteine biosynthesis pathway. Furthermore, a disruption of cysteine

  13. Characteristics of volume polarization holography with linear polarization light

    Science.gov (United States)

    Zang, Jinliang; Wu, An'an; Liu, Ying; Wang, Jue; Lin, Xiao; Tan, Xiaodi; Shimura, Tsutomu; Kuroda, Kazuo

    2015-10-01

    Volume polarization holographic recording in phenanthrenequinone-doped poly(methyl methacrylate) (PQ-PMMA) photopolymer with linear polarized light is obtained. The characteristics of the volume polarization hologram are experimentally investigated. It is found that beyond the paraxial approximation the polarization states of the holographic reconstruction light are generally different from the signal light. Based on vector wave theoretical analyses and material properties, the special exposure condition for correctly holographic reconstruction is obtained and experimentally demonstrated.

  14. Organisation of the pantothenate (vitamin B5) biosynthesis pathway in higher plants.

    Science.gov (United States)

    Ottenhof, Harald H; Ashurst, Jennifer L; Whitney, Heather M; Saldanha, S Adrian; Schmitzberger, Florian; Gweon, Hyun Soon; Blundell, Tom L; Abell, Chris; Smith, Alison G

    2004-01-01

    Pantothenate (vitamin B5) is the precursor for the biosynthesis of the phosphopantetheine moiety of coenzyme A and acyl carrier protein, and is synthesised in Escherichia coli by four enzymic reactions. Ketopantoate hydroxymethyltransferase (KPHMT) and pantothenate synthetase (PtS) catalyse the first and last steps, respectively. Two genes encoding KPHMT and one for PtS were identified in the Arabidopsis thaliana genome, and cDNAs for all three genes were amplified by PCR. The cDNAs were able to complement their respective E. coli auxotrophs, demonstrating that they encoded functional enzymes. Subcellular localisation of the proteins was investigated using green fluorescent protein (GFP) fusions and confocal microscopy. The two KPHMT-GFP fusion proteins were targeted exclusively to mitochondria, whereas PtS-GFP was found in the cytosol. This implies that there must be transporters for pathway intermediates. KPHMT enzyme activity could be measured in purified mitochondria from both pea leaves and Arabidopsis suspension cultures. We investigated whether Arabidopsis encoded homologues of the remaining two pantothenate biosynthesis enzymes from E. coli, l-aspartate-alpha-decarboxylase (ADC) and ketopantoate reductase (KPR). No homologue of ADC could be identified using either conventional blast or searches with the program fugue in which the structure of the E. coli ADC was compared to all the annotated proteins in Arabidopsis. ADC also appears to be absent from the genome of the yeast, Saccharomyces cerevisiae, by the same criteria. In contrast, a putative Arabidopsis oxidoreductase with some similarity to KPR was identified with fugue.

  15. Identification of a Xylogalacturonan Xylosyltransferase Involved in Pectin Biosynthesis in Arabidopsis

    Energy Technology Data Exchange (ETDEWEB)

    Pauly, Markus; Sorensen, Susanne Oxenboll; Harholt, Jesper; Geshi, Naomi; Sakuragi, Yumiko; Moller, Isabel; Zandleven, Joris; Bernal, Adriana J.; Jensen, Niels Bjerg; Sorensen, Charlotte; Jensen, Jacob K.; Beldman, Gerrit; Willats, William G.T.; Scheller, Henrik

    2009-08-19

    Xylogalacturonan (XGA) is a class of pectic polysaccharide found in plant cell walls. The Arabidopsis thaliana locus At5g33290 encodes a predicted Type II membrane protein, and insertion mutants of the At5g33290 locus had decreased cell wall xylose. Immunological studies, enzymatic extraction of polysaccharides, monosaccharide linkage analysis, and oligosaccharide mass profiling were employed to identify the affected cell wall polymer. Pectic XGA was reduced to much lower levels in mutant than in wild-type leaves, indicating a role of At5g33290 in XGA biosynthesis. The mutated gene was designated xylogalacturonan deficient1 (xgd1). Transformation of the xgd1-1 mutant with the wild-type gene restored XGA to wild-type levels. XGD1 protein heterologously expressed in Nicotiana benthamiana catalyzed the transfer of xylose from UDP-xylose onto oligogalacturonides and endogenous acceptors. The products formed could be hydrolyzed with an XGA-specific hydrolase. These results confirm that the XGD1 protein is a XGA xylosyltransferase. The protein was shown by expression of a fluorescent fusion protein in N. benthamiana to be localized in the Golgi vesicles as expected for a glycosyltransferase involved in pectin biosynthesis.

  16. Membranes and Fluorescence microscopy

    DEFF Research Database (Denmark)

    Bagatolli, Luis

    2009-01-01

    Fluorescence spectroscopy-based techniques using conventional fluorimeters have been extensively applied since the late 1960s to study different aspects of membrane-related phenomena, i.e., mainly relating to lipid-lipid and lipid-protein (peptide) interactions. Even though fluorescence spectrosc......Fluorescence spectroscopy-based techniques using conventional fluorimeters have been extensively applied since the late 1960s to study different aspects of membrane-related phenomena, i.e., mainly relating to lipid-lipid and lipid-protein (peptide) interactions. Even though fluorescence...... spectroscopy approaches provide very valuable structurally and dynamically related information on membranes, they generally produce mean parameters from data collected on bulk solutions of many vesicles and lack direct information on the spatial organization at the level of single membranes, a quality that can...... be provided by microscopy-related techniques. In this chapter, I will attempt to summarize representative examples concerning how microscopy (which provides information on membrane lateral organization by direct visualization) and spectroscopy techniques (which provides information about molecular interaction...

  17. Fluorescence lifetime based bioassays

    Science.gov (United States)

    Meyer-Almes, Franz-Josef

    2017-12-01

    Fluorescence lifetime (FLT) is a robust intrinsic property and material constant of fluorescent matter. Measuring this important physical indicator has evolved from a laboratory curiosity to a powerful and established technique for a variety of applications in drug discovery, medical diagnostics and basic biological research. This distinct trend was mainly driven by improved and meanwhile affordable laser and detection instrumentation on the one hand, and the development of suitable FLT probes and biological assays on the other. In this process two essential working approaches emerged. The first one is primarily focused on high throughput applications employing biochemical in vitro assays with no requirement for high spatial resolution. The second even more dynamic trend is the significant expansion of assay methods combining highly time and spatially resolved fluorescence data by fluorescence lifetime imaging. The latter approach is currently pursued to enable not only the investigation of immortal tumor cell lines, but also specific tissues or even organs in living animals. This review tries to give an actual overview about the current status of FLT based bioassays and the wide range of application opportunities in biomedical and life science areas. In addition, future trends of FLT technologies will be discussed.

  18. Experiments with Fermilab polarized proton and polarized antiproton beams

    International Nuclear Information System (INIS)

    Yokosawa, A.

    1990-01-01

    We summarize activities concerning the Fermilab polarized beams. They include a brief description of the polarized-beam facility, measurements of beam polarization by polarimeters, asymmetry measurements in the π degree production at high p perpendicular and in the Λ (Σ degree), π ± , π degree production at large x F , and Δσ L (pp, bar pp) measurements. 18 refs

  19. NUCLEON POLARIZATION IN 3-BODY MODELS OF POLARIZED LI-6

    NARCIS (Netherlands)

    SCHELLINGERHOUT, NW; KOK, LP; COON, SA; ADAM, RM

    1993-01-01

    Just as He-3 --> can be approximately characterized as a polarized neutron target, polarized Li-6D has been advocated as a good isoscalar nuclear target for the extraction of the polarized gluon content of the nucleon. The original argument rests upon a presumed ''alpha + deuteron'' picture of Li-6,

  20. Actin polymerization drives polar growth in Arabidopsis root hair cells.

    Science.gov (United States)

    Vazquez, Luis Alfredo Bañuelos; Sanchez, Rosana; Hernandez-Barrera, Alejandra; Zepeda-Jazo, Isaac; Sánchez, Federico; Quinto, Carmen; Torres, Luis Cárdenas

    2014-01-01

    In plants, the actin cytoskeleton is a prime regulator of cell polarity, growth, and cytoplasmic streaming. Tip growth, as observed in root hairs, caulonema, and pollen tubes, is governed by many factors, including calcium gradients, exocytosis and endocytosis, reactive oxygen species, and the cytoskeleton. Several studies indicate that the polymerization of G-actin into F-actin also contributes to tip growth. The structure and function of F-actin within the apical dome is variable, ranging from a dense meshwork to sparse single filaments. The presence of multiple F-actin structures in the elongating apices of tip-growing cells suggests that this cytoskeletal array is tightly regulated. We recently reported that sublethal concentrations of fluorescently labeled cytochalasin could be used to visualize the distribution of microfilament plus ends using fluorescence microscopy, and found that the tip region of the growing root hair cells of a legume plant exhibits a clear response to the nodulation factors secreted by Rhizobium. (1) In this current work, we expanded our analysis using confocal microscopy and demonstrated the existence of highly dynamic fluorescent foci along Arabidopsis root hair cells. Furthermore, we show that the strongest fluorescence signal accumulates in the tip dome of the growing root hair and seems to be in close proximity to the apical plasma membrane. Based on these findings, we propose that actin polymerization within the dome of growing root hair cells regulates polar growth.

  1. Geomagnetic polarity transitions

    Science.gov (United States)

    Merrill, Ronald T.; McFadden, Phillip L.

    1999-05-01

    The top of Earth's liquid outer core is nearly 2900 km beneath Earth's surface, so we will never be able to observe it directly. This hot, dense, molten iron-rich body is continuously in motion and is the source of Earth's magnetic field. One of the most dynamic manifestations at Earth's surface of this fluid body is, perhaps, a reversal of the geomagnetic field. Unfortunately, the most recent polarity transition occurred at about 780 ka, so we have never observed a transition directly. It seems that a polarity transition spans many human lifetimes, so no human will ever witness the phenomenon in its entirety. Thus we are left with the tantalizing prospect that paleomagnetic records of polarity transitions may betray some of the secrets of the deep Earth. Certainly, if there are systematics in the reversal process and they can be documented, then this will reveal substantial information about the nature of the lowermost mantle and of the outer core. Despite their slowness on a human timescale, polarity transitions occur almost instantaneously on a geological timescale. This rapidity, together with limitations in the paleomagnetic recording process, prohibits a comprehensive description of any reversal transition both now and into the foreseeable future, which limits the questions that may at this stage be sensibly asked. The natural model for the geomagnetic field is a set of spherical harmonic components, and we are not able to obtain a reliable model for even the first few harmonic terms during a transition. Nevertheless, it is possible, in principle, to make statements about the harmonic character of a geomagnetic polarity transition without having a rigorous spherical harmonic description of one. For example, harmonic descriptions of recent geomagnetic polarity transitions that are purely zonal can be ruled out (a zonal harmonic does not change along a line of latitude). Gleaning information about transitions has proven to be difficult, but it does seem

  2. APD detectors for biological fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Mazeres, S.; Borrel, V.; Magenc, C.; Courrech, J.L.; Bazer-Bachi, R.

    2006-01-01

    Fluorescence spectroscopy is a very convenient and widely used method for studying the molecular background of biological processes [L. Salome, J.L. Cazeil, A. Lopez, J.F. Tocanne, Eur. Biophys. J. 27 (1998) 391-402]. Chromophores are included in the structure under study and a flash of laser light induces fluorescence (Fluorescence Recovery After Photo-bleaching), the decay of which yields information on the polarity, the speed of rotation, and the speed of diffusion as well as on the temporal and spatial evolution of interactions between molecular species. The method can even be used to study living cells [J.F. Tocanne, L. Cezanne, A. Lopez, Prog. Lipid Res. 33 (1994) 203-237, L. Cezanne, A. Lopez, F. Loste, G. Parnaud, O. Saurel, P. Demange, J.F. Tocanne, Biochemistry 38 (1999) 2779-2786]. This is classically performed with a PM-based system. For biological reasons a decrease of the excitation of the cells is highly desirable. Because the fluorescence response then becomes fainter a significant improvement in detector capability would be welcome. We present here results obtained with an Avalanche Photo Diode (APD)-based system. The small sensitive area of detection allows a very significant improvement in signal/noise ratio, improvement in gain, and the opening-up of a new parameter space. With these new detectors we can begin the study of information transmission between cells through morphine receptors. This work involves both electronics engineers and biophysicists, so results and techniques in both fields will be presented here

  3. Statistical filtering in fluorescence microscopy and fluorescence correlation spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Macháň, Radek; Kapusta, Peter; Hof, Martin

    Roč. 406 , č. 20 (2014), s. 4797-4813 ISSN 1618-2642 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388955 Keywords : Filtered fluorescence correlation spectroscopy * Fluorescence lifetime correlation spectroscopy * Fluorescence spectral correlation spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.436, year: 2014

  4. Three Principles of Diversity-Generating Biosynthesis.

    Science.gov (United States)

    Gu, Wenjia; Schmidt, Eric W

    2017-10-17

    Natural products are significant therapeutic agents and valuable drug leads. This is likely owing to their three-dimensional structural complexity, which enables them to form complex interactions with biological targets. Enzymes from natural product biosynthetic pathways show great potential to generate natural product-like compounds and libraries. Many challenges still remain in biosynthesis, such as how to rationally synthesize small molecules with novel structures and how to generate maximum chemical diversity. In this Account, we describe recent advances from our laboratory in the synthesis of natural product-like libraries using natural biosynthetic machinery. Our work has focused on the pat and tru biosynthetic pathways to patellamides, trunkamide, and related compounds from cyanobacterial symbionts in marine tunicates. These belong to the cyanobactin class of natural products, which are part of the larger group of ribosomally synthesized and post-translationally modified peptides (RiPPs). These results have enabled the synthesis of rationally designed small molecules and libraries covering more than 1 million estimated derivatives. Because the RiPPs are translated on the ribosome and then enzymatically modified, they are highly compatible with recombinant technologies. This is important because it means that the resulting natural products, their derivatives, and wholly new compounds can be synthesized using the tools of genetic engineering. The RiPPs also represent possibly the most widespread group of bioactive natural products, although this is in part because of the broad definition of what constitutes a RiPP. In addition, the underlying ideas may form the basis for broad-substrate biosynthetic pathways beyond the RiPPs. For example, some of the ideas about kinetic ordering of broad substrate pathways may apply to polyketide or nonribosomal peptide biosynthesis as well. While making these products, we have sought to understand what makes biosynthetic

  5. Polyamine biosynthesis during germination of yeast ascospores.

    Science.gov (United States)

    Brawley, J V; Ferro, A J

    1979-01-01

    The role of the diamine putrescine during germination and outgrowth of ascospores of Saccharomyces cerevisiae was examined. Ornithine decarboxylase activity increased and declined rapidly during germination and outgrowth; peak activity was attained after the cells had proceeded through the G1 interval of the cell cycle, whereas minimal activity was present at the completion of the first cell division. alpha-Methylornithine inhibited both ornithine decarboxylase activity and the in vivo accumulation of putrescine. In the presence of alpha-methylornithireak dormancy and proceed through one cell division. Subsequent cellular growth, however, was retarded but not completely inhibited. The supplementation of Methylglyoxal bis(guanylhydrazone) to sporulation medium greatly inhibited this sexual process. These data suggest that the synthesis of putrescine is not required for the breaking of spore dormancy, but that polyamine biosynthesis may be essential for meiosis and sporulation. PMID:387744

  6. Biosynthesis and function of plant lipids

    International Nuclear Information System (INIS)

    Thomson, W.W.; Mudd, J.B.; Gibbs, M.

    1983-01-01

    The Sixth Annual Symposium in Botany and Plant Physiology was held January 13-15, 1983, at the University of California, Riverside. This volume comprises the papers that were presented. Subjects discussed at the symposium covered a wide range in the field of plant lipids. Biosynthesis of lipids occupied an important fraction of the presentations at the symposium. Subjects included detailed studies of the enzymes of fatty acid synthesis, several discussions of the incorporation of fatty acids into glycerolipids and the further modification of the fatty acids, and the synthesis of glycerolipids and desaturation of fatty acids in both maturing oilseeds and chloroplasts. The physicochemical studies of glycerolipids and sterols in artificial membranes have led to distinct conclusions about their behaviour which must be relevant in the biological membrane. Results on the functional consequences of modifying the galactolipid composition in the chloroplast were an encouraging sign of progress in the attempts to relate membrane lipid composition to physiological function

  7. Biosurfactant Mediated Biosynthesis of Selected Metallic Nanoparticles

    Science.gov (United States)

    Płaza, Grażyna A.; Chojniak, Joanna; Banat, Ibrahim M.

    2014-01-01

    Developing a reliable experimental protocol for the synthesis of nanomaterials is one of the challenging topics in current nanotechnology particularly in the context of the recent drive to promote green technologies in their synthesis. The increasing need to develop clean, nontoxic and environmentally safe production processes for nanoparticles to reduce environmental impact, minimize waste and increase energy efficiency has become essential in this field. Consequently, recent studies on the use of microorganisms in the synthesis of selected nanoparticles are gaining increased interest as they represent an exciting area of research with considerable development potential. Microorganisms are known to be capable of synthesizing inorganic molecules that are deposited either intra- or extracellularly. This review presents a brief overview of current research on the use of biosurfactants in the biosynthesis of selected metallic nanoparticles and their potential importance. PMID:25110864

  8. Terpenoids and Their Biosynthesis in Cyanobacteria

    Directory of Open Access Journals (Sweden)

    Bagmi Pattanaik

    2015-01-01

    Full Text Available Terpenoids, or isoprenoids, are a family of compounds with great structural diversity which are essential for all living organisms. In cyanobacteria, they are synthesized from the methylerythritol-phosphate (MEP pathway, using glyceraldehyde 3-phosphate and pyruvate produced by photosynthesis as substrates. The products of the MEP pathway are the isomeric five-carbon compounds isopentenyl diphosphate and dimethylallyl diphosphate, which in turn form the basic building blocks for formation of all terpenoids. Many terpenoid compounds have useful properties and are of interest in the fields of pharmaceuticals and nutrition, and even potentially as future biofuels. The MEP pathway, its function and regulation, and the subsequent formation of terpenoids have not been fully elucidated in cyanobacteria, despite its relevance for biotechnological applications. In this review, we summarize the present knowledge about cyanobacterial terpenoid biosynthesis, both regarding the native metabolism and regarding metabolic engineering of cyanobacteria for heterologous production of non-native terpenoids.

  9. Terpenoids and Their Biosynthesis in Cyanobacteria

    Science.gov (United States)

    Pattanaik, Bagmi; Lindberg, Pia

    2015-01-01

    Terpenoids, or isoprenoids, are a family of compounds with great structural diversity which are essential for all living organisms. In cyanobacteria, they are synthesized from the methylerythritol-phosphate (MEP) pathway, using glyceraldehyde 3-phosphate and pyruvate produced by photosynthesis as substrates. The products of the MEP pathway are the isomeric five-carbon compounds isopentenyl diphosphate and dimethylallyl diphosphate, which in turn form the basic building blocks for formation of all terpenoids. Many terpenoid compounds have useful properties and are of interest in the fields of pharmaceuticals and nutrition, and even potentially as future biofuels. The MEP pathway, its function and regulation, and the subsequent formation of terpenoids have not been fully elucidated in cyanobacteria, despite its relevance for biotechnological applications. In this review, we summarize the present knowledge about cyanobacterial terpenoid biosynthesis, both regarding the native metabolism and regarding metabolic engineering of cyanobacteria for heterologous production of non-native terpenoids. PMID:25615610

  10. A Molecular Description of Cellulose Biosynthesis

    Science.gov (United States)

    McNamara, Joshua T.; Morgan, Jacob L.W.; Zimmer, Jochen

    2016-01-01

    Cellulose is the most abundant biopolymer on Earth, and certain organisms from bacteria to plants and animals synthesize cellulose as an extracellular polymer for various biological functions. Humans have used cellulose for millennia as a material and an energy source, and the advent of a lignocellulosic fuel industry will elevate it to the primary carbon source for the burgeoning renewable energy sector. Despite the biological and societal importance of cellulose, the molecular mechanism by which it is synthesized is now only beginning to emerge. On the basis of recent advances in structural and molecular biology on bacterial cellulose synthases, we review emerging concepts of how the enzymes polymerize glucose molecules, how the nascent polymer is transported across the plasma membrane, and how bacterial cellulose biosynthesis is regulated during biofilm formation. Additionally, we review evolutionary commonalities and differences between cellulose synthases that modulate the nature of the cellulose product formed. PMID:26034894

  11. Biosurfactant Mediated Biosynthesis of Selected Metallic Nanoparticles

    Directory of Open Access Journals (Sweden)

    Grażyna A. Płaza

    2014-08-01

    Full Text Available Developing a reliable experimental protocol for the synthesis of nanomaterials is one of the challenging topics in current nanotechnology particularly in the context of the recent drive to promote green technologies in their synthesis. The increasing need to develop clean, nontoxic and environmentally safe production processes for nanoparticles to reduce environmental impact, minimize waste and increase energy efficiency has become essential in this field. Consequently, recent studies on the use of microorganisms in the synthesis of selected nanoparticles are gaining increased interest as they represent an exciting area of research with considerable development potential. Microorganisms are known to be capable of synthesizing inorganic molecules that are deposited either intra- or extracellularly. This review presents a brief overview of current research on the use of biosurfactants in the biosynthesis of selected metallic nanoparticles and their potential importance.

  12. Polarized electron beams at SLAC

    International Nuclear Information System (INIS)

    Moffeit, K.C.

    1992-11-01

    SLAC has successfully accelerated high energy polarized electrons for the Stanford Linear Collider and fixed polarized nuclear target experiments. The polarized electron beams at SLAC use a gallium arsenide (GaAlAs for E-142) photon emission source to provide the beam of polarized electrons with polarization of approximately 28% (41% for E-142). While the beam emittance is reduced in the damping ring for SLC operation a system of bend magnets and superconducting solenoids preserve and orient the spin direction for maximum longitudinal polarization at the collision point. The electron polarization is monitored with a Compton scattering polarimeter, and was typically 22% at the e+e- collision point for the 1992 run. Improvements are discussed to increase the source polarization and to reduce the depolarization effects between the source and the collision point

  13. Analytical polarization calculations beyond SLIM

    International Nuclear Information System (INIS)

    Barber, D.P.

    1989-01-01

    A comparison is made between the theories of Bell and Leinaas and of Derbenev and Kondratenko for the spin polarization in electron storage rings. A calculation of polarization in HERA using the program SMILE of Mane is presented

  14. Acylphloroglucinol Biosynthesis in Strawberry Fruit1

    Science.gov (United States)

    Song, Chuankui; Ring, Ludwig; Hoffmann, Thomas; Huang, Fong-Chin; Slovin, Janet; Schwab, Wilfried

    2015-01-01

    Phenolics have health-promoting properties and are a major group of metabolites in fruit crops. Through reverse genetic analysis of the functions of four ripening-related genes in the octoploid strawberry (Fragaria × ananassa), we discovered four acylphloroglucinol (APG)-glucosides as native Fragaria spp. fruit metabolites whose levels were differently regulated in the transgenic fruits. The biosynthesis of the APG aglycones was investigated by examination of the enzymatic properties of three recombinant Fragaria vesca chalcone synthase (FvCHS) proteins. CHS is involved in anthocyanin biosynthesis during ripening. The F. vesca enzymes readily catalyzed the condensation of two intermediates in branched-chain amino acid metabolism, isovaleryl-Coenzyme A (CoA) and isobutyryl-CoA, with three molecules of malonyl-CoA to form phlorisovalerophenone and phlorisobutyrophenone, respectively, and formed naringenin chalcone when 4-coumaroyl-CoA was used as starter molecule. Isovaleryl-CoA was the preferred starter substrate of FvCHS2-1. Suppression of CHS activity in both transient and stable CHS-silenced fruit resulted in a substantial decrease of APG glucosides and anthocyanins and enhanced levels of volatiles derived from branched-chain amino acids. The proposed APG pathway was confirmed by feeding isotopically labeled amino acids. Thus, Fragaria spp. plants have the capacity to synthesize pharmaceutically important APGs using dual functional CHS/(phloriso)valerophenone synthases that are expressed during fruit ripening. Duplication and adaptive evolution of CHS is the most probable scenario and might be generally applicable to other plants. The results highlight that important promiscuous gene function may be missed when annotation relies solely on in silico analysis. PMID:26169681

  15. Who's who in fluorescence 2008

    CERN Document Server

    Geddes, Chris D

    2008-01-01

    The Journal of Fluorescence's sixth Who's Who directory publishes the names, contact details, specialty keywords, and a brief description of scientists employing fluorescence methodology and instrumentation in their working lives. This is a unique reference.

  16. Proceedings of the Japan-US workshop on plasma polarization spectroscopy and the fourth international symposium on plasma polarization spectroscopy

    International Nuclear Information System (INIS)

    Fujimoto, Takashi; Beiersdorfer, Peter

    2004-07-01

    The international meeting on Plasma Polarization Spectroscopy (PPS) was held at Kyoto University during February 4-6, 2004. This Proceedings book includes the summaries of the talks given in that meeting. Starting with the Overview talk by Csanak, the subjects cover: x-ray polarization experiments on z-pinches (plasma foci), and an x-pinch, a laser-produced plasma in a gas atmosphere, an interpretation of the polarized 1<- 0 x-ray laser line, polarization observation from various laser-produced plasmas including a recombining phase plasma, a report on the on-going project of a laser facility, several polarization observations on magnetically confined plasmas including the Large Helical Device and an ECR plasma, a new laser-induced fluorescence diagnostic method. On atomic physics side given are: various polarization measurements on EBIT, precision spectroscopy on the TEXTOR, user-friendly atomic codes. Instrumentation is also a subject of this book. The 18 of the presented papers are indexed individually. (J.P.N.)

  17. On Determinants of Political Polarization

    OpenAIRE

    Grechyna, Daryna

    2015-01-01

    Political polarization has been shown to significantly influence a country's economic performance. However, little is known about the drivers of political polarization. In this article, we aim to identify the main determinants of political polarization using Bayesian Model Averaging to overcome the problem of model uncertainty. We find that the level of trust within a country and the degree of income inequality are the most robust determinants of political polarization.

  18. Polarized electrogowdy spacetimes censored

    Energy Technology Data Exchange (ETDEWEB)

    Nungesser, Ernesto, E-mail: ernesto.nungesser@aei.mpg.d [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Am Muehlenberg 1, 14476 Potsdam (Germany)

    2010-05-01

    A sketch of the proof of strong cosmic censorship is presented for a class of solutions of the Einstein-Maxwell equations, those with polarized Gowdy symmetry. A key element of the argument is the observation that by means of a suitable choice of variables the central equations in this problem can be written in a form where they are identical to the central equations for general (i.e. non-polarized) vacuum Gowdy spacetimes. Using this it is seen that the results of Ringstroem on strong cosmic censorship in the vacuum case have implications for the Einstein-Maxwell case. Working out the geometrical meaning of these analytical results leads to the main conclusion.

  19. PEPPo: Using a Polarized Electron Beam to Produce Polarized Positrons

    Energy Technology Data Exchange (ETDEWEB)

    Adeyemi, Adeleke H. [Hampton Univ., Hampton, VA (United States); et al.

    2015-09-01

    Polarized positron beams have been identified as either an essential or a significant ingredient for the experimental program of both the present and next generation of lepton accelerators (JLab, Super KEK B, ILC, CLIC). An experiment demonstrating a new method for producing polarized positrons has been performed at the Continuous Electron Beam Accelerator Facility at Jefferson Lab. The PEPPo (Polarized Electrons for Polarized Positrons) concept relies on the production of polarized e⁻/e⁺ pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high-Z conversion target. PEPPo demonstrated the effective transfer of spin-polarization of an 8.2 MeV/c polarized (P~85%) electron beam to positrons produced in varying thickness tungsten production targets, and collected and measured in the range of 3.1 to 6.2 MeV/c. In comparison to other methods this technique reveals a new pathway for producing either high-energy or thermal polarized positron beams using a relatively low polarized electron beam energy (~10MeV) .This presentation will describe the PEPPo concept, the motivations of the experiment and high positron polarization achieved.

  20. Polarization induced doped transistor

    Science.gov (United States)

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  1. Polar bears, Ursus maritimus

    Science.gov (United States)

    Rode, Karyn D.; Stirling, Ian

    2017-01-01

    Polar bears are the largest of the eight species of bears found worldwide and are covered in a pigment-free fur giving them the appearance of being white. They are the most carnivorous of bear species consuming a high-fat diet, primarily of ice-associated seals and other marine mammals. They range throughout the circumpolar Arctic to the southernmost extent of seasonal pack ice.

  2. Polarized advanced fuel reactors

    International Nuclear Information System (INIS)

    Kulsrud, R.M.

    1987-07-01

    The d- 3 He reaction has the same spin dependence as the d-t reaction. It produces no neutrons, so that if the d-d reactivity could be reduced, it would lead to a neutron-lean reactor. The current understanding of the possible suppression of the d-d reactivity by spin polarization is discussed. The question as to whether a suppression is possible is still unresolved. Other advanced fuel reactions are briefly discussed. 11 refs

  3. On polarization in biomembranes

    DEFF Research Database (Denmark)

    Zecchi, Karis Amata

    close to physiological conditions, making these effects biologically relevant. In this work, we consider the case of asymmetric membranes which can display spontaneous polarization in the absence of a field. Close to the phase transition, we find that the membrane displays piezoelectric, flexoelectric...... on different geometries point in the direction of a flexoelectric mechanism behind current rectification in lipid bilayers. Finally, we suggest that our updated equivalent circuit should be included in the interpretation of elctrophysiological data....

  4. Multifrequency Behaviour of Polars

    Directory of Open Access Journals (Sweden)

    K. Reinsch

    2015-02-01

    Full Text Available Cataclysmic variables emit over a wide range of the electromagnetic spectrum. In this paper I will review observations of polars in relevant passbands obtained during the last decade and will discuss their diagnostical potential to access the physics of the main components within the binary systems. This will include a discussion of intrinsic source variability and the quest for simultaneous multi-frequency observations.

  5. Who's who in fluorescence 2005

    CERN Document Server

    Geddes, Chris D

    2006-01-01

    The Journal of Fluorescence's third Who's Who directory publishes the names, contact details, specialty keywords, photographs, and a brief description of scientists employing fluorescence methodology and instrumentation in their working livesThe directory provides company contact details with a brief list of fluorescence-related products.

  6. Image calibration in fluorescence microscopy.

    NARCIS (Netherlands)

    Zwier, J.M.; van Rooij, G.J.; Hofstraat, J.W.; Brakenhoff, G.J.

    2004-01-01

    A fluorescence image calibration method is presented based on the use of standardized uniformly fluorescing reference layers. It is demonstrated to be effective for the correction of non-uniform imaging characteristics across the image (shading correction) as well as for relating fluorescence

  7. Fluorescence spectroscopy of dental calculus

    International Nuclear Information System (INIS)

    Bakhmutov, D; Gonchukov, S; Sukhinina, A

    2010-01-01

    The aim of the present study was to investigate the fluorescence properties of dental calculus in comparison with the properties of adjacent unaffected tooth structure using both lasers and LEDs in the UV-visible range for fluorescence excitation. The influence of calculus color on the informative signal is demonstrated. The optimal spectral bands of excitation and registration of the fluorescence are determined

  8. Fluorescence depolarization as a probe of molecular dynamics within liquid jets

    Science.gov (United States)

    Kenyon, A. J.; McCaffery, A. J.; Quintella, C. M.

    Preliminary results are presented from a study of fluorescence depolarization within a thin laminar jet of rhodamine 6 G in ethylene glycol. A large number of polarization measurements taken across the jet have enabled us to build up a detailed polarization map of the liquid flow. Relating the degree of depolarization to molecular alignment caused by the presence of shear forces within the jet, we propose that this method may be used as a sensitive probe of the molecular dynamics of liquid flow.

  9. Polar Business Design

    Directory of Open Access Journals (Sweden)

    Sébastien Caisse

    2014-02-01

    Full Text Available Polar business design aims to enable entrepreneurs, managers, consultants, researchers, and business students to better tackle model-based analysis, creation, and transformation of businesses, ventures, and, more generically, collective endeavors of any size and purpose. It is based on a systems-thinking approach that builds on a few interrelated core concepts to create holistic visual frameworks. These core concepts act as poles linked by meaningful dyads, flows, and faces arranged in geometric shapes. The article presents two such polar frameworks as key findings in an ongoing analytic autoethnography: the three-pole Value−Activity−Stakeholder (VAS triquetra and the four-pole Offer−Creation−Character−Stakeholder (OCCS tetrahedron. The VAS triquetra is a more aggregated model of collective endeavors. The OCCS tetrahedron makes a trade-off between a steeper learning curve and deeper, richer representation potential. This article discusses how to use these two frameworks as well as their limits, and explores the potential that polar business design offers for future research.

  10. Dual-wavelength excitation to reduce background fluorescence for fluorescence spectroscopic quantitation of erythrocyte zinc protoporphyrin-IX and protoporphyrin-IX from whole blood and oral mucosa

    Science.gov (United States)

    Hennig, Georg; Vogeser, Michael; Holdt, Lesca M.; Homann, Christian; Großmann, Michael; Stepp, Herbert; Gruber, Christian; Erdogan, Ilknur; Hasmüller, Stephan; Hasbargen, Uwe; Brittenham, Gary M.

    2014-02-01

    Erythrocyte zinc protoporphyrin-IX (ZnPP) and protoporphyrin-IX (PPIX) accumulate in a variety of disorders that restrict or disrupt the biosynthesis of heme, including iron deficiency and various porphyrias. We describe a reagent-free spectroscopic method based on dual-wavelength excitation that can measure simultaneously both ZnPP and PPIX fluorescence from unwashed whole blood while virtually eliminating background fluorescence. We further aim to quantify ZnPP and PPIX non-invasively from the intact oral mucosa using dual-wavelength excitation to reduce the strong tissue background fluorescence while retaining the faint porphyrin fluorescence signal originating from erythrocytes. Fluorescence spectroscopic measurements were made on 35 diluted EDTA blood samples using a custom front-face fluorometer. The difference spectrum between fluorescence at 425 nm and 407 nm excitation effectively eliminated background autofluorescence while retaining the characteristic porphyrin peaks. These peaks were evaluated quantitatively and the results compared to a reference HPLC-kit method. A modified instrument using a single 1000 μm fiber for light delivery and detection was used to record fluorescence spectra from oral mucosa. For blood measurements, the ZnPP and PPIX fluorescence intensities from the difference spectra correlated well with the reference method (ZnPP: Spearman's rho rs = 0.943, p ZnPP/heme and PPIX/heme ratios from unwashed whole blood, simplifying clinical laboratory measurements. The difference technique reduces the background fluorescence from measurements on oral mucosa, allowing for future non-invasive quantitation of erythrocyte ZnPP and PPIX.

  11. M2 polarization enhances silica nanoparticle uptake by macrophages

    Directory of Open Access Journals (Sweden)

    Jessica eHoppstädter

    2015-03-01

    Full Text Available While silica nanoparticles have enabled numerous industrial and medical applications, their toxicological safety requires further evaluation. Macrophages are the major cell population responsible for nanoparticle clearance in vivo. The prevailing macrophage phenotype largely depends on the local immune status of the host. Whereas M1-polarized macrophages are considered as pro-inflammatory macrophages involved in host defense, M2 macrophages exhibit anti-inflammatory and wound-healing properties, but also promote tumor growth.We employed different models of M1 and M2 polarization: GM-CSF/LPS/IFN-gamma was used to generate primary human M1 cells and M-CSF/IL-10 to differentiate M2 monocyte-derived macrophages. PMA-differentiated THP-1 cells were polarized towards an M1 type by LPS/IFN-gamma and towards M2 by IL-10. Uptake of fluorescent silica nanoparticles (Ø 26 and 41 nm and microparticles (Ø 1.75 µm was quantified. At the concentration used (50 µg/ml, silica nanoparticles did not influence cell viability as assessed by MTT assay. Nanoparticle uptake was enhanced in M2-polarized primary human monocyte-derived macrophages compared with M1 cells, as shown by flow cytometric and microscopic approaches. In contrast, the uptake of microparticles did not differ between M1 and M2 phenotypes. M2 polarization was also associated with increased nanoparticle uptake in the macrophage-like THP-1 cell line. In accordance, in vivo polarized M2-like primary human tumor-associated macrophages (TAM obtained from lung tumors took up more nanoparticles than M1-like alveolar macrophages isolated from the surrounding lung tissue.In summary, our data indicate that the M2 polarization of macrophages promotes nanoparticle internalization. Therefore, the phenotypical differences between macrophage subsets should be taken into consideration in future investigations on nanosafety, but might also open up therapeutic perspectives allowing to specifically target M2

  12. Spectroscopic characterization of novel fluorescent lipid membrane probes

    International Nuclear Information System (INIS)

    Knapp, M.

    2001-11-01

    The aim of this thesis was the spectroscopic characterization of new, so far not described fluorescence markers which incorporate into ordered systems and provide information about their structure, the phase transition and aggregation. Bianthryl, Anthracen and Coumarin 6 were incorporated into liposomes formed from Lecithine, DMPC or DPPC as well as β-Cyclodextrin. The systems were characterized by means of classical-spectroscopic methods, laser-induced fluorescence and fluorescence correlation spectroscopy (FCS). Because of the prospective phyto-physical characteristics of bianthryl, i.e. the formation of a charge-separated electronic exited state this probe is particularly suitable to detect small changes of micro viscosity and local polarity of liposomes. Due to three clearly separated fluorescence lifetimes of the excited singlet state, measured for Bianthryl, three specific sites of this molecule within the phospholipid membrane were proven. Coumarin 6 incorporates likewise very well in Liposomes. The thermotrope phase transition at temperature 24,5 o C is well provable by the change of the anisotropy of fluorescence of this laser dye. By time-resolved anisotropy measurements the dynamics (rotation) was proven with high sensitivity. The thermotropic phase transition of DMPC Liposomes was detected by means of fluorescence reasonance energy transfer (FRET). A specific method for the determination of fluorescence quantum yields in strongly scattering solutions was suggested on the basis of FRET using Anthracen as energy donor and coumarin 6 as energy acceptor. For the energy transfer of Anthracen to Coumarin 6 in the gel phase of the DMPC liposomes as substantial proportion of static transfer was found. The presence of correlated donor-acceptor pairs was proven by the comparison of stationary and time-resolved fluorescence. Further more, concentration- and temperature dependent formation was found of anthracene dimers. Such dimers are formed in the gel phase of

  13. Fluorescent quantification of melanin

    OpenAIRE

    Fernandes, Bruno Pacheco; Matamá, Maria Teresa; Guimarães, Diana Isabel Pereira; Gomes, Andreia; Cavaco-Paulo, Artur

    2016-01-01

    Melanin quantification is reportedly performed by absorption spectroscopy, commonly at 405 nm. Here, we propose the implementation of fluorescence spectroscopy for melanin assessment. In a typical in vitro assay to assess melanin production in response to an external stimulus, absorption spectroscopy clearly overvalues melanin content. This method is also incapable of distinguishing non-melanotic/amelanotic control cells from those that are actually capable of performing melanogenesis. Theref...

  14. Loss of ferulate 5-hydroxylase leads to Mediator-dependent inhibition of soluble phenylpropanoid biosynthesis in Arabidopsis

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Nickolas; Bonawitz, Nicholas D.; Nyffeler, Kayleigh E.; Chapple, Clint

    2015-06-05

    Phenylpropanoids are phenylalanine-derived specialized metabolites and include important structural components of plant cell walls, such as lignin and hydroxycinnamic acids, as well as ultraviolet and visible light-absorbing pigments, such as hydroxycinnamate esters (HCEs) and anthocyanins. Previous work has revealed a remarkable degree of plasticity in HCE biosynthesis, such that most Arabidopsis (Arabidopsis thaliana) mutants with blockages in the pathway simply redirect carbon flux to atypical HCEs. In contrast, the ferulic acid hydroxylase1 (fah1) mutant accumulates greatly reduced levels of HCEs, suggesting that phenylpropanoid biosynthesis may be repressed in response to the loss of FERULATE 5-HYDROXYLASE (F5H) activity. Here, we show that in fah1 mutant plants, the activity of HCE biosynthetic enzymes is not limiting for HCE accumulation, nor is phenylpropanoid flux diverted to the synthesis of cell wall components or flavonol glycosides. We further show that anthocyanin accumulation is also repressed in fah1 mutants and that this repression is specific to tissues in which F5H is normally expressed. Finally, we show that repression of both HCE and anthocyanin biosynthesis in fah1 mutants is dependent on the MED5a/5b subunits of the transcriptional coregulatory complex Mediator, which are similarly required for the repression of lignin biosynthesis and the stunted growth of the phenylpropanoid pathway mutant reduced epidermal fluorescence8. Taken together, these observations show that the synthesis of HCEs and anthocyanins is actively repressed in a MEDIATOR-dependent manner in Arabidopsis fah1 mutants and support an emerging model in which MED5a/5b act as central players in the homeostatic repression of phenylpropanoid metabolism.

  15. Polarized spectroscopic properties of Nd3+-doped KGd(WO4)2 single crystal

    International Nuclear Information System (INIS)

    Chen Yujin; Lin Yanfu; Gong Xinghong; Tan Qiguang; Zhuang Jian; Luo Zundu; Huang Yidong

    2007-01-01

    The polarized absorption spectra, infrared fluorescence spectra, upconversion visible fluorescence spectra, and fluorescence decay curve of orientated Nd 3+ :KGd(WO 4 ) 2 crystal were measured at room-temperature. Some important spectroscopic parameters were investigated in detail in the framework of the Judd-Ofelt theory and the Fuchtbauer-Ladenburg formula. The effect of the crystal structure on the spectroscopic properties of the Nd 3+ ions was analyzed. The relation among the spectroscopic parameters and the laser performances of the Nd 3+ :KGd(WO 4 ) 2 crystal was discussed

  16. First attempt of the measurement of the beam polarization at an accelerator with the optical electron polarimeter POLO

    CERN Document Server

    Collin, B; Essabaa, S; Frascaria, R; Gacougnolle, R; Kunne, Ronald Alexander; Aulenbacher, K; Tioukine, V

    2004-01-01

    The conventional methods for measuring the polarization of electron beams are either time consuming, invasive or accurate only to a few percent. We developped a method to measure electron beam polarization by observing the light emitted by argon atoms following their excitation by the impact of polarized electrons. The degree of circular polarization of the emitted fluorescence is directly related to the electron polarization. We tested the polarimeter on a test GaAs source available at the MAMI electron accelerator in Mainz, Germany. The polarimeter determines the polarization of a 50 keV electron beam decelerated to a few eV and interacting with an effusive argon gas jet. The resulting decay of the excited states produces the emission of a circularly polarized radiation line at 811.5 nm which is observed and analyzed.

  17. Engineering E. coli for caffeic acid biosynthesis from renewable sugars.

    Science.gov (United States)

    Zhang, Haoran; Stephanopoulos, Gregory

    2013-04-01

    Caffeic acid is a valuable aromatic compound that possesses many important pharmacological activities. In structure, caffeic acid belongs to the hydroxycinnamic acid family and can be biosynthesized from the aromatic amino acid tyrosine. In the present paper, the caffeic acid biosynthesis pathway was reconstituted in engineered Escherichia coli to produce caffeic acid from simple biomass sugar glucose and xylose. Different engineering approaches were utilized to optimize the production. Specifically, two parallel biosynthesis routes leading from tyrosine to caffeic acid were studied. The copy number of the intermediate biosynthesis genes was varied to find appropriate gene doses for caffeic acid biosynthesis. Three different media, including a MOPS medium, a synthetic medium, and a rich medium, were also examined to improve the production. The highest specific caffeic acid production achieved was 38 mg/L/OD. Lastly, cultivation of engineered E. coli in a bioreactor resulted in a production of 106 mg/L caffeic acid after 4 days.

  18. Stimulation of artemisinin biosynthesis in Artemisia annua hairy ...

    African Journals Online (AJOL)

    , the OGA-induced reactive oxygen species (ROS) were involved in stimulating the artemisinin biosynthesis in the hairy roots. This is the first report on the stimulation of artemisinin production in hairy roots by an oligogalacturonide elicitor.

  19. Biosynthesis, regulation and biological role of strigolactones in rice

    NARCIS (Netherlands)

    Moura Luis Cardoso, De C.S.

    2014-01-01

    In her thesis Catarina Cardoso studied strigolactone biosynthesis in rice. Strigolactones are multifunctional compounds produced by plants. They are plant hormones that regulate plant architecture, but in addition plants release strigolactones into the soil to communicate and initiate beneficial

  20. Naturally occurring fluorescence in frogs.

    Science.gov (United States)

    Taboada, Carlos; Brunetti, Andrés E; Pedron, Federico N; Carnevale Neto, Fausto; Estrin, Darío A; Bari, Sara E; Chemes, Lucía B; Peporine Lopes, Norberto; Lagorio, María G; Faivovich, Julián

    2017-04-04

    Fluorescence, the absorption of short-wavelength electromagnetic radiation reemitted at longer wavelengths, has been suggested to play several biological roles in metazoans. This phenomenon is uncommon in tetrapods, being restricted mostly to parrots and marine turtles. We report fluorescence in amphibians, in the tree frog Hypsiboas punctatus, showing that fluorescence in living frogs is produced by a combination of lymph and glandular emission, with pigmentary cell filtering in the skin. The chemical origin of fluorescence was traced to a class of fluorescent compounds derived from dihydroisoquinolinone, here named hyloins. We show that fluorescence contributes 18-29% of the total emerging light under twilight and nocturnal scenarios, largely enhancing brightness of the individuals and matching the sensitivity of night vision in amphibians. These results introduce an unprecedented source of pigmentation in amphibians and highlight the potential relevance of fluorescence in visual perception in terrestrial environments.

  1. NAD+ biosynthesis, aging, and disease [version 1; referees: 2 approved

    OpenAIRE

    Sean Johnson; Shin–ichiro Imai

    2018-01-01

    Nicotinamide adenine dinucleotide (NAD+) biosynthesis and its regulation have recently been attracting markedly increasing interest. Aging is marked by a systemic decrease in NAD+ across multiple tissues. The dysfunction of NAD+ biosynthesis plays a critical role in the pathophysiologies of multiple diseases, including age-associated metabolic disorders, neurodegenerative diseases, and mental disorders. As downstream effectors, NAD+-dependent enzymes, such as sirtuins, are involved in the pro...

  2. Standardization and quality assurance in fluorescence measurements I state-of-the art and future challenges

    CERN Document Server

    Resch-Genger, Ute

    2008-01-01

    The validation and standardization of fluorescence methods is still in its infancy as compared to other prominent analytical and bioanalytical methods. Appropriate quality assurance standards are however a prerequisite for applications in highly regulated fields such as medical diagnostics, drug development, or food analysis. For the first time, a team of recognized international experts has documented the present status of quality assurance in fluorescence measurements, and outlines concepts for establishing standards in this field. This first of two volumes covers basic aspects and various techniques such as steady-state and time-resolved fluorometry, polarization techniques, and fluorescent chemical sensors

  3. Structural and dynamical aspects of skin studied by multiphoton excitation fluorescence microscopy-based methods

    DEFF Research Database (Denmark)

    Bloksgaard, Maria; Brewer, Jonathan R.; Bagatolli, Luis

    2013-01-01

    -carboxyethyl)-5-(and-6)-carboxyfluorescein) and diffusion coefficients of distinct fluorescence probes (raster imaging correlation spectroscopy) can be obtained from different regions of the tissue. Comparative studies of different tissue strata, but also between equivalent regions of normal and abnormal......' parameters. Specifically, by applying these methods, spatially resolved maps of water dipolar relaxation (generalized polarization function using the 6-lauroyl-2-(N,N-dimethylamino)naphthale probe), activity of protons (fluorescence lifetime imaging using a proton sensitive fluorescence probe--2,7-bis-(2...

  4. Fenarimol, a Pyrimidine-Type Fungicide, Inhibits Brassinosteroid Biosynthesis

    Directory of Open Access Journals (Sweden)

    Keimei Oh

    2015-07-01

    Full Text Available The plant steroid hormone brassinosteroids (BRs are important signal mediators that regulate broad aspects of plant growth and development. With the discovery of brassinoazole (Brz, the first specific inhibitor of BR biosynthesis, several triazole-type BR biosynthesis inhibitors have been developed. In this article, we report that fenarimol (FM, a pyrimidine-type fungicide, exhibits potent inhibitory activity against BR biosynthesis. FM induces dwarfism and the open cotyledon phenotype of Arabidopsis seedlings in the dark. The IC50 value for FM to inhibit stem elongation of Arabidopsis seedlings grown in the dark was approximately 1.8 ± 0.2 μM. FM-induced dwarfism of Arabidopsis seedlings could be restored by brassinolide (BL but not by gibberellin (GA. Assessment of the target site of FM in BR biosynthesis by feeding BR biosynthesis intermediates indicated that FM interferes with the side chain hydroxylation of BR biosynthesis from campestanol to teasterone. Determination of the binding affinity of FM to purified recombinant CYP90D1 indicated that FM induced a typical type II binding spectrum with a Kd value of approximately 0.79 μM. Quantitative real-time PCR analysis of the expression level of the BR responsive gene in Arabidopsis seedlings indicated that FM induces the BR deficiency in Arabidopsis.

  5. Effect of fertilisation and harvest period on polar metabolites of Calendula oficcinalis

    Directory of Open Access Journals (Sweden)

    Eduardo Felipe Alves Fernandes

    Full Text Available The present study evaluated the chemical profile of polar extracts of Calendula officinalis L., Asteraceae, that were grown under different cultivation conditions: chemical fertilisation, organic fertilisation and mulching. Furthermore, we investigated metabolite variations during plant development by comparing the metabolites from harvested plants at 60 and 120 days after planting. We used HPLC-DAD-MS/MS to tentatively identify metabolites. In total, we identified seven known compounds: five flavonoid glycosides and two caffeoylquinic acids derivatives. There were no statistically significant differences in the expression of metabolites from plants grown under the examined soil treatments. However, five substances varied according to harvest time, suggesting that the biosynthesis of polar metabolites of Calendula officinalis is not affected by changes in soil composition. Therefore, this plant could represent a source for phytomedicines with a constant content of polar metabolites.

  6. Circularly polarized antennas

    CERN Document Server

    Gao, Steven; Zhu, Fuguo

    2013-01-01

    This book presents a comprehensive insight into the design techniques for different types of CP antenna elements and arrays In this book, the authors address a broad range of topics on circularly polarized (CP) antennas. Firstly, it introduces to the reader basic principles, design techniques and characteristics of various types of CP antennas, such as CP patch antennas, CP helix antennas, quadrifilar helix antennas (QHA), printed quadrifilar helix antennas (PQHA), spiral antenna, CP slot antennas, CP dielectric resonator antennas, loop antennas, crossed dipoles, monopoles and CP horns. Adva

  7. Plasma polarization spectroscopy

    CERN Document Server

    Iwamae, Atsushi

    2008-01-01

    Plasma Polarization Spectroscopy (PPS) is now becoming a standard diagnostic technique for working with laboratory plasmas. This new area needs a comprehensive framework, both experimental and theoretical. This book reviews the historical development of PPS, develops a general theoretical formulation to deal with this phenomenon, along with an overview of relevant cross sections, and reports on laboratory experiments so far performed. It also includes various facets that are interesting from this standpoint, e.g. X-ray lasers and effects of microwave irradiation. It also offers a timely discussion of instrumentation that is quite important in a practical PPS experiment.

  8. System for measuring the proton polarization in a polarized target

    International Nuclear Information System (INIS)

    Karnaukhov, I.M.; Lukhanin, A.A.; Telegin, Yu.N.; Trotsenko, V.I.; Chechetenko, V.F.

    1984-01-01

    The system for measuring the proton polarization in a polarized target representing the high-sensitivity nuclear magnetic resonance (NMR) is described Q-meter with series connection and a circuit for measuring system resonance characteristic is used for NMR-absorption signal recording. Measuring coil is produced of a strip conductor in order to obtain uniform system sensitivity to polarization state in all target volume and improve signal-to-noise ratio. Polarization measuring system operates ion-line with the M-6000 computer. The total measuring error for the value of free proton polarization in target taking into account the error caused by local depolarization of working substance under irradiation by high-intense photon beam is <= 6%. Long-term application of the described system for measuring the proton polarization in the LUEh-20000 accelerator target used in the pion photoproduction experiments has demonstrated its high reliability

  9. Preliminary studies of the biosynthesis of Austin

    International Nuclear Information System (INIS)

    Wicnienski, N.A.

    1979-01-01

    Aspergillus ustus is one of the most prevalent fungi in the soil. There are now two reports of the occurrence of toxin-producing strains of this fungus on stored foodstuffs. In addition, strains of A. ustus have been isolated along with Penicillium species from samples of South African cheeses. All A. ustus isolates tested were judged to be highly toxic to ducklings when grown on maize meal, however, the toxins involved were not isolated. Austin is the trivial name of one of the toxins made by the fungus found on stored food. Preliminary work to studying the biosynthesis of this compound using 13 C-labeled sodium acetate is reported here. The feasibility of the biosynthetic study was determined by feeding [1- 14 C]-sodium acetate to A. ustus cultures. The assignments made in the 13 C-nmr spectrum of Austin are shown. The lowest dilution factor obtained in [1- 14 C]-sodium acetate feeding experiments was 14. This dilution factor is sufficiently low to allow a successful feeding of [1,2- 13 C 2 ]-sodium acetate. A new metabolite of A. ustus, deacetylaustin, was isolated and identified. An alkaloid of unknown structure was also isolated from the fungus

  10. Biosynthesis of secondary metabolites in sugarcane

    Directory of Open Access Journals (Sweden)

    S.C. França

    2001-12-01

    Full Text Available A set of genes related to secondary metabolism was extracted from the sugarcane expressed sequence tag (SUCEST database and was used to investigate both the gene expression pattern of key enzymes regulating the main biosynthetic secondary metabolism pathways and the major classes of metabolites involved in the response of sugarcane to environmental and developmental cues. The SUCEST database was constructed with tissues in different physiological conditions which had been collected under varied situation of environmental stress. This database allows researchers to identify and characterize the expressed genes of a wide range of putative enzymes able to catalyze steps in the phenylpropanoid, isoprenoid and other pathways of the special metabolic mechanisms involved in the response of sugarcane to environmental changes. Our results show that sugarcane cDNAs encoded putative ultra-violet induced sesquiterpene cyclases (SC; chalcone synthase (CHS, the first enzyme in the pathway branch for flavonoid biosynthesis; isoflavone synthase (IFS, involved in plant defense and root nodulation; isoflavone reductase (IFR, a key enzyme in phenylpropanoid phytoalexin biosynthesis; and caffeic acid-O-methyltransferase, a key enzyme in the biosynthesis of lignin cell wall precursors. High levels of CHS transcripts from plantlets infected with Herbaspirillum rubri or Gluconacetobacter diazotroficans suggests that agents of biotic stress can elicit flavonoid biosynthesis in sugarcane. From this data we have predicted the profile of isoprenoid and phenylpropanoid metabolism in sugarcane and pointed the branches of secondary metabolism activated during tissue-specific stages of development and the adaptive response of sugarcane to agents of biotic and abiotic stress, although our assignment of enzyme function should be confirmed by careful biochemical and genetic supporting evidence.Este trabalho foi realizado com os objetivos de gerar uma coleção de genes

  11. Tyrosine biosynthesis, metabolism, and catabolism in plants.

    Science.gov (United States)

    Schenck, Craig A; Maeda, Hiroshi A

    2018-05-01

    L-Tyrosine (Tyr) is an aromatic amino acid (AAA) required for protein synthesis in all organisms, but synthesized de novo only in plants and microorganisms. In plants, Tyr also serves as a precursor of numerous specialized metabolites that have diverse physiological roles as electron carriers, antioxidants, attractants, and defense compounds. Some of these Tyr-derived plant natural products are also used in human medicine and nutrition (e.g. morphine and vitamin E). While the Tyr biosynthesis and catabolic pathways have been extensively studied in microbes and animals, respectively, those of plants have received much less attention until recently. Accumulating evidence suggest that the Tyr biosynthetic pathways differ between microbes and plants and even within the plant kingdom, likely to support the production of lineage-specific plant specialized metabolites derived from Tyr. The interspecies variations of plant Tyr pathway enzymes can now be used to enhance the production of Tyr and Tyr-derived compounds in plants and other synthetic biology platforms. Copyright © 2018 Elsevier Ltd. All rights reserved.

  12. Engineering bacteria for enhanced polyhydroxyalkanoates (PHA biosynthesis

    Directory of Open Access Journals (Sweden)

    Guo-Qiang Chen

    2017-09-01

    Full Text Available Polyhydroxyalkanoates (PHA have been produced by some bacteria as bioplastics for many years. Yet their commercialization is still on the way. A few issues are related to the difficulty of PHA commercialization: namely, high cost and instabilities on molecular weights (Mw and structures, thus instability on thermo-mechanical properties. The high cost is the result of complicated bioprocessing associated with sterilization, low conversion of carbon substrates to PHA products, and slow growth of microorganisms as well as difficulty of downstream separation. Future engineering on PHA producing microorganisms should be focused on contamination resistant bacteria especially extremophiles, developments of engineering approaches for the extremophiles, increase on carbon substrates to PHA conversion and controlling Mw of PHA. The concept proof studies could still be conducted on E. coli or Pseudomonas spp. that are easily used for molecular manipulations. In this review, we will use E. coli and halophiles as examples to show how to engineer bacteria for enhanced PHA biosynthesis and for increasing PHA competitiveness.

  13. Engineering bacteria for enhanced polyhydroxyalkanoates (PHA) biosynthesis.

    Science.gov (United States)

    Chen, Guo-Qiang; Jiang, Xiao-Ran

    2017-09-01

    Polyhydroxyalkanoates (PHA) have been produced by some bacteria as bioplastics for many years. Yet their commercialization is still on the way. A few issues are related to the difficulty of PHA commercialization: namely, high cost and instabilities on molecular weights (Mw) and structures, thus instability on thermo-mechanical properties. The high cost is the result of complicated bioprocessing associated with sterilization, low conversion of carbon substrates to PHA products, and slow growth of microorganisms as well as difficulty of downstream separation. Future engineering on PHA producing microorganisms should be focused on contamination resistant bacteria especially extremophiles, developments of engineering approaches for the extremophiles, increase on carbon substrates to PHA conversion and controlling Mw of PHA. The concept proof studies could still be conducted on E. coli or Pseudomonas spp. that are easily used for molecular manipulations. In this review, we will use E. coli and halophiles as examples to show how to engineer bacteria for enhanced PHA biosynthesis and for increasing PHA competitiveness.

  14. Biosynthesis of myristic acid in luminescent bacteria

    International Nuclear Information System (INIS)

    Byers, D.M.

    1987-01-01

    In vivo pulse-label studies have demonstrated that luminescent bacteria can provide myritic acid (14:0) required for the synthesis of the luciferase substrate myristyl aldehyde. Luminescent wild type Vibrio harveyi incubated with [ 14 C] acetate in a nutrient-depleted medium accumulated substantial tree [ 14 C]fatty acid (up to 20% of the total lipid label). Radio-gas chromatography revealed that > 75% of the labeled fatty acid is 14:0. No free fatty acid was detected in wild type cells labeled prior to the development of bioluminescence in the exponential growth phase, or in a dark mutant of V. harveyi (mutant M17) that requires exogenous 14:0 for light emission. The preferential accumulation of 14:0 was not observed when wild type cells were labeled with [ 14 C]acetate in regular growth medium. Moreover, all V. harveyi strains exhibited similar fatty acid mass compositions regardless of the state of bioluminescence. Since earlier work has shown that a luminescence-related acyltransferase (defective in the M17 mutant) can catalyze the deacylation of fatty acyl-acyl carrier protein in vitro, the present results are consistent with a model in which this enzyme diverts 14:0 to the luminescence system during fatty acid biosynthesis. Under normal conditions, the supply of 14:0 by this pathway is tightly regulated such that bioluminescence development does not significantly alter the total fatty acid composition

  15. Control of triacylglycerol biosynthesis in plants

    Energy Technology Data Exchange (ETDEWEB)

    1993-01-31

    Seeds of most species of the Umbelliferae (Apiaciae), Araliaceae, and Garryaceae families are characterized by their high content of the unusual C[sub 18] monounsaturated fatty acid petroselinic acid (18:l[Delta][sup 6cis]). Prior to a recent report of this lab, little was known of the biosynthetic origin of the cis[Delta][sup 6] double bond of petroselinic acid. Such knowledge may be of both biochemical and biotechnological significance. Because petroselinic acid is potentially the product of a novel desaturase, information regarding its synthesis may contribute to an understanding of fatty acid desaturation mechanisms in plants. Through chemical cleavage at its double bond, petroselinic acid can be used as a precursor of lauric acid (12:0), a component of detergents and surfactants, and adipic acid (6:0 dicarboxylic), the monomeric component of nylon 6,6. Therefore, the development of an agronomic source of an oil rich in petroselinic acid is of biotechnological interest. As such, studies of petroselinic acid biosynthesis may provide basic information required for any attempt to genetically engineer the production and accumulation of this fatty acid in an existing oilseed.

  16. A Biotin Biosynthesis Gene Restricted to Helicobacter

    Science.gov (United States)

    Bi, Hongkai; Zhu, Lei; Jia, Jia; Cronan, John E.

    2016-01-01

    In most bacteria the last step in synthesis of the pimelate moiety of biotin is cleavage of the ester bond of pimeloyl-acyl carrier protein (ACP) methyl ester. The paradigm cleavage enzyme is Escherichia coli BioH which together with the BioC methyltransferase allows synthesis of the pimelate moiety by a modified fatty acid biosynthetic pathway. Analyses of the extant bacterial genomes showed that bioH is absent from many bioC-containing bacteria and is replaced by other genes. Helicobacter pylori lacks a gene encoding a homologue of the known pimeloyl-ACP methyl ester cleavage enzymes suggesting that it encodes a novel enzyme that cleaves this intermediate. We isolated the H. pylori gene encoding this enzyme, bioV, by complementation of an E. coli bioH deletion strain. Purified BioV cleaved the physiological substrate, pimeloyl-ACP methyl ester to pimeloyl-ACP by use of a catalytic triad, each member of which was essential for activity. The role of BioV in biotin biosynthesis was demonstrated using a reconstituted in vitro desthiobiotin synthesis system. BioV homologues seem the sole pimeloyl-ACP methyl ester esterase present in the Helicobacter species and their occurrence only in H. pylori and close relatives provide a target for development of drugs to specifically treat Helicobacter infections. PMID:26868423

  17. The regulation and biosynthesis of antimycins

    Directory of Open Access Journals (Sweden)

    Ryan F. Seipke

    2013-11-01

    Full Text Available Antimycins (>40 members were discovered nearly 65 years ago but the discovery of the gene cluster encoding antimycin biosynthesis in 2011 has facilitated rapid progress in understanding the unusual biosynthetic pathway. Antimycin A is widely used as a piscicide in the catfish farming industry and also has potent killing activity against insects, nematodes and fungi. The mode of action of antimycins is to inhibit cytochrome c reductase in the electron transport chain and halt respiration. However, more recently, antimycin A has attracted attention as a potent and selective inhibitor of the mitochondrial anti-apoptotic proteins Bcl-2 and Bcl-xL. Remarkably, this inhibition is independent of the main mode of action of antimycins such that an artificial derivative named 2-methoxyantimycin A inhibits Bcl-xL but does not inhibit respiration. The Bcl-2/Bcl-xL family of proteins are over-produced in cancer cells that are resistant to apoptosis-inducing chemotherapy agents, so antimycins have great potential as anticancer drugs used in combination with existing chemotherapeutics. Here we review what is known about antimycins, the regulation of the ant gene cluster and the unusual biosynthetic pathway.

  18. Estrogen biosynthesis in human uterine adenomyosis

    International Nuclear Information System (INIS)

    Urabe, Mamoru; Yamamoto, Takara; Kitawaki, Jo; Honjo, Hideo; Okada, Hiroji

    1989-01-01

    Estrogen biosynthesis (aromatiase activity) was investigated in human adenomyosis tissue and compared with that of the normal myometrium, endometrium, and endometrical cancer tissues. Homogenates were incubated with [1,2,6,7- 3 H]androstenedione and NADPH at 37 deg. C for 1 h. After stopping the enzymatic reaction with ethyl acetate, [4- 14 C]estrone and [4- 14 C]estradiol-17β were added to the incubated sample. Estrone and estradiol were purified and identified by Bio-Rad AG1-X2 column chromatography, thin-layer chromatography and co-crystallization. Estrogen formed in the incubated sample was calculated from the 3 H/ 14 C ratio of the final crystal. The value for estrone formed from androstenedione was 52-132 fmol . h -1. g -1 wet weight. Aromatase activity in the adenomyosis tissues was higher than that in normal endometrial or myometrial tissues, but lower than that found in myometrial or endometrial tumour tissue. Furthermore, we investigated the effect of danazol, progresterone, and medroxyprogesterone acetate on adenomyosis cells in primary cultures. Aromatase activity in adenomyosis was blocked by danazol, but stimulated by progesterone and MPA. These results indicate that aromatase activity in adenomyosis may contribute to the growth of the ectopic endometrial tissue which occurs in this disease. (author)

  19. Glycoprotein biosynthesis by human normal platelets

    International Nuclear Information System (INIS)

    Rodriguez, P.; Bello, O.; Apitz-Castro, R.

    1987-01-01

    Incorporation of radioactive Man, Gal, Fuc, Glc-N, and NANA into washed human normal platelets and endogenous glycoproteins has been found. Both parameters were time dependent. Analysis of hydrolyzed labeled glycoproteins by paper chromatography revealed that the radioactive monosaccharide incubated with the platelets had not been converted into other sugars. Acid hydrolysis demonstrates the presence of a glycosidic linkage. All the effort directed to the demonstration of the existence of a lipid-sugar intermediate in intact human platelets yielded negative results for Man and Glc-N used as precursors. The incorporation of these sugars into glycoproteins is insensitive to bacitracin, suggesting no involvement of lipid-linked saccharides in the synthesis of glycoproteins in human blood platelets. The absence of inhibition of the glycosylation process in the presence of cycloheximide suggests that the sugars are added to proteins present in the intact platelets. These results support the contention that glycoprotein biosynthesis in human blood platelets observed under our experimental conditions is effected through direct sugar nucleotide glycosylation

  20. Biosynthesis and metabolism of steroids in molluscs.

    Science.gov (United States)

    Fernandes, Denise; Loi, Barbara; Porte, Cinta

    2011-11-01

    Molluscs are the second most diverse animal group, they are ecologically important and they are considered excellent indicators of ecosystem health. Some species have been widely used in pollution biomonitoring programs; however, their endocrinology is still poorly known. Despite some studies reporting the presence of (vertebrate-type) steroids in molluscs, information regarding enzymatic pathways involved in steroid synthesis and further catabolism of those steroids is still fragmentary. Regarding steroidogenesis, a number of excellent studies were performed in the 70s using different radio-labelled steroid precursors and detecting the formation of different metabolites. But, since then a long gap of research exist until the late 90s when the 'endocrine disruption' issue raised the need of a better knowledge of mollusc (and invertebrate) endocrinology in order to assess alterations caused by pollutants. Here we summarize past and recent studies dealing with steroid biosynthesis and metabolism in different mollusc species. Most of these studies suggest the involvement of steroids in mollusc reproduction. However, the knowledge is still fragmentary and many questions remain to be answered. Copyright © 2010 Elsevier Ltd. All rights reserved.

  1. Transcriptional analysis of apple fruit proanthocyanidin biosynthesis

    Science.gov (United States)

    Henry-Kirk, Rebecca A.

    2012-01-01

    Proanthocyanidins (PAs) are products of the flavonoid pathway, which also leads to the production of anthocyanins and flavonols. Many flavonoids have antioxidant properties and may have beneficial effects for human health. PAs are found in the seeds and fruits of many plants. In apple fruit (Malus × domestica Borkh.), the flavonoid biosynthetic pathway is most active in the skin, with the flavan-3-ols, catechin, and epicatechin acting as the initiating units for the synthesis of PA polymers. This study examined the genes involved in the production of PAs in three apple cultivars: two heritage apple cultivars, Hetlina and Devonshire Quarrenden, and a commercial cultivar, Royal Gala. HPLC analysis shows that tree-ripe fruit from Hetlina and Devonshire Quarrenden had a higher phenolic content than Royal Gala. Epicatechin and catechin biosynthesis is under the control of the biosynthetic enzymes anthocyanidin reductase (ANR) and leucoanthocyanidin reductase (LAR1), respectively. Counter-intuitively, real-time quantitative PCR analysis showed that the expression levels of Royal Gala LAR1 and ANR were significantly higher than those of both Devonshire Quarrenden and Hetlina. This suggests that a compensatory feedback mechanism may be active, whereby low concentrations of PAs may induce higher expression of gene transcripts. Further investigation is required into the regulation of these key enzymes in apple. Abbreviations:ANOVAanalysis of varianceANRanthocyanidin reductaseDADdiode array detectorDAFBdays after full bloomDFRdihydroflavonol reductaseLARleucoanthocyanidin reductaseLC-MSliquid chromatography/mass spectrometryPAproanthocyanidinqPCRreal-time quantitative PCR PMID:22859681

  2. Explorations into the biosynthesis of bioscorine

    Energy Technology Data Exchange (ETDEWEB)

    Michelson, R.H.

    1988-01-01

    The biosynthesis of dioscorine in Dioscorea hispida has been studied by the feeding of putative precursors labelled at specific positions with {sup 2}H, {sup 3}H, and {sup 14}C. Administration of (3-{sup 14}C)3-hydroxy-3-methylglutaric acid to D. hispida by the wick method afforded dioscorine labelled preferentially at the C{sub 10} position implying that the biosynthetic pathway to the acetate-derived half of the dioscorine skeleton is going through this compound. Administration of ethyl (6-{sup 14}C)orsellinate to D. hispida by the wick method failed to give an appreciable incorporation into dioscroine thereby disproving an alternative mechanism describing the formation of the acetate-derived half of the dioscorine skeleton. Two attempts to simulate the alternative mechanism by oxidatively cleaving ethyl orsellinate also failed, further disfavoring this mechanism. Administration of (2,3){sup 13}C{sub 2}, {sup 14}C{sub 2}succinic acid, (3-{sup 14}C)aspartic acid and (7a-{sup 14}C)tryptophan by the leaf painting method gave very low incorporations into dioscorine making determination of the source of the nicotinic acid half of the dioscorine skeleton inconclusive. Administration of (6-{sup 2}H, {sup 3}H)nicotinic acid to D. hispida by the wick method afforded dioscorine exhibiting complete retention of {sup 3}H thereby disfavoring a mechanism involving a 3,6-dihydropyridine intermediate in the formation of the dioscorine skeleton.

  3. Polar drive on OMEGA

    Directory of Open Access Journals (Sweden)

    Radha P.B.

    2013-11-01

    Full Text Available High-convergence polar-drive experiments are being conducted on OMEGA [T. R. Boehly et al., Opt. Commum. 133, 495 (1997] using triple-picket laser pulses. The goal of OMEGA experiments is to validate modeling of oblique laser deposition, heat conduction in the presence of nonradial thermal gradients in the corona, and implosion energetics in the presence of laser–plasma interactions such as crossed-beam energy transfer. Simulated shock velocities near the equator, where the beams are obliquely incident, are within 5% of experimentally inferred values in warm plastic shells, well within the required accuracy for ignition. High, near-one-dimensional areal density is obtained in warm-plastic-shell implosions. Simulated backlit images of the compressing core are in good agreement with measured images. Outstanding questions that will be addressed in the future relate to the role of cross-beam transfer in polar drive irradiation and increasing the energy coupled into the target by decreasing beam obliquity.

  4. Enhanced glutathione content allows the in vivo synthesis of fluorescent CdTe nanoparticles by Escherichia coli.

    Directory of Open Access Journals (Sweden)

    Juan P Monrás

    Full Text Available The vast application of fluorescent semiconductor nanoparticles (NPs or quantum dots (QDs has prompted the development of new, cheap and safer methods that allow generating QDs with improved biocompatibility. In this context, green or biological QDs production represents a still unexplored area. This work reports the intracellular CdTe QDs biosynthesis in bacteria. Escherichia coli overexpressing the gshA gene, involved in glutathione (GSH biosynthesis, was used to produce CdTe QDs. Cells exhibited higher reduced thiols, GSH and Cd/Te contents that allow generating fluorescent intracellular NP-like structures when exposed to CdCl(2 and K(2TeO(3. Fluorescence microscopy revealed that QDs-producing cells accumulate defined structures of various colors, suggesting the production of differently-sized NPs. Purified fluorescent NPs exhibited structural and spectroscopic properties characteristic of CdTe QDs, as size and absorption/emission spectra. Elemental analysis confirmed that biosynthesized QDs were formed by Cd and Te with Cd/Te ratios expected for CdTe QDs. Finally, fluorescent properties of QDs-producing cells, such as color and intensity, were improved by temperature control and the use of reducing buffers.

  5. Polarized proton collider at RHIC

    Energy Technology Data Exchange (ETDEWEB)

    Alekseev, I.; Allgower, C.; Bai, M.; Batygin, Y.; Bozano, L.; Brown, K.; Bunce, G.; Cameron, P.; Courant, E.; Erin, S.; Escallier, J.; Fischer, W.; Gupta, R.; Hatanaka, K.; Huang, H.; Imai, K.; Ishihara, M.; Jain, A.; Lehrach, A.; Kanavets, V.; Katayama, T.; Kawaguchi, T.; Kelly, E.; Kurita, K.; Lee, S.Y.; Luccio, A.; MacKay, W.W. E-mail: mackay@bnl.govhttp://www.rhichome.bnl.gov/People/waldowaldo@bnl.gov; Mahler, G.; Makdisi, Y.; Mariam, F.; McGahern, W.; Morgan, G.; Muratore, J.; Okamura, M.; Peggs, S.; Pilat, F.; Ptitsin, V.; Ratner, L.; Roser, T.; Saito, N.; Satoh, H.; Shatunov, Y.; Spinka, H.; Syphers, M.; Tepikian, S.; Tominaka, T.; Tsoupas, N.; Underwood, D.; Vasiliev, A.; Wanderer, P.; Willen, E.; Wu, H.; Yokosawa, A.; Zelenski, A.N

    2003-03-01

    In addition to heavy ion collisions (RHIC Design Manual, Brookhaven National Laboratory), RHIC will also collide intense beams of polarized protons (I. Alekseev, et al., Design Manual Polarized Proton Collider at RHIC, Brookhaven National Laboratory, 1998, reaching transverse energies where the protons scatter as beams of polarized quarks and gluons. The study of high energy polarized protons beams has been a long term part of the program at BNL with the development of polarized beams in the Booster and AGS rings for fixed target experiments. We have extended this capability to the RHIC machine. In this paper we describe the design and methods for achieving collisions of both longitudinal and transverse polarized protons in RHIC at energies up to {radical}s=500 GeV.

  6. Spin exchange in polarized deuterium

    International Nuclear Information System (INIS)

    Przewoski, B. von; Meyer, H.O.; Balewski, J.; Doskow, J.; Ibald, R.; Pollock, R.E.; Rinckel, T.; Wellinghausen, A.; Whitaker, T.J.; Daehnick, W.W.; Haeberli, W.; Schwartz, B.; Wise, T.; Lorentz, B.; Rathmann, F.; Pancella, P.V.; Saha, Swapan K.; Thoerngren-Engblom, P.

    2003-01-01

    We have measured the vector and tensor polarization of an atomic deuterium target as a function of the target density. The polarized deuterium was produced in an atomic beam source and injected into a storage cell. For this experiment, the atomic beam source was operated without rf transitions, in order to avoid complications from the unknown efficiency of these transitions. In this mode, the atomic beam is vector and tensor polarized and both polarizations can be measured simultaneously. We used a 1.2-cm-diam and 27-cm-long storage cell, which yielded an average target density between 3 and 9x10 11 at/cm 3 . We find that the tensor polarization decreases with increasing target density while the vector polarization remains constant. The data are in quantitative agreement with the calculated effect of spin exchange between deuterium atoms at low field

  7. Resonance Polarization and Phase-Mismatched CARS of Pheophytin b Excited in the Qy Band

    NARCIS (Netherlands)

    de Boeij, W.P.; Lucassen, G.W.; Lucassen, Gerald; Otto, Cornelis; Greve, Jan

    1993-01-01

    Resonance polarization and phase-mismatched coherent anti-Stokes Raman scattering (CARS) measurements were performed on pheophytin b dissolved in acetone excited in the Qy absorption band, where strong broad fluorescence makes spontaneous Raman spectroscopy impossible. The phase-mismatching

  8. Imaging of polarity during zygotic and somatic embryogenesis of carrot (Daucus carota L.)

    NARCIS (Netherlands)

    Timmers, A.C.J.

    1993-01-01

    In this thesis a study of the regulation of coordinated growth and the development of polarity during embryogenesis of carrot, Daucus carota L., is described. To this end, several microscopical techniques were used, such as light microscopy, fluorescence microscopy,

  9. Plasmon-induced modulation of the emission spectra of the fluorescent molecules near gold nanorods.

    Science.gov (United States)

    Zhao, Lei; Ming, Tian; Chen, Huanjun; Liang, Yao; Wang, Jianfang

    2011-09-01

    Both the excitation and emission processes of a fluorescent molecule positioned near a noble metal nanocrystal can interact strongly with the localized surface plasmon resonance of the metal nanocrystal. While the effects of this plasmon-fluorophore interaction on the intensity, polarization, and direction of the fluorescence emission have been intensively investigated, the plasmonic effect on the emission spectrum has barely been explored. We show, on the single-particle level, that the localized surface plasmon resonance of Au nanorods can strongly alter the spectral profile of the emission from adjacent fluorescent molecules. The fluorescent molecules are embedded in a mesostructured silica shell that is uniformly coated on each Au nanorod. The longitudinal plasmon resonance wavelengths of the nanorods are deliberately shifted away from the intrinsic fluorescence emission peak wavelength by synthetically tuning the nanorod aspect ratio. The resultant emission spectra of the fluorescent molecules are found to be remarkably modulated. Besides the intrinsic fluorescence peak, a plasmon-induced new peak emerges at the plasmon resonance wavelength. The intensity of this plasmon-induced fluorescence peak increases as the size of the Au nanorod is increased. This spectral modulation can be understood by depicting the decay process of the fluorophore with multiple vibrational energy levels. The plasmon with a specific resonance energy will enhance the transition rate between the energy levels that have the transition energy approximately equal to the plasmon energy. This plasmon-enhanced transition rate results in a modulated spectral profile of the fluorescence emission.

  10. Linear polarization of BY Draconis

    International Nuclear Information System (INIS)

    Koch, R.H.; Pfeiffer, R.J.

    1976-01-01

    Linear polarization measurements are reported in four bandpasses for the flare star BY Dra. The red polarization is intrinsically variable at a confidence level greater than 99 percent. On a time scale of many months, the variability is not phase-locked to either a rotational or a Keplerian ephemeris. The observations of the three other bandpasses are useful principally to indicate a polarization spectrum rising toward shorter wavelengths

  11. Polarity in Mammalian Epithelial Morphogenesis

    OpenAIRE

    Roignot, Julie; Peng, Xiao; Mostov, Keith

    2013-01-01

    Cell polarity is fundamental for the architecture and function of epithelial tissues. Epithelial polarization requires the intervention of several fundamental cell processes, whose integration in space and time is only starting to be elucidated. To understand what governs the building of epithelial tissues during development, it is essential to consider the polarization process in the context of the whole tissue. To this end, the development of three-dimensional organotypic cell culture model...

  12. New insight in the template decomposition process of large zeolite ZSM-5 crystals: an in situ UV-Vis/fluorescence micro-spectroscopy study

    NARCIS (Netherlands)

    Karwacki, L.; Weckhuysen, B.M.

    2011-01-01

    A combination of in situ UV-Vis and confocal fluorescence micro-spectroscopy was used to study the template decomposition process in large zeolite ZSM-5 crystals. Correlation of polarized light dependent UV-Vis absorption spectra with confocal fluorescence emission spectra in the 400–750 nm region

  13. Detection of bacterial infection of agave plants by laser-induced fluorescence

    Science.gov (United States)

    Cervantes-Martinez, Jesus; Flores-Hernandez, Ricardo; Rodriguez-Garay, Benjamin; Santacruz-Ruvalcaba, Fernando

    2002-05-01

    Greenhouse-grown plants of Agave tequilana Weber var. azul were inoculated with Erwinia carotovora, the causal agent of stem soft rot. We investigated the laser-induced fluorescence (LIF) of agave plants to determine whether LIF can be used as a noninvasive sensing tool for pathological studies. The LIF technique was also investigated as a means of detecting the effect of the polyamine biosynthesis inhibitor beta-hydroxyethylhydrazine as a bactericide against the pathogenic bacterium Erwinia carotovora. A He-Ne laser at 632.8 nm was used as the excitation source, and in vivo fluorescence emission spectra were recorded in the 660-790-range. Fluorescence maxima were at 690 and 740 nm. The infected plants that were untreated with the bactericide showed a definite increase in fluorescence intensity at both maxima within the first three days after infection. Beginning on the fifth day, a steady decrease in fluorescence intensity was observed, with a greater effect at 740 than at 690 nm. After 30 days there was no fluorescence. The infected plants that had been treated with the bactericide showed no significant change in fluorescence compared with that of the uninfected plants. The ratio of fluorescence intensities was determined to be F 690 nm/F 740 nm for all treatments. These studies indicate that LIF measurements of agave plants may be used for the early detection of certain types of disease and for determining the effect of a bactericide on bacteria. The results also showed that fluorescence intensity ratios can be used as a reliable indicator of the progress of disease.

  14. A polarized alkali ion source

    International Nuclear Information System (INIS)

    Boettger, R.; Tungate, G.; Bauer, B.; Egelhof, P.; Moebius, K.H.; Steffens, E.

    1978-01-01

    The beam foil technique has been applied to detect nuclear vector polarization of a 10 keV 23 Na + beam. The result was about 70% of the atomic beam polarization thus limiting the depolarization by the surface ionizer to at most 30%. In a Coulomb excitation experiment with a tensor polarized 42 MeV 23 Na 7+ beam an effect of 0.011 +- 0.003 was measured yielding a value of t 20 approx. 0.04 for the beam polarization. The depolarization during the acceleration process can be estimated to be about 0.8. (orig.) [de

  15. The SLAC polarized electron source

    International Nuclear Information System (INIS)

    Tang, H.; Alley, R.; Frisch, J.

    1995-06-01

    The SLAC polarized electron source employs a photocathode DC high voltage gun with a loadlock and a YAG pumped Ti:sapphire laser system for colliding beam experiments or a flash lamp pumped Ti:sapphire laser for fixed target experiments. It uses a thin, strained GaAs(100) photocathode, and is capable of producing a pulsed beam with a polarization of ≥80% and a peak current exceeding 10 A. Its operating efficiency has reached 99%. The physics and technology of producing high polarization electron beams from a GaAs photocathode will be reviewed. The prospects of realizing a polarized electron source for future linear colliders will also be discussed

  16. Fluorescent Silicon Clusters and Nanoparticles

    OpenAIRE

    von Haeften, Klaus

    2017-01-01

    The fluorescence of silicon clusters is reviewed. Atomic clusters of silicon have been at the focus of research for several decades because of the relevance of size effects for material properties, the importance of silicon in electronics and the potential applications in bio-medicine. To date numerous examples of nanostructured forms of fluorescent silicon have been reported. This article introduces the principles and underlying concepts relevant for fluorescence of nanostructured silicon su...

  17. Development of a fluorescent cryocooler

    International Nuclear Information System (INIS)

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

    1995-01-01

    Recent work at Los Alamos National Laboratory has demonstrated the physical principles for a new type of solid-state cryocooler based on anti-Stokes fluorescence. Design studies indicate that a vibration-free, low-mass ''fluorescent cryocooler'' could operate for years with efficiencies and cooling powers comparable to current commercial systems. This paper presents concepts for a fluorescent cryocooler, design considerations and expected performance

  18. New insights on the fluorescent emission spectra of Prodan and Laurdan.

    Science.gov (United States)

    Vequi-Suplicy, Cíntia C; Coutinho, Kaline; Lamy, M Teresa

    2015-05-01

    Prodan and Laurdan are fluorescent probes largely used in biological systems. They were synthetized to be sensitive to the environment polarity, and their fluorescent emission spectrum shifts around 120 nm, from cyclohexane to water. Although accepted that their emission spectrum is composed by two emission bands, the origin of these two bands is still a matter of discussion. Here we analyze the fluorescent spectra of Prodan and Laurdan in solvents of different polarities, both by decomposing the spectrum into two Gaussian bands and by computing the Decay Associated Spectra (DAS), the latter with time resolved fluorescence. Our data show that the intensity of the lower energy emission band of Prodan and Laurdan (attributed, in the literature, to the decay of a solvent relaxed state) is higher in cyclohexane than in water, showing a decrease as the polarity of the medium increases. Moreover, in all solvents studied here, the balance between the two emission bands is not dependent on the temperature, strongly suggesting two independent excited states. Both bands were found to display a red shift as the medium polarity increases. We propose here a new interpretation for the two emission bands of Prodan and Laurdan in homogeneous solvents: they would be related to the emission of two independent states, and not to a pair of non-relaxed and solvent relaxed states.

  19. Time-resolved fluorescence analysis of the mobile flavin cofactor in ...

    Indian Academy of Sciences (India)

    TECS

    Abstract. Conformational heterogeneity of the FAD cofactor in p-hydroxybenzoate hydroxylase. (PHBH) was investigated with time-resolved polarized flavin fluorescence. For binary enzyme/substrate. (analogue) complexes of wild-type PHBH and Tyr222 mutants, crystallographic studies have revealed two distinct flavin ...

  20. Dithiolopyrrolone Natural Products: Isolation, Synthesis and Biosynthesis

    Science.gov (United States)

    Qin, Zhiwei; Huang, Sheng; Yu, Yi; Deng, Hai

    2013-01-01

    Dithiolopyrrolones are a class of antibiotics that possess the unique pyrrolinonodithiole (4H-[1,2] dithiolo [4,3-b] pyrrol-5-one) skeleton linked to two variable acyl groups. To date, there are approximately 30 naturally occurring dithiolopyrrolone compounds, including holomycin, thiolutin, and aureothricin, and more recently thiomarinols, a unique class of hybrid marine bacterial natural products containing a dithiolopyrrolone framework linked by an amide bridge with an 8-hydroxyoctanoyl chain linked to a monic acid. Generally, dithiolopyrrolone antibiotics have broad-spectrum antibacterial activity against various microorganisms, including Gram-positive and Gram-negative bacteria, and even parasites. Holomycin appeared to be active against rifamycin-resistant bacteria and also inhibit the growth of the clinical pathogen methicillin-resistant Staphylococcus aureus N315. Its mode of action is believed to inhibit RNA synthesis although the exact mechanism has yet to be established in vitro. A recent work demonstrated that the fish pathogen Yersinia ruckeri employs an RNA methyltransferase for self-resistance during the holomycin production. Moreover, some dithiolopyrrolone derivatives have demonstrated promising antitumor activities. The biosynthetic gene clusters of holomycin have recently been identified in S. clavuligerus and characterized biochemically and genetically. The biosynthetic gene cluster of thiomarinol was also identified from the marine bacterium Pseudoalteromonas sp. SANK 73390, which was uniquely encoded by two independent pathways for pseudomonic acid and pyrrothine in a novel plasmid. The aim of this review is to give an overview about the isolations, characterizations, synthesis, biosynthesis, bioactivities and mode of action of this unique family of dithiolopyrrolone natural products, focusing on the period from 1940s until now. PMID:24141227

  1. Biosynthesis of 2'-deoxycoformycin by Streptomyces antibioticus

    International Nuclear Information System (INIS)

    Hanvey, J.C.

    1986-01-01

    The biosynthesis of 2'-deoxycoformycin by Streptomyces antibioticus has been investigated. Previous studies indicated that a purine nycleoside is the precursor for ten of the eleven carbons of deoxycoformycin. It was proposed that carbon-7 of the seven-membered, 1,3-diazepine-ring of deoxycoformycin is not derived from the purine ring but by an insertion of a one-carbon unit between N-1 and C-6 of the purine ring. Carbon-1 of D-ribose has now been identified as the precursor for carbon 7 (and 1') of deoxycoformycin. Although the tetrahydrofolate/one-carbon pool contributes one carbon units to carbons-2 and 8 of the purine ring, which become carbons-5 and 2 of deoxycoformycin, it is not involved in the formation of carbon-7. The retention of the tritium on carbon-2 of [2,8- 3 H]-adenosine in deoxycoformycin indicates that guanosine is not the nucleoside precursor of deoxycoformycin. The failure to detect the incorporation of 18 O from [6- 18 O]-inosine in deoxycoformycin suggests that inosine is not the purine nucleoside precursor of deoxycoformycin. Therefore, it is proposed that adenosine and carbon-1 and d-ribose are the carbon-nitrogen precursors of deoxycoformycin. A mechanism for the insertion of carbon-1 of d-ribose into the pyrimidine portion of the purine ring has been proposed. Using cell-free extracts of S. antibioticus, 8-ketodeoxycoformycin and 8-ketocoformycin can be converted to deoxycoformycin and coformycin, respectively. The enzyme which reduces the 8-keto groups has been characterized and partially purified

  2. Benzobisoxazole cruciforms as fluorescent sensors.

    Science.gov (United States)

    Saeed, Musabbir A; Le, Ha T M; Miljanić, Ognjen Š

    2014-07-15

    related species. In self-assembled complexes with boronic acids, benzobisoxazole fluorophores switch their analyte preferences and become responsive to Lewis basic species: phenoxides, amines, ureas, and small organic and inorganic anions. These sensing complexes allow the decoupling of the sensor's two functions: a nonfluorescent boronic acid does the chemistry through the exchange of its labile B-O bonds for other nucleophiles, and it can be optimized for solubility and analyte specificity; the benzobisoxazole fluorophore senses the electronic changes on the boron and reports them to the operator through changes in its emission colors, allowing this sensing element to be kept constant across a broad range of analytes. We have recently expanded our studies to benzimidazole-based "half-cruciforms", which are L-shaped rigid fluorophores that maintain most of the spatial separation of FMOs observed in benzobisoxazole cruciforms. Unlike benzobisoxazoles, benzimidazoles are acidic on account of their polar N-H bonds, and this feature allows them to respond to a broader range of pH values than their benzobisoxazole counterparts. The deprotonated benzimidazolate anions maintain their fluorescence, which makes them promising candidates for incorporation into solid-state sensing materials known as zeolithic imidazolate frameworks.

  3. Polar Glycosylated and Lateral Non-Glycosylated Flagella from Aeromonas hydrophila Strain AH-1 (Serotype O11

    Directory of Open Access Journals (Sweden)

    Kelly M. Fulton

    2015-11-01

    Full Text Available Polar and but not lateral flagellin proteins from Aeromonas hydrophila strain AH-1 (serotype O11 were found to be glycosylated. Top-down mass spectrometry studies of purified polar flagellins suggested the presence of a 403 Da glycan of mass. Bottom-up mass spectrometry studies showed the polar flagellin peptides to be modified with 403 Da glycans in O-linkage. The MS fragmentation pattern of this putative glycan was similar to that of pseudaminic acid derivative. Mutants lacking the biosynthesis of pseudaminic acid (pseB and pseI homologues were unable to produce polar flagella but no changes were observed in lateral flagella by post-transcriptional regulation of the flagellin. Complementation was achieved by reintroduction of the wild-type pseB and pseI. We compared two pathogenic features (adhesion to eukaryotic cells and biofilm production between the wild-type strain and two kinds of mutants: mutants lacking polar flagella glycosylation and lacking the O11-antigen lipopolysaccharide (LPS but with unaltered polar flagella glycosylation. Results suggest that polar flagella glycosylation is extremely important for A. hydrophila AH-1 adhesion to Hep-2 cells and biofilm formation. In addition, we show the importance of the polar flagella glycosylation for immune stimulation of IL-8 production via toll-“like” receptor 5 (TLR5.

  4. Abnormal Ergosterol Biosynthesis Activates Transcriptional Responses to Antifungal Azoles.

    Science.gov (United States)

    Hu, Chengcheng; Zhou, Mi; Wang, Wenzhao; Sun, Xianyun; Yarden, Oded; Li, Shaojie

    2018-01-01

    Fungi transcriptionally upregulate expression of azole efflux pumps and ergosterol biosynthesis pathway genes when exposed to antifungal agents that target ergosterol biosynthesis. To date, these transcriptional responses have been shown to be dependent on the presence of the azoles and/or depletion of ergosterol. Using an inducible promoter to regulate Neurospora crassa erg11 , which encodes the major azole target, sterol 14α-demethylase, we were able to demonstrate that the CDR4 azole efflux pump can be transcriptionally activated by ergosterol biosynthesis inhibition even in the absence of azoles. By analyzing ergosterol deficient mutants, we demonstrate that the transcriptional responses by cdr4 and, unexpectedly, genes encoding ergosterol biosynthesis enzymes ( erg genes) that are responsive to azoles, are not dependent on ergosterol depletion. Nonetheless, deletion of erg2 , which encodes C-8 sterol isomerase, also induced expression of cdr4 . Deletion of erg2 also induced the expression of erg24 , the gene encoding C-14 sterol reductase, but not other tested erg genes which were responsive to erg11 inactivation. This indicates that inhibition of specific steps of ergosterol biosynthesis can result in different transcriptional responses, which is further supported by our results obtained using different ergosterol biosynthesis inhibitors. Together with the sterol profiles, these results suggest that the transcriptional responses by cdr4 and erg genes are associated with accumulation of specific sterol intermediate(s). This was further supported by the fact that when the erg2 mutant was treated with ketoconazole, upstream inhibition overrode the effects by downstream inhibition on ergosterol biosynthesis pathway. Even though cdr4 expression is associated with the accumulation of sterol intermediates, intra- and extracellular sterol analysis by HPLC-MS indicated that the transcriptional induction of cdr4 did not result in efflux of the accumulated intermediate

  5. Jasmonate-induced biosynthesis of andrographolide in Andrographis paniculata.

    Science.gov (United States)

    Sharma, Shiv Narayan; Jha, Zenu; Sinha, Rakesh Kumar; Geda, Arvind Kumar

    2015-02-01

    Andrographolide is a prominent secondary metabolite found in Andrographis paniculata that exhibits enormous pharmacological effects. In spite of immense value, the normal biosynthesis of andrographolide results in low amount of the metabolite. To induce the biosynthesis of andrographolide, we attempted elicitor-induced activation of andrographolide biosynthesis in cell cultures of A. paniculata. This was carried out by using methyl jasmonate (MeJA) as an elicitor. Among the various concentrations of MeJA tested at different time periods, 5 µM MeJA yielded 5.25 times more andrographolide content after 24 h of treatment. The accumulation of andrographolide was correlated with the expression level of known regulatory genes (hmgs, hmgr, dxs, dxr, isph and ggps) of mevalonic acid (MVA) and 2-C-methyl-d-erythritol-4-phosphate (MEP) pathways. These results established the involvement of MeJA in andrographolide biosynthesis by inducing the transcription of its biosynthetic pathways genes. The coordination of isph, ggps and hmgs expression highly influenced the andrographolide biosynthesis. © 2014 Scandinavian Plant Physiology Society.

  6. Biosynthesis and functions of sulfur modifications in tRNA

    Directory of Open Access Journals (Sweden)

    Naoki eShigi

    2014-04-01

    Full Text Available Sulfur is an essential element for a variety of cellular constituents in all living organisms. In tRNA molecules, there are many sulfur-containing nucleosides, such as the derivatives of 2‑thiouridine (s2U, 4-thiouridine (s4U, 2-thiocytidine (s2C, and 2-methylthioadenosine (ms2A. Earlier studies established the functions of these modifications for accurate and efficient translation, including proper recognition of the codons in mRNA or stabilization of tRNA structure. In many cases, the biosynthesis of these sulfur modifications starts with cysteine desulfurases, which catalyze the generation of persulfide (an activated form of sulfur from cysteine. Many sulfur-carrier proteins are responsible for delivering this activated sulfur to each biosynthesis pathway. Finally, specific modification enzymes activate target tRNAs and then incorporate sulfur atoms. Intriguingly, the biosynthesis of 2-thiouridine in all domains of life is functionally and evolutionarily related to the ubiquitin-like post-translational modification system of cellular proteins in eukaryotes. This review summarizes the recent characterization of the biosynthesis of sulfur modifications in tRNA and the novel roles of this modification in cellular functions in various model organisms, with a special emphasis on 2-thiouridine derivatives. Each biosynthesis pathway of sulfur-containing molecules is mutually modulated via sulfur trafficking, and 2-thiouridine and codon usage bias have been proposed to control the translation of specific genes.

  7. Polar Biomedical Research - An Assessment.

    Science.gov (United States)

    1982-10-01

    to grow more crops in subpolar Alaska. The severity of the polar conditions in Antarctica allow no practical method for providing volumes of plant food...for an expanded population. Any experiments in polar regions in food production involving geothermal heat, solar energy, hydroponics , or aquaculture

  8. Create a Polarized Light Show.

    Science.gov (United States)

    Conrad, William H.

    1992-01-01

    Presents a lesson that introduces students to polarized light using a problem-solving approach. After illustrating the concept using a slinky and poster board with a vertical slot, students solve the problem of creating a polarized light show using Polya's problem-solving methods. (MDH)

  9. Carbon nanotube fiber terahertz polarizer

    Energy Technology Data Exchange (ETDEWEB)

    Zubair, Ahmed [Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005 (United States); Tsentalovich, Dmitri E.; Young, Colin C. [Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005 (United States); Heimbeck, Martin S. [Charles M. Bowden Laboratory, Aviation & Missile Research, Development, and Engineering Center (AMRDEC), Redstone Arsenal, Alabama 35898 (United States); Everitt, Henry O. [Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005 (United States); Charles M. Bowden Laboratory, Aviation & Missile Research, Development, and Engineering Center (AMRDEC), Redstone Arsenal, Alabama 35898 (United States); Pasquali, Matteo [Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005 (United States); Department of Chemistry, Rice University, Houston, Texas 77005 (United States); Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005 (United States); Kono, Junichiro, E-mail: kono@rice.edu [Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005 (United States); Department of Materials Science and NanoEngineering, Rice University, Houston, Texas 77005 (United States); Department of Physics and Astronomy, Rice University, Houston, Texas 77005 (United States)

    2016-04-04

    Conventional, commercially available terahertz (THz) polarizers are made of uniformly and precisely spaced metallic wires. They are fragile and expensive, with performance characteristics highly reliant on wire diameters and spacings. Here, we report a simple and highly error-tolerant method for fabricating a freestanding THz polarizer with nearly ideal performance, reliant on the intrinsically one-dimensional character of conduction electrons in well-aligned carbon nanotubes (CNTs). The polarizer was constructed on a mechanical frame over which we manually wound acid-doped CNT fibers with ultrahigh electrical conductivity. We demonstrated that the polarizer has an extinction ratio of ∼−30 dB with a low insertion loss (<0.5 dB) throughout a frequency range of 0.2–1.1 THz. In addition, we used a THz ellipsometer to measure the Müller matrix of the CNT-fiber polarizer and found comparable attenuation to a commercial metallic wire-grid polarizer. Furthermore, based on the classical theory of light transmission through an array of metallic wires, we demonstrated the most striking difference between the CNT-fiber and metallic wire-grid polarizers: the latter fails to work in the zero-spacing limit, where it acts as a simple mirror, while the former continues to work as an excellent polarizer even in that limit due to the one-dimensional conductivity of individual CNTs.

  10. Polarization-preserving holey fibers

    DEFF Research Database (Denmark)

    Broeng, Jes; Mogilevtsev, Dmitri; Libori, Stig E. Barkou

    2001-01-01

    In this work we suggest and discuss a microstructure of air capillaries with elliptical cross-section in a tread of glass that gives opportunity for Creation of polarization-preserving fiber with very small beat length between the fundamental modes of different polarization...

  11. Polarized Scintillating Targets at Psi

    Science.gov (United States)

    van den Brandt, B.; Bunyatova, E. I.; Hautle, P.; Konter, J. A.; Mango, S.

    2001-02-01

    Scintillating polarized targets are now routinely available: blocks of 18×18×5 mm scintillating organic polymer, doped with TEMPO, polarized dynamically in a field of 2.5 T in a vertical 3He-4He dilution refrigerator. A 19 mm diameter plastic lightguide transports the scintillation light from the sample in the mixing chamber to a photomultiplier outside the cryostat.

  12. UV Coatings, Polarization, and Coronagraphy

    Science.gov (United States)

    Bolcar, Matthew R.; Quijada, Manuel; West, Garrett; Balasubramanian, Bala; Krist, John; Martin, Stefan; Sabatke, Derek

    2016-01-01

    Presenation for the Large UltraViolet Optical Infrared (LUVOIR) and Habitable Exoplanet Imager (HabEx) Science and Technology Definition Teams (STDT) on technical considerations regarding ultraviolet coatings, polarization, and coronagraphy. The presentations review the state-of-the-art in ultraviolet coatings, how those coatings generate polarization aberrations, and recent study results from both the LUVOIR and HabEx teams.

  13. Polarization Imaging and Insect Vision

    Science.gov (United States)

    Green, Adam S.; Ohmann, Paul R.; Leininger, Nick E.; Kavanaugh, James A.

    2010-01-01

    For several years we have included discussions about insect vision in the optics units of our introductory physics courses. This topic is a natural extension of demonstrations involving Brewster's reflection and Rayleigh scattering of polarized light because many insects heavily rely on optical polarization for navigation and communication.…

  14. Climate Drives Polar Bear Origins

    Science.gov (United States)

    In their provocative analysis of northern bears (“Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage,” Reports, 20 April, p. 344), F. Hailer et al. use independent nuclear loci to show that polar bears originated during the middle Pleistocene, rather than during t...

  15. Molecular Evolution and Functional Characterization of a Bifunctional Decarboxylase Involved in Lycopodium Alkaloid Biosynthesis1[OPEN

    Science.gov (United States)

    Bunsupa, Somnuk; Hanada, Kousuke; Maruyama, Akira; Aoyagi, Kaori; Komatsu, Kana; Ueno, Hideki; Yamashita, Madoka; Sasaki, Ryosuke; Oikawa, Akira; Yamazaki, Mami

    2016-01-01

    Lycopodium alkaloids (LAs) are derived from lysine (Lys) and are found mainly in Huperziaceae and Lycopodiaceae. LAs are potentially useful against Alzheimer’s disease, schizophrenia, and myasthenia gravis. Here, we cloned the bifunctional lysine/ornithine decarboxylase (L/ODC), the first gene involved in LA biosynthesis, from the LA-producing plants Lycopodium clavatum and Huperzia serrata. We describe the in vitro and in vivo functional characterization of the L. clavatum L/ODC (LcL/ODC). The recombinant LcL/ODC preferentially catalyzed the decarboxylation of l-Lys over l-ornithine (l-Orn) by about 5 times. Transient expression of LcL/ODC fused with the amino or carboxyl terminus of green fluorescent protein, in onion (Allium cepa) epidermal cells and Nicotiana benthamiana leaves, showed LcL/ODC localization in the cytosol. Transgenic tobacco (Nicotiana tabacum) hairy roots and Arabidopsis (Arabidopsis thaliana) plants expressing LcL/ODC enhanced the production of a Lys-derived alkaloid, anabasine, and cadaverine, respectively, thus, confirming the function of LcL/ODC in plants. In addition, we present an example of the convergent evolution of plant Lys decarboxylase that resulted in the production of Lys-derived alkaloids in Leguminosae (legumes) and Lycopodiaceae (clubmosses). This convergent evolution event probably occurred via the promiscuous functions of the ancestral Orn decarboxylase, which is an enzyme involved in the primary metabolism of polyamine. The positive selection sites were detected by statistical analyses using phylogenetic trees and were confirmed by site-directed mutagenesis, suggesting the importance of those sites in granting the promiscuous function to Lys decarboxylase while retaining the ancestral Orn decarboxylase function. This study contributes to a better understanding of LA biosynthesis and the molecular evolution of plant Lys decarboxylase. PMID:27303024

  16. 4-coumarate: CoA ligase partitions metabolites for eugenol biosynthesis.

    Science.gov (United States)

    Rastogi, Shubhra; Kumar, Ritesh; Chanotiya, Chandan S; Shanker, Karuna; Gupta, Madan M; Nagegowda, Dinesh A; Shasany, Ajit K

    2013-08-01

    Biosynthesis of eugenol shares its initial steps with that of lignin, involving conversion of hydroxycinnamic acids to their corresponding coenzyme A (CoA) esters by 4-coumarate:CoA ligases (4CLs). In this investigation, a 4CL (OS4CL) was identified from glandular trichome-rich tissue of Ocimum sanctum with high sequence similarity to an isoform (OB4CL_ctg4) from Ocimum basilicum. The levels of OS4CL and OB4CL_ctg4-like transcripts were highest in O. sanctum trichome, followed by leaf, stem and root. The eugenol content in leaf essential oil was positively correlated with the expression of OS4CL in the leaf at different developmental stages. Recombinant OS4CL showed the highest activity with p-coumaric acid, followed by ferulic, caffeic and trans-cinnamic acids. Transient RNA interference (RNAi) suppression of OS4CL in O. sanctum leaves caused a reduction in leaf eugenol content and trichome transcript level, with a considerable increase in endogenous p-coumaric, ferulic, trans-cinnamic and caffeic acids. A significant reduction in the expression levels was observed for OB4CL_ctg4-related transcripts in suppressed trichome compared with transcripts similar to the other four isoforms (OB4CL_ctg1, 2, 3 and 5). Sinapic acid and lignin content were also unaffected in RNAi suppressed leaf samples. Transient expression of OS4CL-green fluorescent protein fusion protein in Arabidopsis protoplasts was associated with the cytosol. These results indicate metabolite channeling of intermediates towards eugenol by a specific 4CL and is the first report demonstrating the involvement of 4CL in creation of virtual compartments through substrate utilization and committing metabolites for eugenol biosynthesis at an early stage of the pathway.

  17. Integrins and epithelial cell polarity.

    Science.gov (United States)

    Lee, Jessica L; Streuli, Charles H

    2014-08-01

    Cell polarity is characterised by differences in structure, composition and function between at least two poles of a cell. In epithelial cells, these spatial differences allow for the formation of defined apical and basal membranes. It has been increasingly recognised that cell-matrix interactions and integrins play an essential role in creating epithelial cell polarity, although key gaps in our knowledge remain. This Commentary will discuss the mounting evidence for the role of integrins in polarising epithelial cells. We build a model in which both inside-out signals to polarise basement membrane assembly at the basal surface, and outside-in signals to control microtubule apical-basal orientation and vesicular trafficking are required for establishing and maintaining the orientation of epithelial cell polarity. Finally, we discuss the relevance of the basal integrin polarity axis to cancer. This article is part of a Minifocus on Establishing polarity. © 2014. Published by The Company of Biologists Ltd.

  18. Hyperon polarization: An experimental overview

    International Nuclear Information System (INIS)

    Lach, J.

    1992-12-01

    The fact that inclusively produced hyperons are produced with significant polarization was first discovered at Fermilab about seventeen years ago. This and subsequent experiments showed that Λ degree were produced polarized while bar Λ degree had no polarization in the same kinematical region. This set the stage for many experiments which showed that most hyperons are produced polarized. Recent Fermilab experiments have showed that this phenomena is even more complex than previously thought and theoretical understanding is still lacking. Nevertheless polarized hyperon beams have been an extremely useful experimental tool in measuring hyperon magnetic moments and hyperon β-decay. Recently, hyperon radiative decays have been studied and magnetic moment precession of channeled particles in bent crystals has been observed

  19. A review of polarized ion sources

    International Nuclear Information System (INIS)

    Schmor, P.W.

    1995-06-01

    The two main types of polarized ion sources in use on accelerators today are the Atomic Beam Polarized Ion Source (ABIS) source and the Optically Pumped Polarized Ion Source (OPPIS). Both types can provide beams of nuclearly polarized light ions which are either positively or negatively charged. Heavy ion polarized ion sources for accelerators are being developed. (author). 35 refs., 1 tab

  20. Fluorescence Spectra of Highlighter Inks

    Science.gov (United States)

    Birriel, Jennifer J.; King, Damon

    2018-01-01

    Fluorescence spectra excited by laser pointers have been the subject of several papers in "TPT". These papers all describe a fluorescence phenomenon in which the reflected laser light undergoes a change in color: this color change results from the combination of some partially reflected laser light and additional colors generated by…

  1. ANTAGONISTIC POTENTIAL OF FLUORESCENT Pseudomonas ...

    African Journals Online (AJOL)

    Prof. Adipala Ekwamu

    This study focused on the antagonistic potential of fluorescent Pseudomonas in vitro, and its inoculation effect on growth performance of Lycopersicon esculentum in Fusarium oxysporum and Rhizoctonia solani infested soil. Biochemical characteristics of fluorescent Pseudomonas showed that all ten isolates were positive ...

  2. Assessing Photosynthesis by Fluorescence Imaging

    Science.gov (United States)

    Saura, Pedro; Quiles, Maria Jose

    2011-01-01

    This practical paper describes a novel fluorescence imaging experiment to study the three processes of photochemistry, fluorescence and thermal energy dissipation, which compete during the dissipation of excitation energy in photosynthesis. The technique represents a non-invasive tool for revealing and understanding the spatial heterogeneity in…

  3. Regulation of anthocyanin biosynthesis in peach fruits.

    Science.gov (United States)

    Rahim, Md Abdur; Busatto, Nicola; Trainotti, Livio

    2014-11-01

    MYB10.1 and MYB10.3, with bHLH3, are the likely regulators of anthocyanin biosynthesis in peach fruit. MYB10.1/2/3 forms a cluster on the same genomic fragment where the Anther color ( Ag ) trait is located. Anthocyanins are bioactive compounds responsible for the pigmentation of many plant parts such as leaves, flowers, fruits and roots, and have potential benefits to human health. In peach [Prunus persica (L.) Batsch], peel color is a key determinant for fruit quality and is regulated by flavonoids including anthocyanins. The R2R3 MYB transcription factors (TFs) control the expression of anthocyanin biosynthetic genes with the help of co-activators belonging to the basic-helix-loop-helix (bHLH) and WD40 repeat families. In the peach genome six MYB10-like and three bHLH-like TFs were identified as candidates to be the regulators of the anthocyanin accumulation, which, in yellow flesh fruits, is highest in the peel, abundant in the part of the mesocarp surrounding the stone and lowest in the mesocarp. The expression of MYB10.1 and MYB10.3 correlates with anthocyanin levels of different peach parts. They also have positive correlation with the expression of key structural genes of the anthocyanin pathway, such as CHS, F3H, and UFGT. Functions of peach MYB10s were tested in tobacco and shown to activate key genes in the anthocyanin pathway when bHLHs were co-expressed as partners. Overexpression of MYB10.1/bHLH3 and MYB10.3/bHLH3 activated anthocyanin production by up-regulating NtCHS, NtDFR and NtUFGT while other combinations were not, or much less, effective. As three MYB10 genes are localized in a genomic region where the Ag trait, responsible for anther pigmentation, is localized, it is proposed they are key determinant to introduce new peach cultivars with higher antioxidant level and pigmented fruit.

  4. Promoting Diversity Through Polar Interdisciplinary Coordinated Education (Polar ICE)

    Science.gov (United States)

    McDonnell, J. D.; Hotaling, L. A.; Garza, C.; Van Dyk, P. B.; Hunter-thomson, K. I.; Middendorf, J.; Daniel, A.; Matsumoto, G. I.; Schofield, O.

    2017-12-01

    Polar Interdisciplinary Coordinated Education (ICE) is an education and outreach program designed to provide public access to the Antarctic and Arctic regions through polar data and interactions with the scientists. The program provides multi-faceted science communication training for early career scientists that consist of a face-to face workshop and opportunities to apply these skills. The key components of the scientist training workshop include cultural competency training, deconstructing/decoding science for non-expert audiences, the art of telling science stories, and networking with members of the education and outreach community and reflecting on communication skills. Scientists partner with educators to provide professional development for K-12 educators and support for student research symposia. Polar ICE has initiated a Polar Literacy initiative that provides both a grounding in big ideas in polar science and science communication training designed to underscore the importance of the Polar Regions to the public while promoting interdisciplinary collaborations between scientists and educators. Our ultimate objective is to promote STEM identity through professional development of scientists and educators while developing career awareness of STEM pathways in Polar science.

  5. A vacuolar membrane protein affects drastically the biosynthesis of the ACV tripeptide and the beta-lactam pathway of Penicillium chrysogenum.

    Science.gov (United States)

    Fernández-Aguado, Marta; Teijeira, Fernando; Martín, Juan F; Ullán, Ricardo V

    2013-01-01

    The knowledge about enzymes' compartmentalization and transport processes involved in the penicillin biosynthesis in Penicillium chrysogenum is very limited. The genome of this fungus contains multiple genes encoding transporter proteins, but very little is known about them. A bioinformatic search was made to find major facilitator supefamily (MFS) membrane proteins related to CefP transporter protein involved in the entry of isopenicillin N to the peroxisome in Acremonium chrysogenum. No strict homologue of CefP was observed in P. chrysogenum, but the penV gene was found to encode a membrane protein that contained 10 clear transmembrane spanners and two other motifs COG5594 and DUF221, typical of membrane proteins. RNAi-mediated silencing of penV gene provoked a drastic reduction of the production of the δ-(L-α-aminoadipyl-L-cysteinyl-D-valine) (ACV) and isopenicillin N intermediates and the final product of the pathway. RT-PCR and northern blot analyses confirmed a reduction in the expression levels of the pcbC and penDE biosynthetic genes, whereas that of the pcbAB gene increased. Localization studies by fluorescent laser scanning microscopy using Dsred and GFP fluorescent fusion proteins and the FM 4-64 fluorescent dye showed clearly that the protein was located in the vacuolar membrane. These results indicate that PenV participates in the first stage of the beta-lactam biosynthesis (i.e., the formation of the ACV tripeptide), probably taking part in the supply of amino acids from the vacuolar lumen to the vacuole-anchored ACV synthetase. This is in agreement with several reports on the localization of the ACV synthetase and provides increased evidence for a compartmentalized storage of precursor amino acids for non-ribosomal peptides. PenV is the first MFS transporter of P. chrysogenum linked to the beta-lactam biosynthesis that has been located in the vacuolar membrane.

  6. Differential Polarization Nonlinear Optical Microscopy with Adaptive Optics Controlled Multiplexed Beams

    Directory of Open Access Journals (Sweden)

    Virginijus Barzda

    2013-09-01

    Full Text Available Differential polarization nonlinear optical microscopy has the potential to become an indispensable tool for structural investigations of ordered biological assemblies and microcrystalline aggregates. Their microscopic organization can be probed through fast and sensitive measurements of nonlinear optical signal anisotropy, which can be achieved with microscopic spatial resolution by using time-multiplexed pulsed laser beams with perpendicular polarization orientations and photon-counting detection electronics for signal demultiplexing. In addition, deformable membrane mirrors can be used to correct for optical aberrations in the microscope and simultaneously optimize beam overlap using a genetic algorithm. The beam overlap can be achieved with better accuracy than diffraction limited point-spread function, which allows to perform polarization-resolved measurements on the pixel-by-pixel basis. We describe a newly developed differential polarization microscope and present applications of the differential microscopy technique for structural studies of collagen and cellulose. Both, second harmonic generation, and fluorescence-detected nonlinear absorption anisotropy are used in these investigations. It is shown that the orientation and structural properties of the fibers in biological tissue can be deduced and that the orientation of fluorescent molecules (Congo Red, which label the fibers, can be determined. Differential polarization microscopy sidesteps common issues such as photobleaching and sample movement. Due to tens of megahertz alternating polarization of excitation pulses fast data acquisition can be conveniently applied to measure changes in the nonlinear signal anisotropy in dynamically changing in vivo structures.

  7. Differential polarization nonlinear optical microscopy with adaptive optics controlled multiplexed beams.

    Science.gov (United States)

    Samim, Masood; Sandkuijl, Daaf; Tretyakov, Ian; Cisek, Richard; Barzda, Virginijus

    2013-09-09

    Differential polarization nonlinear optical microscopy has the potential to become an indispensable tool for structural investigations of ordered biological assemblies and microcrystalline aggregates. Their microscopic organization can be probed through fast and sensitive measurements of nonlinear optical signal anisotropy, which can be achieved with microscopic spatial resolution by using time-multiplexed pulsed laser beams with perpendicular polarization orientations and photon-counting detection electronics for signal demultiplexing. In addition, deformable membrane mirrors can be used to correct for optical aberrations in the microscope and simultaneously optimize beam overlap using a genetic algorithm. The beam overlap can be achieved with better accuracy than diffraction limited point-spread function, which allows to perform polarization-resolved measurements on the pixel-by-pixel basis. We describe a newly developed differential polarization microscope and present applications of the differential microscopy technique for structural studies of collagen and cellulose. Both, second harmonic generation, and fluorescence-detected nonlinear absorption anisotropy are used in these investigations. It is shown that the orientation and structural properties of the fibers in biological tissue can be deduced and that the orientation of fluorescent molecules (Congo Red), which label the fibers, can be determined. Differential polarization microscopy sidesteps common issues such as photobleaching and sample movement. Due to tens of megahertz alternating polarization of excitation pulses fast data acquisition can be conveniently applied to measure changes in the nonlinear signal anisotropy in dynamically changing in vivo structures.

  8. Differential Polarization Nonlinear Optical Microscopy with Adaptive Optics Controlled Multiplexed Beams

    Science.gov (United States)

    Samim, Masood; Sandkuijl, Daaf; Tretyakov, Ian; Cisek, Richard; Barzda, Virginijus

    2013-01-01

    Differential polarization nonlinear optical microscopy has the potential to become an indispensable tool for structural investigations of ordered biological assemblies and microcrystalline aggregates. Their microscopic organization can be probed through fast and sensitive measurements of nonlinear optical signal anisotropy, which can be achieved with microscopic spatial resolution by using time-multiplexed pulsed laser beams with perpendicular polarization orientations and photon-counting detection electronics for signal demultiplexing. In addition, deformable membrane mirrors can be used to correct for optical aberrations in the microscope and simultaneously optimize beam overlap using a genetic algorithm. The beam overlap can be achieved with better accuracy than diffraction limited point-spread function, which allows to perform polarization-resolved measurements on the pixel-by-pixel basis. We describe a newly developed differential polarization microscope and present applications of the differential microscopy technique for structural studies of collagen and cellulose. Both, second harmonic generation, and fluorescence-detected nonlinear absorption anisotropy are used in these investigations. It is shown that the orientation and structural properties of the fibers in biological tissue can be deduced and that the orientation of fluorescent molecules (Congo Red), which label the fibers, can be determined. Differential polarization microscopy sidesteps common issues such as photobleaching and sample movement. Due to tens of megahertz alternating polarization of excitation pulses fast data acquisition can be conveniently applied to measure changes in the nonlinear signal anisotropy in dynamically changing in vivo structures. PMID:24022688

  9. Purine Biosynthesis Metabolically Constrains Intracellular Survival of Uropathogenic Escherichia coli

    Science.gov (United States)

    Shaffer, Carrie L.; Zhang, Ellisa W.; Dudley, Anne G.; Dixon, Beverly R. E. A.; Guckes, Kirsten R.; Breland, Erin J.; Floyd, Kyle A.; Casella, Daniel P.; Algood, Holly M. Scott; Clayton, Douglass B.

    2016-01-01

    ABSTRACT The ability to de novo synthesize purines has been associated with the intracellular survival of multiple bacterial pathogens. Uropathogenic Escherichia coli (UPEC), the predominant cause of urinary tract infections, undergoes a transient intracellular lifestyle during which bacteria clonally expand into multicellular bacterial communities within the cytoplasm of bladder epithelial cells. Here, we characterized the contribution of the conserved de novo purine biosynthesis-associated locus cvpA-purF to UPEC pathogenesis. Deletion of cvpA-purF, or of purF alone, abolished de novo purine biosynthesis but did not impact bacterial adherence properties in vitro or in the bladder lumen. However, upon internalization by bladder epithelial cells, UPEC deficient in de novo purine biosynthesis was unable to expand into intracytoplasmic bacterial communities over time, unless it was extrachromosomally complemented. These findings indicate that UPEC is deprived of purine nucleotides within the intracellular niche and relies on de novo purine synthesis to meet this metabolic requirement. PMID:27795353

  10. NAD+ biosynthesis, aging, and disease [version 1; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Sean Johnson

    2018-02-01

    Full Text Available Nicotinamide adenine dinucleotide (NAD+ biosynthesis and its regulation have recently been attracting markedly increasing interest. Aging is marked by a systemic decrease in NAD+ across multiple tissues. The dysfunction of NAD+ biosynthesis plays a critical role in the pathophysiologies of multiple diseases, including age-associated metabolic disorders, neurodegenerative diseases, and mental disorders. As downstream effectors, NAD+-dependent enzymes, such as sirtuins, are involved in the progression of such disorders. These recent studies implicate NAD+ biosynthesis as a potential target for preventing and treating age-associated diseases. Indeed, new studies have demonstrated the therapeutic potential of supplementing NAD+ intermediates, such as nicotinamide mononucleotide and nicotinamide riboside, providing a proof of concept for the development of an effective anti-aging intervention.

  11. Zincophorin – biosynthesis in Streptomyces griseus and antibiotic properties

    Directory of Open Access Journals (Sweden)

    Walther, Elisabeth

    2016-11-01

    Full Text Available Zincophorin is a polyketide antibiotic that possesses potent activity against Gram-positive bacteria, including human pathogens. While a number of total syntheses of this highly functionalized natural product were reported since its initial discovery, the genetic basis for the biosynthesis of zincophorin has remained unclear. In this study, the co-linearity inherent to polyketide pathways was used to identify the zincophorin biosynthesis gene cluster in the genome of the natural producer HKI 0741. Interestingly, the same locus is fully conserved in the streptomycin-producing actinomycete IFO 13350, suggesting that the latter bacterium is also capable of zincophorin biosynthesis. Biological profiling of zincophorin revealed a dose-dependent inhibition of the Gram-positive bacterium . The antibacterial effect, however, is accompanied by cytotoxicity. Antibiotic and cytotoxic activities were completely abolished upon esterification of the carboxylic acid group in zincophorin.

  12. Genes Involved in the Biosynthesis and Transport of Acinetobactin in

    Directory of Open Access Journals (Sweden)

    Tarik Hasan

    2015-03-01

    Full Text Available Pathogenic bacteria survive in iron-limited host environments by using several iron acquisition mechanisms. Acinetobacter baumannii, causing serious infections in compromised patients, produces an iron-chelating molecule, called acinetobactin, which is composed of equimolar quantities of 2,3-dihydroxybenzoic acid (DHBA, L-threonine, and N-hydroxyhistamine, to compete with host cells for iron. Genes that are involved in the production and transport of acinetobactin are clustered within the genome of A. baumannii. A recent study showed that entA, located outside of the acinetobactin gene cluster, plays important roles in the biosynthesis of the acinetobactin precursor DHBA and in bacterial pathogenesis. Therefore, understanding the genes that are associated with the biosynthesis and transport of acinetobactin in the bacterial genome is required. This review is intended to provide a general overview of the genes in the genome of A. baumannii that are required for acinetobactin biosynthesis and transport.

  13. Inhibitors of amino acids biosynthesis as antifungal agents.

    Science.gov (United States)

    Jastrzębowska, Kamila; Gabriel, Iwona

    2015-02-01

    Fungal microorganisms, including the human pathogenic yeast and filamentous fungi, are able to synthesize all proteinogenic amino acids, including nine that are essential for humans. A number of enzymes catalyzing particular steps of human-essential amino acid biosynthesis are fungi specific. Numerous studies have shown that auxotrophic mutants of human pathogenic fungi impaired in biosynthesis of particular amino acids exhibit growth defect or at least reduced virulence under in vivo conditions. Several chemical compounds inhibiting activity of one of these enzymes exhibit good antifungal in vitro activity in minimal growth media, which is not always confirmed under in vivo conditions. This article provides a comprehensive overview of the present knowledge on pathways of amino acids biosynthesis in fungi, with a special emphasis put on enzymes catalyzing particular steps of these pathways as potential targets for antifungal chemotherapy.

  14. Some aspects of genetic control of antibiotic biosynthesis in Streptomyces

    Directory of Open Access Journals (Sweden)

    М. P. Teplitskaya

    2005-12-01

    Full Text Available These work contain a review of basic hypotheses and experimental information in relation to the problem of antibiotic synthesis regulation by the bacteria of the Streptomyces family. Data on cluster organization of antibiotics biosynthesis genes in these microorganisms were generalized. The examples of the positive and negative specific control of antibiotic production genes were resulted. Except for it, proofs that confirm participation of a few genes of more high level in the process of initiation and expression of antibiotics biosynthesis genes also were found. In this connection А-factor role in the mechanism of cascade-organized process of streptomycin biosynthesis control, some other antibiotics and spore determinations is discussed in detail.

  15. Time-resolved fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Gustavsson, Thomas; Mialocq, Jean-Claude

    2007-01-01

    This article addresses the evolution in time of light emitted by a molecular system after a brief photo-excitation. The authors first describe fluorescence from a photo-physical point of view and discuss the characterization of the excited state. Then, they explain some basic notions related to fluorescence characterization (lifetime and decays, quantum efficiency, so on). They present the different experimental methods and techniques currently used to study time-resolved fluorescence. They discuss basic notions of time resolution and spectral reconstruction. They briefly present some conventional methods: intensified Ccd cameras, photo-multipliers and photodiodes associated with a fast oscilloscope, and phase modulation. Other methods and techniques are more precisely presented: time-correlated single photon counting (principle, examples, and fluorescence lifetime imagery), streak camera (principle, examples), and optical methods like the Kerr optical effect (principle and examples) and fluorescence up-conversion (principle and theoretical considerations, examples of application)

  16. Spectral, stoichiometric ratio, physicochemical, polarity and photostability studies of newly synthesized chalcone dye in organized media

    Energy Technology Data Exchange (ETDEWEB)

    Marwani, Hadi M., E-mail: hmarwani@kau.edu.sa [Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia); Center of Excellence for Advanced Materials Research, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia); Asiri, Abdullah M. [Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia); Center of Excellence for Advanced Materials Research, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia); Khan, Salman A. [Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589 (Saudi Arabia)

    2013-04-15

    The main focus of this study was to investigate spectroscopic properties, stoichiometric ratios, physicochemical parameters, polarity and photostability behaviors of newly synthesized chalcone dye in organized media. The chalcone dye, 1-(2,5-Dimethyl-thiophen-3-yl)-3-(9-etnyl-9H-carbazol-3-yl)-propenone (DTEP), was prepared by the reaction of carbazole aldehyde with 3-acetyl-2,5-dimethythiophene. Data obtained from FT-IR, {sup 1}H-–NMR, {sup 13}C-NMR and elemental analysis were consistent with chemical structure of newly prepared DTEP. Increases in fluorescence intensities of DTEP with cetyltrimethyl ammonium bromide (CTAB) were observed. In comparison of fluorescence intensities for DTEP with CTAB, reductions in fluorescence intensities for DTEP with sodium dodecyl sulfate (SDS) were noticed under the same experimental and instrumental conditions. Additionally, Benesi–Hildebrand method was applied to determine stoichiometric ratios and association constants of DTEP with CTAB and SDS. Stern–Volmer plot was used in order to further confirm the stoichiometric ratio and association constant of DTEP with SDS. Physicochemical parameters such as singlet absorption, molar absorptivity, oscillator strength, dipole moment and fluorescence quantum yield of DTEP were also determined. Fluorescence polarity study displayed that DTEP was sensitive to the polarity of the microenvironment provided by different solvents. Finally, fluorescence steady-state measurements revealed that DTEP has high photostability against photobleaching. -- Highlights: ► Mechanistic understanding of molecular structure of newly synthesized chalcone dye. ► Exploring spectral behaviors and physicochemical parameters of chalcone dye. ► Determination of stoichiometric ratios and association constants of chalcone dye. ► Determination of fluorescence quantum yield in different solvents. ► High photostability against photobleaching of chalcone dye was observed.

  17. Spectral, stoichiometric ratio, physicochemical, polarity and photostability studies of newly synthesized chalcone dye in organized media

    International Nuclear Information System (INIS)

    Marwani, Hadi M.; Asiri, Abdullah M.; Khan, Salman A.

    2013-01-01

    The main focus of this study was to investigate spectroscopic properties, stoichiometric ratios, physicochemical parameters, polarity and photostability behaviors of newly synthesized chalcone dye in organized media. The chalcone dye, 1-(2,5-Dimethyl-thiophen-3-yl)-3-(9-etnyl-9H-carbazol-3-yl)-propenone (DTEP), was prepared by the reaction of carbazole aldehyde with 3-acetyl-2,5-dimethythiophene. Data obtained from FT-IR, 1 H-–NMR, 13 C-NMR and elemental analysis were consistent with chemical structure of newly prepared DTEP. Increases in fluorescence intensities of DTEP with cetyltrimethyl ammonium bromide (CTAB) were observed. In comparison of fluorescence intensities for DTEP with CTAB, reductions in fluorescence intensities for DTEP with sodium dodecyl sulfate (SDS) were noticed under the same experimental and instrumental conditions. Additionally, Benesi–Hildebrand method was applied to determine stoichiometric ratios and association constants of DTEP with CTAB and SDS. Stern–Volmer plot was used in order to further confirm the stoichiometric ratio and association constant of DTEP with SDS. Physicochemical parameters such as singlet absorption, molar absorptivity, oscillator strength, dipole moment and fluorescence quantum yield of DTEP were also determined. Fluorescence polarity study displayed that DTEP was sensitive to the polarity of the microenvironment provided by different solvents. Finally, fluorescence steady-state measurements revealed that DTEP has high photostability against photobleaching. -- Highlights: ► Mechanistic understanding of molecular structure of newly synthesized chalcone dye. ► Exploring spectral behaviors and physicochemical parameters of chalcone dye. ► Determination of stoichiometric ratios and association constants of chalcone dye. ► Determination of fluorescence quantum yield in different solvents. ► High photostability against photobleaching of chalcone dye was observed

  18. Recent advances in combinatorial biosynthesis for drug discovery

    Directory of Open Access Journals (Sweden)

    Sun H

    2015-02-01

    Full Text Available Huihua Sun,1,* Zihe Liu,1,* Huimin Zhao,1,2 Ee Lui Ang1 1Metabolic Engineering Research Laboratory, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research, Singapore; 2Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA *These authors contributed equally to this work Abstract: Because of extraordinary structural diversity and broad biological activities, natural products have played a significant role in drug discovery. These therapeutically important secondary metabolites are assembled and modified by dedicated biosynthetic pathways in their host living organisms. Traditionally, chemists have attempted to synthesize natural product analogs that are important sources of new drugs. However, the extraordinary structural complexity of natural products sometimes makes it challenging for traditional chemical synthesis, which usually involves multiple steps, harsh conditions, toxic organic solvents, and byproduct wastes. In contrast, combinatorial biosynthesis exploits substrate promiscuity and employs engineered enzymes and pathways to produce novel “unnatural” natural products, substantially expanding the structural diversity of natural products with potential pharmaceutical value. Thus, combinatorial biosynthesis provides an environmentally friendly way to produce natural product analogs. Efficient expression of the combinatorial biosynthetic pathway in genetically tractable heterologous hosts can increase the titer of the compound, eventually resulting in less expensive drugs. In this review, we will discuss three major strategies for combinatorial biosynthesis: 1 precursor-directed biosynthesis; 2 enzyme-level modification, which includes swapping of the entire domains, modules and subunits, site-specific mutagenesis, and directed evolution; 3 pathway-level recombination. Recent examples of combinatorial biosynthesis employing these

  19. Characterization of the Fluorescence Properties of 4-Dialkylaminochalcones and Investigation of the Cytotoxic Mechanism of Chalcones.

    Science.gov (United States)

    Zhou, Bo; Jiang, Peixin; Lu, Junxuan; Xing, Chengguo

    2016-07-01

    Understanding the mechanisms responsible for the various biological activities of chalcones, particularly the direct cellular targets, presents an unmet challenge. Here, we prepared a series of fluorescent chalcone derivatives as chemical probes for their mechanistic investigation. Upon systematic physicochemical characterization, we explored their potential to elucidate the mode of action of chalcones' cytotoxicity. The fluorescence of the chalcones was found to be highly sensitive to structural and environmental factors. Structurally, a 4-dialkylamino group on the B ring, suitable electronic properties of the A ring substituents, and the planar conformation of the chalcone's core structure were essential for optimal fluorescence. Environmental factors influencing fluorescence included solvent polarity, pH, and the interactions of the chalcones with proteins and detergents. It was found that 18 chalcones showed a fluorescent brightness greater than 6000 M(-1)  cm(-1) in DMSO. However, water dramatically quenched the fluorescence, although it could be partially recovered in the presence of BSA or detergents. As expected, these fluorescent chalcones showed a sharp structure-activity relationship in their cellular cytotoxicity, leading to the identification of structurally similar cytotoxic and non-cytotoxic fluorescent chalcones as chemical probes. Confocal microscopy results revealed the co-localization of the cytotoxic probe C8 and tubulin in cells, supporting tubulin as the direct cellular target responsible for the cytotoxicity of chalcones. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Studies of the laser-induced fluorescence of explosives and explosive compositions.

    Energy Technology Data Exchange (ETDEWEB)

    Hargis, Philip Joseph, Jr. (,; .); Thorne, Lawrence R.; Phifer, Carol Celeste; Parmeter, John Ethan; Schmitt, Randal L.

    2006-10-01

    Continuing use of explosives by terrorists throughout the world has led to great interest in explosives detection technology, especially in technologies that have potential for standoff detection. This LDRD was undertaken in order to investigate the possible detection of explosive particulates at safe standoff distances in an attempt to identify vehicles that might contain large vehicle bombs (LVBs). The explosives investigated have included the common homogeneous or molecular explosives, 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclonite or hexogen (RDX), octogen (HMX), and the heterogeneous explosive, ammonium nitrate/fuel oil (ANFO), and its components. We have investigated standard excited/dispersed fluorescence, laser-excited prompt and delayed dispersed fluorescence using excitation wavelengths of 266 and 355 nm, the effects of polarization of the laser excitation light, and fluorescence imaging microscopy using 365- and 470-nm excitation. The four nitro-based, homogeneous explosives (TNT, PETN, RDX, and HMX) exhibit virtually no native fluorescence, but do exhibit quenching effects of varying magnitude when adsorbed on fluorescing surfaces. Ammonium nitrate and fuel oil mixtures fluoresce primarily due to the fuel oil, and, in some cases, due to the presence of hydrophobic coatings on ammonium nitrate prill or impurities in the ammonium nitrate itself. Pure ammonium nitrate shows no detectable fluorescence. These results are of scientific interest, but they provide little hope for the use of UV-excited fluorescence as a technique to perform safe standoff detection of adsorbed explosive particulates under real-world conditions with a useful degree of reliability.

  1. POLARIZED LIGHT IN PHYSIOTHERAPY

    Directory of Open Access Journals (Sweden)

    L. D. Tondiy

    2015-12-01

    Full Text Available The data on polarized light (PS - a new promising treatment, rehabilitation and prevention, which took its deserved place among the known therapeutic physical factors and may even compete with laser radiation of low and LED therapy. It is reflected the significant contribution of domestic scientists in the study of aircraft action on the body, its introduction in the treatment, rehabilitation and prevention of grippe, ARI. These action's mechanisms of the aircraft on the electro-physiological processes in the body that have the leading role in the regulation of its life. The new moment in the study of aircraft on the body is the evidence of its positive impact on the mechanisms of self body - its different units: the disease's banning - a revitalization of the stress-protective, stress-limiting system antioxidial, detoxification and other protection systems, the formation by the body antiviral and antimicrobial specific substances (interferon and lysozyme, activation of the immune system, phagocytosis, protective functions of skin. The protective and mobilizing role of the second link is studied: which is triggered in case of occurrence of disease or preexisting diseases: PL mobilized processes of restitution, reparations, compensation, immunity and microcirculation. The authors studied the possibility of aircraft's using to enhance performance, reduce side effects of physical factors, which are often used in the treatment (electric methods, treatment by sound, fresh and mineral water, etc..

  2. Update of the Polar SWIFT model for polar stratospheric ozone loss (Polar SWIFT version 2)

    Science.gov (United States)

    Wohltmann, Ingo; Lehmann, Ralph; Rex, Markus

    2017-07-01

    The Polar SWIFT model is a fast scheme for calculating the chemistry of stratospheric ozone depletion in polar winter. It is intended for use in global climate models (GCMs) and Earth system models (ESMs) to enable the simulation of mutual interactions between the ozone layer and climate. To date, climate models often use prescribed ozone fields, since a full stratospheric chemistry scheme is computationally very expensive. Polar SWIFT is based on a set of coupled differential equations, which simulate the polar vortex-averaged mixing ratios of the key species involved in polar ozone depletion on a given vertical level. These species are O3, chemically active chlorine (ClOx), HCl, ClONO2 and HNO3. The only external input parameters that drive the model are the fraction of the polar vortex in sunlight and the fraction of the polar vortex below the temperatures necessary for the formation of polar stratospheric clouds. Here, we present an update of the Polar SWIFT model introducing several improvements over the original model formulation. In particular, the model is now trained on vortex-averaged reaction rates of the ATLAS Chemistry and Transport Model, which enables a detailed look at individual processes and an independent validation of the different parameterizations contained in the differential equations. The training of the original Polar SWIFT model was based on fitting complete model runs to satellite observations and did not allow for this. A revised formulation of the system of differential equations is developed, which closely fits vortex-averaged reaction rates from ATLAS that represent the main chemical processes influencing ozone. In addition, a parameterization for the HNO3 change by denitrification is included. The rates of change of the concentrations of the chemical species of the Polar SWIFT model are purely chemical rates of change in the new version, whereas in the original Polar SWIFT model, they included a transport effect caused by the

  3. Final Report on Regulation of Guaiacyl and Syringyl Monolignol Biosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Vincent L. Chiang

    2006-03-09

    The focus of this research is to understand syringyl monolignol biosynthesis that leads to the formation of syringyl lignin, a type of lignin that can be easily removed during biomass conversion. We have achieved the three originally proposed goals for this project. (1) SAD and CAD genes (enzyme catalytic and kinetic properties) and their functional relevance to CAld5H/AldOMT pathway, (2) spatiotemporal expression patterns of Cald5H, AldOMT, SAD and CAD genes, and (3) functions of CAld5H, AldOMT, and SAD genes in vivo using transgenic aspen. Furthermore, we also found that microRNA might be involved in the upstream regulatory network of lignin biosynthesis and wood formation. The achievements are as below. (1) Based on biochemical and molecular studies, we discovered a novel syringyl-specific alcohol dehydrogenase (SAD) involved in monolignol biosynthesis in angiosperm trees. Through CAld5H/OMT/SAD mediation, syringyl monolignol biosynthesis branches out from guaiacyl pathway at coniferaldehyde; (2) The function of CAld5H gene in this syringyl monolignol biosynthesis pathway also was confirmed in vivo in transgenic Populus; (3) The proposed major monolignol biosynthesis pathways were further supported by the involving biochemical functions of CCR based on a detailed kinetic study; (4) Gene promoter activity analysis also supported the cell-type specific expression of SAD and CAD genes in xylem tissue, consistent with the cell-specific locations of SAD and CAD proteins and with the proposed pathways; (5) We have developed a novel small interfering RNA (siRNA)-mediated stable gene-silencing system in transgenic plants; (6) Using the siRNA and P. trichocarpa transformation/regeneration systems we are currently producing transgenic P. trichocarpa to investigate the interactive functions of CAD and SAD in regulating guaiacyl and syringyl lignin biosynthesis; (7) We have cloned for the first time from a tree species, P. trichocarpa, small regulatory RNAs termed micro

  4. Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

    Directory of Open Access Journals (Sweden)

    Franziska Hemmerling

    2016-07-01

    Full Text Available This review highlights the biosynthesis of heterocycles in polyketide natural products with a focus on oxygen and nitrogen-containing heterocycles with ring sizes between 3 and 6 atoms. Heterocycles are abundant structural elements of natural products from all classes and they often contribute significantly to their biological activity. Progress in recent years has led to a much better understanding of their biosynthesis. In this context, plenty of novel enzymology has been discovered, suggesting that these pathways are an attractive target for future studies.

  5. Topical problems in the biosynthesis of red blood pigment

    International Nuclear Information System (INIS)

    Franck, B.

    1982-01-01

    Uroporphyrinogen III plays a key role in the biosynthesis of heme, the red pigment of blood. In vivo studies with specifically 14 C- and 3 H-labeled precursors have revealed that the formation of uroporphyrinogen III in the organism follows several primary and subsidiary pathways. Model experiments on the pattern of biosynthesis have led to simple and effective methods of synthesizing uroporphyrin analogs and have shwon that their production is strongly favored thermodynamically, The biologically important porphyrins thus available permit a mechanistic explanantion of the light-induced dermatoses in porphyria diseases and suggest promising medical applications in diagnosis and therapy. (orig.)

  6. Carbon extension in peptidylnucleoside biosynthesis by radical-SAM enzymes

    Science.gov (United States)

    Lilla, Edward A.; Yokoyama, Kenichi

    2016-01-01

    Nikkomycins and polyoxins are antifungal peptidylnucleoside (PN) antibiotics active against human and plant pathogens. Here, we report that during PN biosynthesis in Streptomyces cacaoi and Streptomyces tendae, the C5′-extension of the nucleoside essential for downstream structural diversification is catalyzed by a conserved radical S-adenosyl-L-methionine (SAM) enzyme, PolH or NikJ. This is distinct from the nucleophilic mechanism reported for antibacterial nucleosides and represents a novel mechanism of nucleoside natural product biosynthesis. PMID:27642865

  7. Phosphoribosyl Diphosphate (PRPP): Biosynthesis, Enzymology, Utilization, and Metabolic Significance

    DEFF Research Database (Denmark)

    Hove-Jensen, Bjarne; Andersen, Kasper R; Kilstrup, Mogens

    2017-01-01

    . PRPP is utilized in the biosynthesis of purine and pyrimidine nucleotides, the amino acids histidine and tryptophan, the cofactors NAD and tetrahydromethanopterin, arabinosyl monophosphodecaprenol, and certain aminoglycoside antibiotics. The participation of PRPP in each of these metabolic pathways...... analysis. PRPP, furthermore, is an effector molecule of purine and pyrimidine nucleotide biosynthesis, either by binding to PurR or PyrR regulatory proteins or as an allosteric activator of carbamoylphosphate synthetase. Genetic analyses have disclosed a number of mutants altered in the PRPP synthase...

  8. [Biosynthesis of benzoisochromanequinones antibiotics from streptomycetes--a review].

    Science.gov (United States)

    Wang, Wei; Wang, Huili; Li, Aiying

    2012-05-04

    Benzoisochromanequinones antibiotics, a group of bioactive polyketide compounds with aromatic polyketide skeletal cores, are accumulated in streptomycetes. The biosynthesis of benzoisochromanequinones antibiotics has triggered great interest because they not only represent model biosynthetic mechanisms of aromatic polyketide skeletal structures, but also possess a variety of tailoring modifications rendering them highly structural and bioactive diversity. Here we reviewed important advances in biosynthesis of benzoisochromanequinones antibiotics in recent 25 years with focusing on the modification mechanisms of these compounds and on the prospects of the metabolic engineering and pharmaceutical discovery of benzoisochromanequinones antibiotics.

  9. Structure, Biosynthesis, and Occurrence of Bacterial Pyrrolizidine Alkaloids.

    Science.gov (United States)

    Schimming, Olivia; Challinor, Victoria L; Tobias, Nicholas J; Adihou, Hélène; Grün, Peter; Pöschel, Laura; Richter, Christian; Schwalbe, Harald; Bode, Helge B

    2015-10-19

    Pyrrolizidine alkaloids (PAs) are widespread plant natural products with potent toxicity and bioactivity. Herein, the identification of bacterial PAs from entomopathogenic bacteria using differential analysis by 2D NMR spectroscopy (DANS) and mass spectrometry is described. Their biosynthesis was elucidated to involve a non-ribosomal peptide synthetase. The occurrence of these biosynthesis gene clusters in Gram-negative and Gram-positive bacteria indicates an important biological function in bacteria. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Insect monitoring with fluorescence lidar techniques: feasibility study.

    Science.gov (United States)

    Brydegaard, Mikkel; Guan, Zuguang; Wellenreuther, Maren; Svanberg, Sune

    2009-10-20

    We investigate the possibilities of light detection and ranging (lidar) techniques to study migration of the damselfly species Calopteryx splendens and C. virgo. Laboratory and testing-range measurements at a distance of 60 m were performed using dried, mounted damselfly specimens. Laboratory measurements, including color photography in polarized light and spectroscopy of reflectance and induced fluorescence, reveal that damselflies exhibit reflectance and fluorescence properties that are closely tied to the generation of structural color. Lidar studies on C. splendens of both genders show that gender can be remotely determined, especially for specimens that were marked with Coumarin 102 and Rhodamine 6G dyes. The results obtained in this study will be useful for future field experiments, and provide guidelines for studying damselflies in their natural habitat using lidar to survey the air above the river surface. The findings will be applicable for many other insect species and should, therefore, bring new insights into migration and movement patterns of insects in general.

  11. Fluorescence microscopy imaging of electroperturbation in mammalian cells.

    Science.gov (United States)

    Sun, Yinghua; Vernier, P Thomas; Behrend, Matthew; Wang, Jingjing; Thu, Mya Mya; Gundersen, Martin; Marcu, Laura

    2006-01-01

    We report the design, integration, and validation of a fluorescence microscopy system for imaging of electroperturbation--the effects of nanosecond, megavolt-per-meter pulsed electric fields on biological cells and tissues. Such effects have potential applications in cancer therapy, gene regulation, and biophysical research by noninvasively disrupting intracellular compartments and inducing apoptosis in malignant cells. As the primary observing platform, an epifluorescence microscope integrating a nanosecond high-voltage pulser and a micrometer electrode chamber enable in situ imaging of the intracellular processes triggered by high electric fields. Using specific fluorescence molecular probes, the dynamic biological responses of Jurkat T lymphocytes to nanosecond electric pulses (nanoelectropulses) are studied with this system, including calcium bursts, the polarized translocation of phosphatidylserine (PS), and nuclear enlargement and chromatin/DNA structural changes.

  12. Shedding Some Light on Fluorescent Bulbs.

    Science.gov (United States)

    Guilbert, Nicholas R.

    1996-01-01

    Explores some of the principles behind the working of fluorescent bulbs using a specially prepared fluorescent bulb with the white inner fluorescent coating applied along only half its length. Discusses the spectrum, the bulb plasma, and light production. (JRH)

  13. Single Molecule Spectroscopy of Fluorescent Proteins

    NARCIS (Netherlands)

    Blum, Christian; Subramaniam, Vinod

    2009-01-01

    The discovery and use of fluorescent proteins has revolutionized cellular biology. Despite the widespread use of visible fluorescent proteins as reporters and sensors in cellular environments the versatile photophysics of fluorescent proteins is still subject to intense research. Understanding the

  14. Direct probing of chromatography columns by laser-induced fluorescence

    Energy Technology Data Exchange (ETDEWEB)

    McGuffin, V.L.

    1992-12-07

    This report summarizes the progress and accomplishments of this research project from September 1, 1989 to February 28, 1993. During this period, we have accomplished all of the primary scientific objectives of the research proposal: (1) constructed and evaluated a laser-induced fluorescence detection system that allows direct examination of the chromatographic column, (2) examined nonequilibrium processes that occur upon solute injection and elution, (3) examined solute retention in liquid chromatography as a function of temperature and pressure, (4) examined solute zone dispersion in liquid chromatography as a function of temperature and pressure, and (5) developed appropriate theoretical models to describe these phenomena. In each of these studies, substantial knowledge has been gained of the fundamental processes that are responsible for chromatographic separations. In addition to these primary research objectives, we have made significant progress in three related areas: (1) examined pyrene as a fluorescent polarity probe insupercritical fluids and liquids as a function of temperature and pressure, (2) developed methods for the class-selective identification of polynuclear aromatic hydrocarbons in coal-derived fluids by microcolumn liquid chromatography with fluorescence quenching detection, and (3) developed methods for the determination of saturated and unsaturated (including omega-3) fatty acids in fish oil extracts by microcolumn liquid chromatography with laser-induced fluorescence detection. In these studies, the advanced separation and detection techniques developed in our laboratory are applied to practical problems of environmental and biomedical significance.

  15. Fluorescence properties of Ag nanoparticles in water, methanol and hexane

    Energy Technology Data Exchange (ETDEWEB)

    Siwach, Om Parkash [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Sen, P. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi 110067 (India)], E-mail: psen0700@mail.jnu.ac.in

    2009-01-15

    Ag nanoparticles, synthesized employing the electro-exploding wire technique, are reported. Absorption in the UV-visible region by these particles is characterized by the features reported in the literature, namely, a possible plasmon peak at {approx}404 nm. For Ag nanoparticles dispersed in water, photo-excitation in the ranges 210-235 and 255-280 nm produces similar fluorescence emission at {approx}300 nm, whose corresponding resonant absorption takes place at 215 and 270 nm in the excitation spectra. Further, we study the effect of the surrounding medium (solvent effect) on fluorescence from these nanoparticles by comparing fluorescence emission in methanol and hexane for photo-excitation in the same range. Compared to water, fluorescence emission in methanol is observed red-shifted at {approx}310 nm, which further red-shifts to {approx}325 nm in hexane. The corresponding resonant absorptions in methanol are at 225 and 275 nm. Consequence of this red-shift in a less polar solvent is discussed.

  16. Nuclear physics with polarized particles

    CERN Document Server

    Paetz gen Schieck, Hans

    2012-01-01

    The measurement of spin-polarization observables in reactions of nuclei and particles is of great utility and advantage when the effects of single-spin sub-states are to be investigated. Indeed, the unpolarized differential cross-section encompasses the averaging over the spin states of the particles, and thus loses details of the interaction process. This introductory text combines, in a single volume, course-based lecture notes on spin physics and on polarized-ion sources with the aim of providing a concise yet self-contained starting point for newcomers to the field, as well as for lecturers in search of suitable material for their courses and seminars. A significant part of the book is devoted to introducing the formal theory-a description of polarization and of nuclear reactions with polarized particles. The remainder of the text describes the physical basis of methods and devices necessary to perform experiments with polarized particles and to measure polarization and polarization effects in nuclear rea...

  17. Online observation of emulsion polymerization by fluorescence technique

    CERN Document Server

    Rudschuck, S; Fuhrmann, J

    1999-01-01

    An online observation of local polarity via fluorescence spectroscopy was used to study the formation and growth of polymer particles during an emulsifier-free heterogeneous polymerization. The reaction mixture consisted of styrene dispersed in water and the polymerization was initiated by a macro-initiator (hydrolyzed propene-maleic acid copolymer with t-butyl perester groups). Pyrenyl probes were attached to the backbone of the initiator to analyze the heterogeneous reaction. The experimental results allow a clear distinction of different time regions during the heterogeneous polymerization. Information about the heating period, the latex formation, the particle growth and the final stage of the polymerization process (gel point) were obtained. (11 refs).

  18. Few-body experiments with polarized beams and polarized targets

    International Nuclear Information System (INIS)

    Simmons, J.E.

    1983-01-01

    A survey is presented concerning recent polarization experiments in the elastic p-d, p- 3 He, and p- 4 He systems. Mention is made of selected neutron experiments. The nominal energy range is 10 to 1000 MeV. Recent results and interpretations of the p-d system near 10 MeV are discussed. New experiments on the energy dependence of back angle p-d tensor polarization are discussed with respect to resolution of discrepancies and difficulty of theoretical interpretation. Progress is noted concerning multiple scattering interpretation of forward p-d deuteron polarization. Some new results are presented concerning the p- 3 He system and higher energy p- 4 He polarization experiments. 52 references

  19. Fluorescently labeled substrates for monitoring α1,3-fucosyltransferase IX activity.

    Science.gov (United States)

    Lunau, Nathalie; Seelhorst, Katrin; Kahl, Stefanie; Tscherch, Kathrin; Stacke, Christina; Rohn, Sascha; Thiem, Joachim; Hahn, Ulrich; Meier, Chris

    2013-12-16

    Fucosylation is often the final process in glycan biosynthesis. The resulting glycans are involved in a variety of biological processes, such as cell adhesion, inflammation, or tumor metastasis. Fucosyltransferases catalyze the transfer of fucose residues from the activated donor molecule GDP-β-L-fucose to various acceptor molecules. However, detailed information about the reaction processes is still lacking for most fucosyltransferases. In this work we have monitored α1,3-fucosyltransferase activity. For both donor and acceptor substrates, the introduction of a fluorescent ATTO dye was the last step in the synthesis. The subsequent conversion of these substrates into fluorescently labeled products by α1,3-fucosyltransferases was examined by high-performance thin-layer chromatography coupled with mass spectrometry as well as dual-color fluorescence cross-correlation spectroscopy, which revealed that both fluorescently labeled donor GDP-β-L-fucose-ATTO 550 and acceptor N-acetyllactosamine-ATTO 647N were accepted by recombinant human fucosyltransferase IX and Helicobacter pylori α1,3-fucosyltransferase, respectively. Analysis by fluorescence cross-correlation spectroscopy allowed a quick and versatile estimation of the progress of the enzymatic reaction and therefore this method can be used as an alternative method for investigating fucosyltransferase reactions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Elite Polarization and Public Opinion

    DEFF Research Database (Denmark)

    Robison, Joshua; Mullinix, Kevin

    2016-01-01

    Elite polarization has reshaped American politics and is an increasingly salient aspect of news coverage within the United States. As a consequence, a burgeoning body of research attempts to unravel the effects of elite polarization on the mass public. However, we know very little about how...... attitudes. In our first study, we show that criticism of polarization leads partisans to more positively evaluate the argument offered by their non-preferred party, increases support for bi-partisanship, but ultimately does not change the extent to which partisans follow their party’s policy endorsements...

  1. Acceleration of polarized proton beams

    International Nuclear Information System (INIS)

    Roser, T.

    1998-01-01

    The acceleration of polarized beams in circular accelerators is complicated by the numerous depolarizing spin resonances. Using a partial Siberian snake and a rf dipole that ensure stable adiabatic spin motion during acceleration has made it possible to accelerate polarized protons to 25 GeV at the Brookhaven AGS. Full Siberian snakes are being developed for RHIC to make the acceleration of polarized protons to 250 GeV possible. A similar scheme is being studied for the 800 GeV HERA proton accelerator

  2. Polarimetry with azimuthally polarized light

    Science.gov (United States)

    de Sande, Juan Carlos González; Piquero, Gemma; Santarsiero, Massimo

    2018-03-01

    Nonuniformly polarized light can be used for Mueller polarimetry of homogeneous linear samples. In this work, a set up based on using azimuthally polarized input light and a modified commercial light polarimeter is proposed and developed. With this set up, a Mueller submatrix of a sample can be obtained by measuring the Stokes parameters at only three different positions across the output beam section. Symmetry constraints for linear deterministic samples allow the complete Mueller matrix to be deduced for this kind of specimens. The experimental results obtained for phase plates and for a linear polarizer confirm the validity of the proposed method.

  3. Polarized deuteron elastic scattering from a polarized proton target

    International Nuclear Information System (INIS)

    Schmelzer, R.; Kuiper, H.; Schoeberl, M.; Berber, S.; Hilmert, H.; Koeppel, R.; Pferdmenges, R.; Zankel, H.

    1983-01-01

    Measurements are reported of the spin correlation parameter Cy,y for the elastic scattering of 10.0 MeV vector polarized deuterons from a polarized proton target at five CM angles (76 0 ,85 0 ,98 0 ,115 0 ,132 0 ). The experimental results are compared with different predictions. A Faddeev type calculation on the basis of local potentials also including approximate Coulomb distortion is favoured by our experimental results. (orig.)

  4. PolarHub: A Global Hub for Polar Data Discovery

    Science.gov (United States)

    Li, W.

    2014-12-01

    This paper reports the outcome of a NSF project in developing a large-scale web crawler PolarHub to discover automatically the distributed polar dataset in the format of OGC web services (OWS) in the cyberspace. PolarHub is a machine robot; its goal is to visit as many webpages as possible to find those containing information about polar OWS, extract this information and store it into the backend data repository. This is a very challenging task given huge data volume of webpages on the Web. Three unique features was introduced in PolarHub to make it distinctive from earlier crawler solutions: (1) a multi-task, multi-user, multi-thread support to the crawling tasks; (2) an extensive use of thread pool and Data Access Object (DAO) design patterns to separate persistent data storage and business logic to achieve high extendibility of the crawler tool; (3) a pattern-matching based customizable crawling algorithm to support discovery of multi-type geospatial web services; and (4) a universal and portable client-server communication mechanism combining a server-push and client pull strategies for enhanced asynchronous processing. A series of experiments were conducted to identify the impact of crawling parameters to the overall system performance. The geographical distribution pattern of all PolarHub identified services is also demonstrated. We expect this work to make a major contribution to the field of geospatial information retrieval and geospatial interoperability, to bridge the gap between data provider and data consumer, and to accelerate polar science by enhancing the accessibility and reusability of adequate polar data.

  5. Fluorescent standards for photodynamic therapy

    Science.gov (United States)

    Belko, N.; Kavalenka, S.; Samtsov, M.

    2016-08-01

    Photodynamic therapy is an evolving technique for treatment of various oncological diseases. This method employs photosensitizers - species that lead to death of tumor cells after the photoactivation. For further development and novel applications of photodynamic therapy new photosensitizers are required. After synthesis of a new photosensitizer it is important to know its concentration in different biological tissues after its administration and distribution. The concentration is frequently measured by the extraction method, which has some disadvantages, e.g. it requires many biological test subjects that are euthanized during the measurement. We propose to measure the photosensitizer concentration in tissue by its fluorescence. For this purpose fluorescent standards were developed. The standards are robust and simple to produce; their fluorescence signal does not change with time. The fluorescence intensity of fluorescent standards seems to depend linearly on the dye concentration. A set of standards thus allow the calibration of a spectrometer. Finally, the photosensitizer concentration can be determined by the fluorescence intensity after comparing the corresponding spectrum with spectra of the set of fluorescent standards. A biological test subject is not euthanized during this kind of experiment. We hope this more humane technique can be used in future instead of the extraction method.

  6. Biosynthesis of allene oxides in Physcomitrella patens

    Directory of Open Access Journals (Sweden)

    Scholz Julia

    2012-11-01

    Full Text Available Abstract Background The moss Physcomitrella patens contains C18- as well as C20-polyunsaturated fatty acids that can be metabolized by different enzymes to form oxylipins such as the cyclopentenone cis(+-12-oxo phytodienoic acid. Mutants defective in the biosynthesis of cyclopentenones showed reduced fertility, aberrant sporophyte morphology and interrupted sporogenesis. The initial step in this biosynthetic route is the conversion of a fatty acid hydroperoxide to an allene oxide. This reaction is catalyzed by allene oxide synthase (AOS belonging as hydroperoxide lyase (HPL to the cytochrome P450 family Cyp74. In this study we characterized two AOS from P. patens, PpAOS1 and PpAOS2. Results Our results show that PpAOS1 is highly active with both C18 and C20-hydroperoxy-fatty acid substrates, whereas PpAOS2 is fully active only with C20-substrates, exhibiting trace activity (~1000-fold lower kcat/KM with C18 substrates. Analysis of products of PpAOS1 and PpHPL further demonstrated that both enzymes have an inherent side activity mirroring the close inter-connection of AOS and HPL catalysis. By employing site directed mutagenesis we provide evidence that single amino acid residues in the active site are also determining the catalytic activity of a 9-/13-AOS – a finding that previously has only been reported for substrate specific 13-AOS. However, PpHPL cannot be converted into an AOS by exchanging the same determinant. Localization studies using YFP-labeled AOS showed that PpAOS2 is localized in the plastid while PpAOS1 may be found in the cytosol. Analysis of the wound-induced cis(+-12-oxo phytodienoic acid accumulation in PpAOS1 and PpAOS2 single knock-out mutants showed that disruption of PpAOS1, in contrast to PpAOS2, results in a significantly decreased cis(+-12-oxo phytodienoic acid formation. However, the knock-out mutants of neither PpAOS1 nor PpAOS2 showed reduced fertility, aberrant sporophyte morphology or interrupted sporogenesis

  7. Status report of the S-DALINAC polarized electron injector SPIN at Darmstadt

    Energy Technology Data Exchange (ETDEWEB)

    Eckardt, Christian; Bahlo, Thore; Bangert, Phillip; Barday, Roman; Bonnes, Uwe; Brunken, Marco; Eichhorn, Ralf; Enders, Joachim; Platz, Markus; Poltoratska, Yuliya; Roth, Markus; Schneider, Fabian; Wagner, Markus; Weber, Antje; Zwicker, Benjamin [Institut fuer Kernphysik, Technische Universitaet Darmstadt (Germany); Ackermann, Wolfgang; Mueller, Wolfgang F.O.; Weiland, Thomas [Institut fuer Theorie Elektromagnetischer Felder, Technische Universitaet Darmstadt (Germany)

    2010-07-01

    At the superconducting 130 MeV Darmstadt electron linac S-DALINAC a source of polarized electrons is being installed. Polarized electrons are produced by photoemission from a negative electron affinity strained superlattice GaAs cathode and preaccelerated to 100 keV. With a Wien filter and Mott polarimeter in the beam line the polarization is manipulated and measured. For beam diagnostics wire scanners, fluorescent screens and a coaxial Faraday cup are included. To measure the beam polarization at higher energies, a 5-10 MeV Mott polarimeter and a 50-130 MeV Moeller polarimeter as well as a Compton transmission polarimeter will be installed. We report on the status of the implementation and show plans for future development and experiments.

  8. Single-Molecule Fluorescence Studies of Membrane Transporters Using Total Internal Reflection Microscopy.

    Science.gov (United States)

    Goudsmits, Joris M H; van Oijen, Antoine M; Slotboom, Dirk J

    2017-01-01

    Cells are delineated by a lipid bilayer that physically separates the inside from the outer environment. Most polar, charged, or large molecules require proteins to reduce the energetic barrier for passage across the membrane and to achieve transport rates that are relevant for life. Here, we describe techniques to visualize the functioning of membrane transport proteins with fluorescent probes at the single-molecule level. First, we explain how to produce membrane-reconstituted transporters with fluorescent labels. Next, we detail the construction of a microfluidic flow cell to image immobilized proteoliposomes on a total internal reflection fluorescence microscope. We conclude by describing the methods that are needed to analyze fluorescence movies and obtain useful single-molecule data. © 2017 Elsevier Inc. All rights reserved.

  9. Photoinduced electron transfer and fluorescence mechanisms in covalently linked polynuclear aromatic-nucleotide complexes

    Energy Technology Data Exchange (ETDEWEB)

    Geacintov, N.E.; Mao, Bing; Zhao, Rushen; Chen, Junxin; Liu, Tong Ming; Ya, Nai-Qi (New York Univ., NY (United States). Dept. of Chemistry); France, L.L.; Sutherland, J.D. (Brookhaven National Lab., Upton, NY (United States))

    1992-01-01

    The fluorescence of polycyclic aromatic hydrocarbon-nucleic acid complexes is quenched by photoinduced electron transfer mechanisms in aqueous solutions at ambient temperatures. These effects are illustrated with the biologically important compound benzo(a)pyrene-7,8-diol-9,10-epoxide (BPDE), a mutagenic and carcinogenic metabolite of the environmental pollutant benzo(a)pyrene, which forms covalent mutagenic lesions with 2{prime}-deoxyguanosine (dG) residues in DNA. The dependence of the fluroescence yeild and fluorescence decay times of the covalent model adduct (+)-trans-BPDE-N{sup 2}-dG as a function of temperature and methanol/water composition are described. Because of the sensitivity of the fluorescence of the pyrenyl residue to the polarity of the microenvironment, the magnitude of the fluorescence yield can be used to distinguish between highly hydrophobic (e.g. intercalation) and other more solvent-exposed BPDE-nucleic acid binding sites.

  10. Photoinduced electron transfer and fluorescence mechanisms in covalently linked polynuclear aromatic-nucleotide complexes

    Energy Technology Data Exchange (ETDEWEB)

    Geacintov, N.E.; Mao, Bing; Zhao, Rushen; Chen, Junxin; Liu, Tong Ming; Ya, Nai-Qi [New York Univ., NY (United States). Dept. of Chemistry; France, L.L.; Sutherland, J.D. [Brookhaven National Lab., Upton, NY (United States)

    1992-04-01

    The fluorescence of polycyclic aromatic hydrocarbon-nucleic acid complexes is quenched by photoinduced electron transfer mechanisms in aqueous solutions at ambient temperatures. These effects are illustrated with the biologically important compound benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), a mutagenic and carcinogenic metabolite of the environmental pollutant benzo[a]pyrene, which forms covalent mutagenic lesions with 2{prime}-deoxyguanosine (dG) residues in DNA. The dependence of the fluroescence yeild and fluorescence decay times of the covalent model adduct (+)-trans-BPDE-N{sup 2}-dG as a function of temperature and methanol/water composition are described. Because of the sensitivity of the fluorescence of the pyrenyl residue to the polarity of the microenvironment, the magnitude of the fluorescence yield can be used to distinguish between highly hydrophobic (e.g. intercalation) and other more solvent-exposed BPDE-nucleic acid binding sites.

  11. Polar source analysis : technical memorandum

    Science.gov (United States)

    2017-09-29

    The following technical memorandum describes the development, testing and analysis of various polar source data sets. The memorandum also includes recommendation for potential inclusion in future releases of AEDT. This memorandum is the final deliver...

  12. Anodic Concentration Polarization in SOFCs

    Energy Technology Data Exchange (ETDEWEB)

    Williford, Rick E.; Chick, Lawrence A.; Maupin, Gary D.; Simner, Steve P.; Stevenson, Jeffry W.; Khaleel, Mohammad A.; Wachsman, ED, et al

    2003-08-01

    Concentration polarization is important because it determines the maximum power output of a solid oxide fuel cell (SOFC) at high fuel utilization. Anodic concentration polarization occurs when the demand for reactants exceeds the capacity of the porous ceramic anode to supply them by gas diffusion mechanisms. High tortuosities (bulk diffusion resistances) are often assumed to explain this behavior. However, recent experiments show that anodic concentration polarization originates in the immediate vicinity of the reactive triple phase boundary (TPB) sites near the anode/electrolyte interface. A model is proposed to describe how concentration polarization is controlled by two localized phenomena: competitive adsorption of reactants in areas adjacent to the reactive TPB sites, followed by relatively slow surface diffusion to the reactive sites. Results suggest that future SOFC design improvements should focus on optimization of the reactive area, adsorption, and surface diffusion at the anode/electrolyte interface.

  13. The definition of cross polarization

    DEFF Research Database (Denmark)

    Ludwig, Arthur

    1973-01-01

    There are at least three different definitions of cross polarization used in the literature. The alternative definitions are discussed with respect to several applications, and the definition which corresponds to one standard measurement practice is proposed as the best choice....

  14. Dynamic elections and ideological polarization

    Czech Academy of Sciences Publication Activity Database

    Nunnari, S.; Zápal, Jan

    2017-01-01

    Roč. 25, č. 4 (2017), s. 505-534 ISSN 1047-1987 Institutional support: Progres-Q24 Keywords : elections * political polarization Subject RIV: AH - Economics OBOR OECD: Economic Theory Impact factor: 3.361, year: 2016

  15. Dynamic elections and ideological polarization

    Czech Academy of Sciences Publication Activity Database

    Nunnari, S.; Zápal, Jan

    2017-01-01

    Roč. 25, č. 4 (2017), s. 505-534 ISSN 1047-1987 Institutional support: RVO:67985998 Keywords : elections * political polarization Subject RIV: AH - Economics OBOR OECD: Economic Theory Impact factor: 3.361, year: 2016

  16. Polarization at LEP. Vol. 2

    International Nuclear Information System (INIS)

    Alexander, G.; Altarelli, G.; Blondel, A.; Coignet, G.; Keil, E.; Plane, D.E.; Treille, D.

    1988-01-01

    This report contains a collection of papers covering the most important part of studies carried out by five study groups in view of a programme of experiments with polarized beams at LEP, the Large Electron-Positron collider under construction at CERN. The emphasis is on precision measurements at the Z peak. Such measurements are shown to be of considerable theoretical interest as well as very clean from the point of view of theoretical and experimental uncertainties. The measurement of the beam polarization can certainly be performed with sufficient accuracy, thanks to the availability of both e + and e - beam polarization. The normalization of the data taken with different beam helicities poses certain constraints that are described. Substantial progress has been made in understanding the possibility of providing longitudinally polarized beams in the LEP machine: The design of new wigglers and spin rotators, the study of correction procedures and results of numerical simulations are presented. (orig.)

  17. Mechanical writing of ferroelectric polarization.

    Science.gov (United States)

    Lu, H; Bark, C-W; Esque de los Ojos, D; Alcala, J; Eom, C B; Catalan, G; Gruverman, A

    2012-04-06

    Ferroelectric materials are characterized by a permanent electric dipole that can be reversed through the application of an external voltage, but a strong intrinsic coupling between polarization and deformation also causes all ferroelectrics to be piezoelectric, leading to applications in sensors and high-displacement actuators. A less explored property is flexoelectricity, the coupling between polarization and a strain gradient. We demonstrate that the stress gradient generated by the tip of an atomic force microscope can mechanically switch the polarization in the nanoscale volume of a ferroelectric film. Pure mechanical force can therefore be used as a dynamic tool for polarization control and may enable applications in which memory bits are written mechanically and read electrically.

  18. Mechanical Writing of Ferroelectric Polarization

    Science.gov (United States)

    Lu, H.; Bark, C.-W.; Esque de los Ojos, D.; Alcala, J.; Eom, C. B.; Catalan, G.; Gruverman, A.

    2012-04-01

    Ferroelectric materials are characterized by a permanent electric dipole that can be reversed through the application of an external voltage, but a strong intrinsic coupling between polarization and deformation also causes all ferroelectrics to be piezoelectric, leading to applications in sensors and high-displacement actuators. A less explored property is flexoelectricity, the coupling between polarization and a strain gradient. We demonstrate that the stress gradient generated by the tip of an atomic force microscope can mechanically switch the polarization in the nanoscale volume of a ferroelectric film. Pure mechanical force can therefore be used as a dynamic tool for polarization control and may enable applications in which memory bits are written mechanically and read electrically.

  19. Chemical structure, biosynthesis and synthesis of free and glycosylated pyridinolines formed by cross-link of bone and synovium collagen.

    Science.gov (United States)

    Anastasia, Luigi; Rota, Paola; Anastasia, Mario; Allevi, Pietro

    2013-09-21

    This review focuses on the chemical structure, biosynthesis and synthesis of free and glycosylated pyridinolines (Pyds), fluorescent collagen cross-links, with a pyridinium salt structure. Pyds derive from the degradation of bone collagen and have attracted attention for their use as biochemical markers of bone resorption and to assess fracture risk prediction in persons suffering from osteoporosis, bone cancer and other bone or collagen diseases. We consider and critically discuss all reported syntheses of free and glycosylated Pyds evidencing an unrevised chemistry, original and of general utility, analysis of which allows us to also support a previously suggested non-enzymatic formation of Pyds in collagen better rationalizing and justifying the chemical events.

  20. Involvement of inositol biosynthesis and nitric oxide in the mediation of UV-B induced oxidative stress

    Directory of Open Access Journals (Sweden)

    Dmytro I Lytvyn

    2016-04-01

    Full Text Available The involvement of NO-signaling in ultraviolet B (UV-B induced oxidative stress in plants is an open question. Inositol biosynthesis contributes to numerous cellular functions, including the regulation of plants tolerance to stress. This work reveals the involvement of inositol-3-phosphate synthase 1 (IPS1, a key enzyme for biosynthesis of myo-inositol and its derivatives, in the response to NO-dependent oxidative stress in Arabidopsis. Homozygous mutants deficient for IPS1 (atips1 and wild-type plants were transformed with a reduction-oxidation-sensitive green fluorescent protein 2 (grx1-rogfp2 and used for the dynamic measurement of UV-B-induced and SNP (sodium nitroprusside-mediated oxidative stresses by confocal microscopy. atips1 mutants displayed greater tissue-specific resistance to the action of UV-B than the wild type. SNP can act both as an oxidant or repairer depending on the applied concentration, but mutant plants were more tolerant than the wild type to nitrosative effects of high concentration of SNP. Additionally, pretreatment with low concentrations of SNP (10, 100 μM before UV-B irradiation resulted in a tissue-specific protective effect that was enhanced in atips1. We conclude that the interplay between nitric oxide and inositol signaling can be involved in the mediation of UV-B-initiated oxidative stress in the plant cell.

  1. Association with AflR in Endosomes Reveals New Functions for AflJ in Aflatoxin Biosynthesis

    Directory of Open Access Journals (Sweden)

    John E. Linz

    2012-12-01

    Full Text Available Aflatoxins are the most potent naturally occurring carcinogens of fungal origin. Biosynthesis of aflatoxin involves the coordinated expression of more than 25 genes. The function of one gene in the aflatoxin gene cluster, aflJ, is not entirely understood but, because previous studies demonstrated a physical interaction between the Zn2Cys6 transcription factor AflR and AflJ, AflJ was proposed to act as a transcriptional co-activator. Image analysis revealed that, in the absence of aflJ in A. parasiticus, endosomes cluster within cells and near septa. AflJ fused to yellow fluorescent protein complemented the mutation in A. parasiticus ΔaflJ and localized mainly in endosomes. We found that AflJ co-localizes with AflR both in endosomes and in nuclei. Chromatin immunoprecipitation did not detect AflJ binding at known AflR DNA recognition sites suggesting that AflJ either does not bind to these sites or binds to them transiently. Based on these data, we hypothesize that AflJ assists in AflR transport to or from the nucleus, thus controlling the availability of AflR for transcriptional activation of aflatoxin biosynthesis cluster genes. AflJ may also assist in directing endosomes to the cytoplasmic membrane for aflatoxin export.

  2. [Advances and prospects of taxol biosynthesis by endophytic fungi].

    Science.gov (United States)

    Zhao, Kai; Yu, Lu; Jin, Yuyan; Ma, Xueling; Liu, Dan; Wang, Xiaohua; Wang, Xin

    2016-08-25

    Taxol is one of the most important chemotherapeutic drugs against cancer. Taxol has been mainly extracted from the bark of yews for a long time. However, methods for the extraction of taxol from the bark of Taxus species were inefficient and environmentally costly. As a result of the high ecological toll exacted on trees with the potential for Pacific yew extinction, investigators began to look for other methods of taxol production. Recently, increasing efforts have been made to develop alternative means of taxol production, such as using complete chemical synthesis, semi-synthesis, Taxus spp. plant cell culture and microbe fermentation. Using microbe fermentation in the production of taxol would be a very prospective method for obtaining a large amount of taxol. Therefore, it is necessary to understand the molecular basis and genetic regulation mechanisms of taxol biosynthesis by endophytic fungi, which may be helpful to construct the genetic engineering strain with high taxol output. In this paper, the taxol biosynthesis pathway from Taxus cells and the advantages of taxol biosynthesis by endophytic fungi were discussed. The study on the isolation and biodiversity of taxol-producing endophytic fungi and the taxol biosynthesis related genes are also discussed.

  3. Regulation of Isoprenoid Pheromone Biosynthesis in Bumblebee Males

    Czech Academy of Sciences Publication Activity Database

    Prchalová, Darina; Buček, Aleš; Brabcová, Jana; Žáček, Petr; Kindl, Jiří; Valterová, Irena; Pichová, Iva

    2016-01-01

    Roč. 17, č. 3 (2016), s. 260-267 ISSN 1439-4227 R&D Projects: GA MŠk LO1302; GA ČR GA15-06569S Institutional support: RVO:61388963 Keywords : biosynthesis * Bombus spp. * gene expression * isoprenoids * pheromones * transcriptional regulation Subject RIV: CE - Biochemistry Impact factor: 2.847, year: 2016

  4. Biosynthesis of the red antibiotic, prodigiosin, in Serratia

    DEFF Research Database (Denmark)

    Williamson, Neil R; Simonsen, Henrik Toft; Ahmed, Raef A A

    2005-01-01

    from Serratia sp. ATCC 39006. The biosynthetic intermediates accumulating in each mutant have been analysed by LC-MS, cross-feeding and genetic complementation studies. Based on these results we assign specific roles in the biosynthesis of MBC to the following Pig proteins: PigI, PigG, PigA, PigJ, Pig...

  5. Biosynthesis of lipophilic compounds in tomato fruit | Angaman ...

    African Journals Online (AJOL)

    A study performed with chromoplasts to know the origin of the precursors for carotenoids biosynthesis using a variety of 14C-labelled precursors showed that the most important incorporation was found in lipids. This study aims to understand the biochemical and metabolic processes operating during tomato fruit ripening.

  6. Temporal expression of genes involved in the biosynthesis of ...

    African Journals Online (AJOL)

    Jane

    2011-10-10

    Oct 10, 2011 ... Gibberellins (GAs) are a large family of endogenous plant growth regulators. Bioactive GAs influence nearly all processes during plant growth and development. In the present study, we cloned and identified 10 unique genes that are potentially involved in the biosynthesis of GAs, including one. BpGGDP ...

  7. Biosynthesis of silver nanoparticles and its antibacterial activity ...

    African Journals Online (AJOL)

    In the present research work, biosynthesis of silver nanoparticles and its activity on bacterial pathogens were investigated. Silver nanoparticles were rapidly synthesized using Urospora sp. and the formation of nanoparticles was observed within 30 min. The results recorded from UV–vis spectrum, Fourier Transform Infrared ...

  8. The magnesium chelation step in chlorophyll biosynthesis. Progress report 1993

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, J.D.

    1993-12-31

    Progress is reported on the identification and fractionation of Magnesium chealatase, an enzyme involved in addition of Mg to chlorophyll during the later`s biosynthesis. Progress is documented as a series of synopsis of published and unpublished papers by the author.

  9. Molecular and biochemical studies of fragrance biosynthesis in rose

    NARCIS (Netherlands)

    Sun, P.

    2017-01-01

    Roses are one of the most popular ornamental plants, whose floral volatiles are not only involved in environmental interactions but also widely used by industries. The biosynthesis of many of these volatiles in roses is not well understood. This thesis describes alternative pathways for the

  10. Biosynthesis of polyketides by trans-AT polyketide synthases.

    OpenAIRE

    Helfrich Eric J N; Piel Jörn

    2016-01-01

    This review discusses the biosynthesis of natural products that are generated by trans AT polyketide synthases a family of catalytically versatile enzymes that represents one of the major group of proteins involved in the production of bioactive polyketides. The article includes 609 references and covers the literature from 2009 through June 2015.

  11. Biosynthesis of polyketides by trans-AT polyketide synthases.

    Science.gov (United States)

    Helfrich, Eric J N; Piel, Jörn

    2016-02-01

    This review discusses the biosynthesis of natural products that are generated by trans-AT polyketide synthases, a family of catalytically versatile enzymes that represents one of the major group of proteins involved in the production of bioactive polyketides. The article includes 609 references and covers the literature from 2009 through June 2015.

  12. Biosynthesis of cellulolytic enzymes by Tricothecium roseum with ...

    African Journals Online (AJOL)

    Among various soluble carbon and complex nitrogen sources tested in this study, carboxymethylcellulose and peptone supported maximum production of both cellulolytic enzymes. Under all suitable growth conditions, the enzyme biosynthesis was remarkably increased when the inducer citric acid was added to the PDYE ...

  13. Anthocyanin biosynthesis in fruit tree crops: Genes and their regulation

    African Journals Online (AJOL)

    The anthocyanin biosynthesis pathway is a little complex with branches responsible for the synthesis of a variety of metabolites. In fruit tree crops, during the past decade, many structural genes encoding enzymes in the anthocyanin biosynthetic pathway and various regulatory genes encoding transcription factors that ...

  14. Temporal expression of genes involved in the biosynthesis of ...

    African Journals Online (AJOL)

    Gibberellins (GAs) are a large family of endogenous plant growth regulators. Bioactive GAs influence nearly all processes during plant growth and development. In the present study, we cloned and identified 10 unique genes that are potentially involved in the biosynthesis of GAs, including one BpGGDP gene, two BpCPS ...

  15. Expression profiles of genes involved in tanshinone biosynthesis of ...

    Indian Academy of Sciences (India)

    Expression profiles of genes involved in tanshinone biosynthesis of two. Salvia miltiorrhiza genotypes with different tanshinone contents. Zhenqiao Song, Jianhua Wang and Xingfeng Li. J. Genet. 95, 433–439. Table 1. S. miltiorrhiza genes and primer pairs used for qRT-PCR. Gene. GenBank accession. Primer name.

  16. Biosynthesis of silver nanoparticles by Leishmania tropica | Rahi ...

    African Journals Online (AJOL)

    A novel biosynthesis route for Silver Nanoparticles (Ag-NPs) was attempted in the present study using Leishmania tropica the causative agent of cutaneous leishmaniasis in different countries, particularly in Mediterranean region in Iraq. Silver nanoparticles were successfully synthesized from AgNO3 by reduction of ...

  17. Biosynthesis and Characterization of Silver Nanoparticles by Aspergillus Species

    Directory of Open Access Journals (Sweden)

    Kamiar Zomorodian

    2016-01-01

    Full Text Available Currently, researchers turn to natural processes such as using biological microorganisms in order to develop reliable and ecofriendly methods for the synthesis of metallic nanoparticles. In this study, we have investigated extracellular biosynthesis of silver nanoparticles using four Aspergillus species including A. fumigatus, A. clavatus, A. niger, and A. flavus. We have also analyzed nitrate reductase activity in the studied species in order to determine the probable role of this enzyme in the biosynthesis of silver nanoparticles. The formation of silver nanoparticles in the cell filtrates was confirmed by the passage of laser light, change in the color of cell filtrates, absorption peak at 430 nm in UV-Vis spectra, and atomic force microscopy (AFM. There was a logical relationship between the efficiencies of studied Aspergillus species in the production of silver nanoparticles and their nitrate reductase activity. A. fumigatus as the most efficient species showed the highest nitrate reductase activity among the studied species while A. flavus exhibited the lowest capacity in the biosynthesis of silver nanoparticles which was in accord with its low nitrate reductase activity. The present study showed that Aspergillus species had potential for the biosynthesis of silver nanoparticles depending on their nitrate reductase activity.

  18. Biosynthesis and Characterization of Silver Nanoparticles by Aspergillus Species

    Science.gov (United States)

    Pourshahid, Seyedmohammad; Mehryar, Pouyan; Pakshir, Keyvan; Rahimi, Mohammad Javad; Arabi Monfared, Ali

    2016-01-01

    Currently, researchers turn to natural processes such as using biological microorganisms in order to develop reliable and ecofriendly methods for the synthesis of metallic nanoparticles. In this study, we have investigated extracellular biosynthesis of silver nanoparticles using four Aspergillus species including A. fumigatus, A. clavatus, A. niger, and A. flavus. We have also analyzed nitrate reductase activity in the studied species in order to determine the probable role of this enzyme in the biosynthesis of silver nanoparticles. The formation of silver nanoparticles in the cell filtrates was confirmed by the passage of laser light, change in the color of cell filtrates, absorption peak at 430 nm in UV-Vis spectra, and atomic force microscopy (AFM). There was a logical relationship between the efficiencies of studied Aspergillus species in the production of silver nanoparticles and their nitrate reductase activity. A. fumigatus as the most efficient species showed the highest nitrate reductase activity among the studied species while A. flavus exhibited the lowest capacity in the biosynthesis of silver nanoparticles which was in accord with its low nitrate reductase activity. The present study showed that Aspergillus species had potential for the biosynthesis of silver nanoparticles depending on their nitrate reductase activity. PMID:27652264

  19. Hacking an Algal Transcription Factor for Lipid Biosynthesis.

    Science.gov (United States)

    Chen, Xiulai; Hu, Guipeng; Liu, Liming

    2018-03-01

    Transcriptional engineering is a viable means for engineering microalgae to produce lipid, but it often results in a trade-off between production and growth. A recent study shows that engineering a single transcriptional regulator enables efficient carbon partitioning to lipid biosynthesis with high biomass productivity. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Arogenate Dehydratase Isoforms Differentially Regulate Anthocyanin Biosynthesis in Arabidopsis thaliana.

    Science.gov (United States)

    Chen, Qingbo; Man, Cong; Li, Danning; Tan, Huijuan; Xie, Ye; Huang, Jirong

    2016-12-05

    Anthocyanins, a group of L-phenylalanine (Phe)-derived flavonoids, have been demonstrated to play important roles in plant stress resistance and interactions between plants and insects. Although the anthocyanin biosynthetic pathway and its regulatory mechanisms have been extensively studied, it remains unclear whether the level of Phe supply affects anthocyanin biosynthesis. Here, we investigated the roles of arogenate dehydratases (ADTs), the key enzymes that catalyze the conversion of arogenate into Phe, in sucrose-induced anthocyanin biosynthesis in Arabidopsis. Genetic analysis showed that all six ADT isoforms function redundantly in anthocyanin biosynthesis but have differential contributions. ADT2 contributes the most to anthocyanin accumulation, followed by ADT1 and ADT3, and ADT4-ADT6. We found that anthocyanin content is positively correlated with the levels of Phe and sucrose-induced ADT transcripts in seedlings. Consistently, addition of Phe to the medium could dramatically increase anthocyanin content in the wild-type plants and rescue the phenotype of the adt1 adt3 double mutant regarding the anthocyanin accumulation. Moreover, transgenic plants overexpressing ADT4, which appears to be less sensitive to Phe than overexpression of ADT2, hyperaccumulate Phe and produce elevated level of anthocyanins. Taken together, our results suggest that the level of Phe is an important regulatory factor for sustaining anthocyanin biosynthesis. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.