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Sample records for chlorophyll fluorescence quenching

  1. Quenching of chlorophyll fluorescence induced by silver nanoparticles

    Science.gov (United States)

    Queiroz, A. M.; Mezacasa, A. V.; Graciano, D. E.; Falco, W. F.; M'Peko, J.-C.; Guimarães, F. E. G.; Lawson, T.; Colbeck, I.; Oliveira, S. L.; Caires, A. R. L.

    2016-11-01

    The interaction between chlorophyll (Chl) and silver nanoparticles (AgNPs) was evaluated by analyzing the optical behavior of Chl molecules surrounded by different concentrations of AgNPs (10, 60, and 100 nm of diameter). UV-Vis absorption, steady state and time-resolved fluorescence measurements were performed for Chl in the presence and absence of these nanoparticles. AgNPs strongly suppressed the Chl fluorescence intensity at 678 nm. The Stern-Volmer constant (KSV) showed that fluorescence suppression is driven by the dynamic quenching process. In particular, KSV was nanoparticle size-dependent with an exponential decrease as a function of the nanoparticle diameter. Finally, changes in the Chl fluorescence lifetime in the presence of nanoparticles demonstrated that the fluorescence quenching may be induced by the excited electron transfer from the Chl molecules to the metal nanoparticles.

  2. Role of formation of statistical aggregates in chlorophyll fluorescence concentration quenching.

    Science.gov (United States)

    Shi, Wu-Jun; Barber, James; Zhao, Yang

    2013-04-18

    Using extensive Monte Carlo simulations, a comprehensive investigation has been carried out on the phenomenon of chlorophyll fluorescence concentration quenching. Our results reveal that statistical aggregations of chlorophylls act mainly as trapping sites for excitation energy and lead to fluorescence quenching. Due to transition dipolar-dipolar interactions between the chlorophylls within a statistical aggregate, the associated oscillator strength changes in comparison to a monomer, and excited energy states show splitting. Further, as the lower energy states are more likely associated with lower oscillator strengths, the fluorescence intensity is observed to decrease. Due to the rapid energy transfer between chlorophyll molecules after photoexcitation, the excitonic energy can easily reach a statistical aggregate, where trapping of the exciton and its subsequent decay occur. With an increase in the chlorophyll concentration, the probability of statistical aggregation increases, thereby accentuating the fluorescence quenching effect.

  3. Carotenoid-chlorophyll coupling and fluorescence quenching correlate with protein packing density in grana-thylakoids.

    Science.gov (United States)

    Holleboom, Christoph-Peter; Yoo, Sunny; Liao, Pen-Nan; Compton, Ian; Haase, Winfried; Kirchhoff, Helmut; Walla, Peter Jomo

    2013-09-26

    The regulation of light-harvesting in photosynthesis under conditions of varying solar light irradiation is essential for the survival and fitness of plants and algae. It has been proposed that rearrangements of protein distribution in the stacked grana region of thylakoid membranes connected to changes in the electronic pigment-interaction play a key role for this regulation. In particular, carotenoid-chlorophyll interactions seem to be crucial for the down-regulation of photosynthetic light-harvesting. So far, it has been difficult to determine the influence of the dense protein packing found in native photosynthetic membrane on these interactions. We investigated the changes of the electronic couplings between carotenoids and chlorophylls and the quenching in grana thylakoids of varying protein packing density by two-photon spectroscopy, conventional chlorophyll fluorometry, low-temperature fluorescence spectroscopy, and electron micrographs of freeze-fracture membranes. We observed an increasing carotenoid-chlorophyll coupling and fluorescence quenching with increasing packing density. Simultaneously, the antennas size and excitonic connectivity of Photosystem II increased with increasing quenching and carotenoid-chlorophyll coupling whereas isolated, decoupled LHCII trimers decreased. Two distinct quenching data regimes could be identified that show up at different protein packing densities. In the regime corresponding to higher protein packing densities, quenching is strongly correlated to carotenoid-chlorophyll interactions whereas in the second regime, a weak correlation is apparent with low protein packing densities. Native membranes are in the strong-coupling data regime. Consequently, PSII and LHCII in grana membranes of plants are already quenched by protein crowding. We concluded that this ensures efficient electronic connection of all pigment-protein complexes for intermolecular energy transfer to the reaction centers and allows simultaneously

  4. Simple replacement of violaxanthin by zeaxanthin in LHC-II does not cause chlorophyll fluorescence quenching.

    Science.gov (United States)

    Dreuw, Andreas; Wormit, Michael

    2008-03-01

    Recently, a mechanism for the energy-dependent component (qE) of non-photochemical quenching (NPQ), the fundamental photo-protection mechanism in green plants, has been suggested. Replacement of violaxanthin by zeaxanthin in the binding pocket of the major light harvesting complex LHC-II may be sufficient to invoke efficient chlorophyll fluorescence quenching. Our quantum chemical calculations, however, show that the excited state energies of violaxanthin and zeaxanthin are practically identical when their geometry is constrained to the naturally observed structure of violaxanthin in LHC-II. Therefore, since violaxanthin does not quench LHC-II, zeaxanthin should not either. This theoretical finding is nicely in agreement with experimental results obtained by femtosecond spectroscopy on LHC-II complexes containing violaxanthin or zeaxanthin.

  5. Correlation of electronic carotenoid-chlorophyll interactions and fluorescence quenching with the aggregation of native LHC II and chlorophyll deficient mutants

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Pen-Nan; Bode, Stefan [Technische Universitaet Braunschweig, Institute for Physical and Theoretical Chemistry, Department for Biophysical Chemistry, Hans-Sommer-Strasse 10, 38106 Braunschweig (Germany); Wilk, Laura [Max Planck Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main (Germany); Hafi, Nour [Technische Universitaet Braunschweig, Institute for Physical and Theoretical Chemistry, Department for Biophysical Chemistry, Hans-Sommer-Strasse 10, 38106 Braunschweig (Germany); Walla, Peter J., E-mail: pwalla@gwdg.de [Technische Universitaet Braunschweig, Institute for Physical and Theoretical Chemistry, Department for Biophysical Chemistry, Hans-Sommer-Strasse 10, 38106 Braunschweig (Germany); Max Planck Institute for Biophysical Chemistry, Department of Spectroscopy and Photochemical Kinetics, Am Fassberg 11, 37077 Goettingen (Germany)

    2010-07-19

    The aggregation dependent correlation between fluorescence quenching and the electronic carotenoid-chlorophyll interactions, {phi}{sub Coupling}{sup Car S{sub 1}-Chl}, as measured by comparing chlorophyll fluorescence observed after two- and one-photon excitation, has been investigated using native LHC II samples as well as mutants lacking Chl 2 and Chl 13. For native LHC II the same linear correlation between {phi}{sub Coupling}{sup Car S{sub 1}-Chl} and the fluorescence quenching was observed as previously reported for the pH and Zea-dependent quenching of LHC II . In order to elucidate which carotenoid-chlorophyll pair might dominate this correlation we also investigated the mutants lacking Chl 2 and Chl 13. However, also with these mutants the same linear correlation as for native LHC II was observed. This provides indication that these two chlorophylls play only a minor role for the observed effects. Nevertheless, we also conclude that this does not exclude that their neighboured carotenoids, lutein 1 and neoxanthin, might interact electronically with other chlorophylls close by.

  6. O2-dependent electron flow, membrane energization and the mechanism of non-photochemical quenching of chlorophyll fluorescence.

    Science.gov (United States)

    Schreiber, U; Neubauer, C

    1990-09-01

    Recent progress in chlorophyll fluorescence research is reviewed, with emphasis on separation of photochemical and non-photochemical quenching coefficients (qP and qN) by the 'saturation pulse method'. This is part of an introductory talk at the Wageningen Meeting on 'The use of chlorophyll fluorescence and other non-invasive techniques in plant stress physiology'. The sequence of events is investigated which leads to down-regulation of PS II quantum yield in vivo, expressed in formation of qN. The role of O2-dependent electron flow for ΔpH- and qN-formation is emphasized. Previous conclusions on the rate of 'pseudocyclic' transport are re-evaluated in view of high ascorbate peroxidase activity observed in intact chloroplasts. It is proposed that the combined Mehler-Peroxidase reaction is responsible for most of the qN developed when CO2-assimilation is limited. Dithiothreitol is shown to inhibit part of qN-formation as well as peroxidase-induced electron flow. As to the actual mechanism of non-photochemical quenching, it is demonstrated that quenching is favored by treatments which slow down reactions at the PS II donor side. The same treatments are shown to stimulate charge recombination, as measured via 50 μs luminescence. It is suggested that also in vivo internal thylakoid acidification leads to stimulation of charge recombination, although on a more rapid time scale. A unifying model is proposed, incorporating reaction center and antenna quenching, with primary control of ΔpH at the PS II reaction center, involving radical pair spin transition and charge recombination to the triplet state in a first quenching step. In a second step, triplet excitation is trapped by zeaxanthin (if present) which in its triplet excited state causes additional quenching of singlet excited chlorophyll.

  7. On the polyphasic quenching kinetics of chlorophyll a fluorescence in algae after light pulses of variable length.

    Science.gov (United States)

    Vredenberg, Wim; Prasil, Ondrej

    2013-11-01

    This study reports on kinetics of the fluorescence decay in a suspension of the alga Scenedesmus quadricauda after actinic illumination. These are monitored as the variable fluorescence signal in the dark following light pulses of variable intensity and duration. The decay reflects the restoration of chlorophyll fluorescence quenching of the photosystem II (PSII) antennas and shows a polyphasic pattern which suggests the involvement of different processes. The overall quenching curve after a fluorescence-saturating pulse (SP) of 250-ms duration, commonly used in pulse amplitude modulation applications as the tool for estimating the maximal fluorescence (F m), has been termed P-O, in which P and O have the same meaning as used in the OJIP induction curve in the light. Deconvolution of this signal shows at least three distinguishable exponential phases with reciprocal rate constants of the order of 10, 10(2), and 10(3) ms. The size of the long (>10(3) ms) and moderate (~10(2) ms) lasting components relative to the complete quenching signal after an SP increases with the duration of the actinic pulse concomitantly with an increase in the reciprocal rate constants of the fast (~10 ms) and moderate quenching phases. Fluorescence responses upon single turnover flashes of 30-μs duration (STFs) given at discrete times during the P-O quenching were used as tools for identifying the quencher involved in the P-O quenching phase preceding the STF excitation. Results are difficult to interpret in terms of a single-hit two-state trapping mechanism with distinguishable quenching properties of open and closed reaction centers only. They give support for an earlier hypothesis on a double-hit three-state trapping mechanism in which the so-called semi-closed reaction centers of PSII are considered. In these trapping-competent centers the single reduced acceptor pair [PheQ A](1-), depending on the size of photoelectrochemically induced pH effects on the Q B-binding site

  8. Chemical bonding of chlorophylls and plant aminic axial ligands impact harvesting of visible light and quenching of fluorescence.

    Science.gov (United States)

    Ioannidis, Nikolaos E; Tsiavos, Theodoros; Kotzabasis, Kiriakos

    2012-01-01

    In the present work, we tested the mode of interaction of all three polyamines (putrescine, spermidine and spermine) with chlorophyll a and b, as well as pheophytin a and b. The results showed that all three polyamines bind to the Mg ion of chlorophyll ring as probed by Raman spectroscopy. The coordination of spermine with Chl b has the most interesting features from all pigments tested. Spermine induces reversible increases and decreases of the fluorescence yield of Chl b at about 661 nm. Interestingly, equilibrium between a high-fluorescence yield conformation and a low yield is feasible by the interaction of chlorophyll b and aminic ligands. Furthermore, absorption data for the diagnostic regions of 518 and 535 nm are provided for all combinations of pigments and ligands. The significance and consistence of these results with respect to photochemical and bioenergetic principles are discussed.

  9. Lutein from Deepoxidation of Lutein Epoxide Replaces Zeaxanthin to Sustain an Enhanced Capacity for Nonphotochemical Chlorophyll Fluorescence Quenching in Avocado Shade Leaves in the Dark1

    Science.gov (United States)

    Förster, Britta; Pogson, Barry James; Osmond, Charles Barry

    2011-01-01

    Leaves of avocado (Persea americana) that develop and persist in deep shade canopies have very low rates of photosynthesis but contain high concentrations of lutein epoxide (Lx) that are partially deepoxidized to lutein (L) after 1 h of exposure to 120 to 350 μmol photons m−2 s−1, increasing the total L pool by 5% to 10% (ΔL). Deepoxidation of Lx to L was near stoichiometric and similar in kinetics to deepoxidation of violaxanthin (V) to antheraxanthin (A) and zeaxanthin (Z). Although the V pool was restored by epoxidation of A and Z overnight, the Lx pool was not. Depending on leaf age and pretreatment, the pool of ΔL persisted for up to 72 h in the dark. Metabolism of ΔL did not involve epoxidation to Lx. These contrasting kinetics enabled us to differentiate three states of the capacity for nonphotochemical chlorophyll fluorescence quenching (NPQ) in attached and detached leaves: ΔpH dependent (NPQΔpH) before deepoxidation; after deepoxidation in the presence of ΔL, A, and Z (NPQΔLAZ); and after epoxidation of A+Z but with residual ΔL (NPQΔL). The capacity of both NPQΔLAZ and NPQΔL was similar and 45% larger than NPQΔpH, but dark relaxation of NPQΔLAZ was slower. The enhanced capacity for NPQ was lost after metabolism of ΔL. The near equivalence of NPQΔLAZ and NPQΔL provides compelling evidence that the small dynamic pool ΔL replaces A+Z in avocado to “lock in” enhanced NPQ. The results are discussed in relation to data obtained with other Lx-rich species and in mutants of Arabidopsis (Arabidopsis thaliana) with increased L pools. PMID:21427278

  10. Nonphotochemical quenching of excitation energy in photosystem II. A picosecond time-resolved study of the low yield of chlorophyll a fluorescence induced by single-turnover flash in isolated spinach thylakoids.

    Science.gov (United States)

    Vasil'ev, S; Bruce, D

    1998-08-04

    Chlorophyll a fluorescence emission is widely used as a noninvasive measure of a number of parameters related to photosynthetic efficiency in oxygenic photosynthetic organisms. The most important component for the estimation of photochemistry is the relative increase in fluorescence yield between dark-adapted samples which have a maximal capacity for photochemistry and a minimal fluorescence yield (F0) and light-saturated samples where photochemistry is saturated and fluorescence yield is maximal (Fm). However, when photosynthesis is saturated with a short (less than 50 micro(s)) flash of light, which induces only one photochemical turnover of photosystem II, the maximal fluorescence yield is significantly lower (Fsat) than when saturation is achieved with a millisecond duration multiturnover flash (Fm). To investigate the origins of the difference in fluorescence yield between these two conditions, our time-resolved fluorescence apparatus was modified to allow collection of picosecond time-resolved decay kinetics over a short time window immediately following a saturating single-turnover flash (Fsat) as well as after a multiturnover saturating pulse (Fm). Our data were analyzed with a global kinetic model based on an exciton radical pair equilibrium model for photosystem II. The difference between Fm and Fsat was modeled well by changing only the rate constant for quenching of excitation energy in the antenna of photosystem II. An antenna-based origin for the quenching was verified experimentally by the observation that addition of the antenna quencher 5-hydroxy-1,4-naphthoquinone to thylakoids under Fm conditions resulted in decay kinetics and modeled kinetic parameters very similar to those observed under Fsat conditions in the absence of added quinone. Our data strongly support the origin of low fluorescence yield at Fsat to be an antenna-based nonphotochemical quenching of excitation energy in photosystem II which has not usually been considered explicitly in

  11. APPLICATION OF MODULATED CHLOROPHYLL FLUORESCENCE AND MODULATED CHLOROPHYLL FLUORESCENCE IMAGING IN STUDYING ENVIRONMENTAL STRESSES EFFECT

    Directory of Open Access Journals (Sweden)

    L. Guidi

    2016-03-01

    Full Text Available Chlorophyll (Chl a fluorescence is a widely used tool to monitor the photosynthetic process in plants subjected to environmental stresses.this review reports the theoretical bases of Chl fluorescence, and the significance of the most important Chl fluorescence parameters. it also reportshow these parameters can be utilised to estimate changes in photosystem ii (PSII photochemistry, linear electron flux and energy dissipationmechanisms. the relation between actual PSII photochemistry and CO2 assimilation is discussed, as is the role of photochemical andnon-photochemical quenching in inducing changes in PSII activity. the application of Chl fluorescence imaging to study heterogeneity on leaflamina is also considered. this review summarises only some of the results obtained by this methodology to study the effects of differentenvironmental stresses, namely water and nutrients availability, pollutants, temperature and salinity.

  12. An optimised method for correcting quenched fluorescence yield

    Directory of Open Access Journals (Sweden)

    L. Biermann

    2014-05-01

    Full Text Available Under high light intensity, phytoplankton protect their photosystems from bleaching through non-photochemical quenching processes. The consequence of this is suppression of fluorescence emission, which must be corrected when measuring in situ yield with fluorometers. Previously, this has been done using the limit of the mixed layer, assuming that phytoplankton are uniformly mixed from the surface to this depth. However, the assumption of homogeneity is not robust in oceanic regimes that support deep chlorophyll maxima. To account for these features, we correct from the limit of the euphotic zone, defined as the depth at which light is at ~1% of the surface value. This method was applied to fluorescence data collected by eleven animal-borne fluorometers deployed in the Southern Ocean over four austral summers. Six tags returned data showing evidence of deep chlorophyll features. Using the depth of the euphotic layer, quenching was corrected without masking subsurface fluorescence signals.

  13. Modelling chlorophyll fluorescence of kiwi fruit (Actinidia deliciosa).

    Science.gov (United States)

    Novo, Johanna Mendes; Iriel, Analia; Lagorio, M Gabriela

    2012-04-01

    Kiwi fruit displays chlorophyll fluorescence. A physical model was developed to reproduce the observed original fluorescence for the whole fruit, from the emission of the different parts of the kiwi fruit. The spectral distribution of fluorescence in each part of the fruit, was corrected to eliminate distortions due to light re-absorption and it was analyzed in relation to photosystem II-photosystem I ratio. Kiwi fruit also displays variable chlorophyll-fluorescence, similar to that observed from leaves. The maximum quantum efficiency of photosystem II photochemistry (F(v)/F(m)), the quantum efficiency of photosystem II (Φ(PSII)), and the photochemical and non-photochemical quenching coefficients (q(P) and q(NP) respectively) were determined and discussed in terms of the model developed. The study was extended by determining the photosynthetic parameters as a function of the storage time, at both 4 °C and room temperature for 25 days.

  14. Analysis of initial chlorophyll fluorescence induction kinetics in chloroplasts in terms of rate constants of donor side quenching release and electron trapping in photosystem II

    NARCIS (Netherlands)

    Vredenberg, W.J.

    2008-01-01

    The fluorescence induction F(t) of dark-adapted chloroplasts has been studied in multi-turnover 1 s light flashes (MTFs). A theoretical expression for the initial fluorescence rise is derived from a set of rate equations that describes the sequence of transfer steps associated with the reduction of

  15. Kinetic models of photosystem II should accommodate the effect of donor side quenching on variable chlorophyll a fluorescence in the microseconds time

    NARCIS (Netherlands)

    Vredenberg, W.J.

    2009-01-01

    Quantitative data on laser flash-induced variable fluorescence in the 100 ns to 1 ms time range (Belyaeva et al. in Photosynth Res 98:105–119, 2008) confirming those of others (Steffen et al. in Biochemistry 40:173–180, 2001, Biochemistry 44:3123–3132, 2005; Belyaeva et al. in Biophysics 51(6):976–9

  16. Effects of light quality on CO2 assimilation, chlorophyll-fluorescence quenching, expression of Calvin cycle genes and carbohydrate accumulation in Cucumis sativus.

    Science.gov (United States)

    Wang, Hong; Gu, Min; Cui, Jinxia; Shi, Kai; Zhou, Yanhong; Yu, Jingquan

    2009-07-17

    Light quality is thought to affect many plant physiological processes during growth and development, particularly photosynthesis. We examined how light quality influences plant photosynthesis by analyzing changes in photosynthetic parameters and expression levels of some photosynthesis related genes of cucumber (Cucumis sativus L. cv. Jinyou No. 1) plants. The plants were grown under different light qualities: purple (P), blue (B), green (G), yellow (Y), red (R) and white light (W) of the same photosynthetic photon flux density (PFD) about 350 micromol m(-2)s(-1) for 5 days. The results show that all plants grown under monochromatic light had reduced growth, CO(2) assimilation rate (Pn) and quantum yield of PSII electron transport (Phi(PSII)) as compared with plants grown under W, and these reductions were more significant in the plants under G, Y and R. The decrease in Phi(PSII) is mostly due to the reduction in photochemical quenching (qP). Interestingly, P- and B-grown plants had higher stomatal conductance (Gs), total and initial Rubisco activities and higher transcriptional levels of 10 genes which encode key enzymes in the Calvin cycle together with higher total soluble sugars, sucrose and starch contents as compared with W-grown plants, whereas in G-, Y-, and R-grown plants these parameters declined. Therefore, the reduction in Pn under P and B is likely the result of inactivation of photosystems, whilst under Y, G and R it is caused by, in addition to photosystem inactivation, the closure of stomata and the transcriptional down-regulation of genes for the Calvin cycle enzymes such as rbc L and rca. In conclusion, light quality alters plant photosynthesis by the effects on the activity of photosynthetic apparatus in leaves and the effects on the expression and/or activity of the Calvin cycle enzymes.

  17. Chlorophyll fluorescence imaging of cadmium-treated white cabbage plants

    Directory of Open Access Journals (Sweden)

    Borek M.

    2013-04-01

    Full Text Available The chlorophyll fluorescence imaging technique is a valuable tool to study the impact of heavy metal stress in plants. The aim of this paper was to investigate the influence of Cd on photosynthetic apparatus of white cabbage (Brassica oleracea subsp. capitata f. alba plants. Two cabbage cultivars ‘Ditmarska Najwcześniejsza’ (‘DN’; early and ‘Amager Polana’ (‘AP’; late were used. Cd was applied before planting seedlings (10 mg Cd kg−1 DM of soil.. Measurements were performed at the 3rd leaf after 2 weeks of planting. The level of Cd-induced stress to plants was estimated by chlorophyll (Chl content (photometrically and analyses of images and numeric values of the major fluorescence parameters of Chl (Chl fluorescence imaging system FluorCam. Cd negatively affected the chlorophyll content and Fv/Fm, Fv’/Fm’, Φ PSII and qP in leaves of early cultivar of white cabbage. However, in the case of late cv. we did not observe such distinct changes. It suggests that late cultivars. are more resistant to Cd than the early ones. Considering methodological aspect of the study, Chl fluorescence imaging can better reveal some alterations within the leaf, because numeric values of specific parameters, which are the averaged data collected from the whole leaf, cannot reflect the tissue specificity. Abbreviations: HM – heavy metal, Cd – cadmium, Chl – chlorophyll, Fv/Fm – photochemical efficiency of PSII in the dark-adapted state, F‘v’/F‘m’ – PSII maximum efficiency, Φ PSII – quantum efficiency of PSII electron transport, NPQ – nonphotochemical quenching of maximal Chl fluorescence, qP – photochemical quenching coefficient.

  18. Non-Photochemical Fluorescence Quenching Across Scales: From Chloroplasts to Plants to Communities

    NARCIS (Netherlands)

    Murchie, E.H.; Harbinson, J.

    2014-01-01

    Non-photochemical quenching (NPQ) of chlorophyll fluorescence, as a measure of photoprotective thermal dissipation of excess excitation energy (from singlet state chlorophyll a), is usually studied at the molecular, organelle, and leaf scale over relatively short time periods, where it is most readi

  19. Effects of Water Stress on Photochemical Quenching and Non-photochemical Quenching of Chlorophyll a Fluorescence in Four Tree Seedlings%水分胁迫对4种苗木叶绿素荧光的光化学淬灭和非光化学淬灭的影响

    Institute of Scientific and Technical Information of China (English)

    史胜青; 袁玉欣; 杨敏生; 梁海永; 张金香

    2004-01-01

    The changes of photochemical quenching(qp) and non-photochemical quenching(qN) of chlorophyll a fluorescence in leaves of four tree seedlings ( Gleditsia sinensis, Juglans regia, Diospyros kaki and Diospyros lotus ) were different between two different water stress ways:detached drought treatment and potted drought treatment. After 4 hours dehydration by leaf detaching,the qp values had significant decrease except J. regia, only 6 hours later, the qp values compared with contrast decreased significantly in four tree seedlings(P>0.05), but the range of reduction( G.sinensis, J.regia and D.lotus) was just 2.5% to 6.4%. D.kaki, however,got to 31.3%. While the qN values increased significantly with conducting dehydration of the detached leaves. However, the qp values of four species showed no significant decrease when they were growing in pots under soil water stress(40%~60% RWC) for 30 days; and the qN values decreased obviously with a exception in J. regia, which was consistent with that of detached leaf treatment. The results suggested that some difference or changes in mechanism of excess light energy dissipation might perform in four seedlings by short-term and long-term water stress.

  20. Phytoplankton productivity quantified from chlorophyll fluorescence

    DEFF Research Database (Denmark)

    Hancke, Kasper; Dalsgaard, Tage; Sejr, Mikael Kristian

    Phytoplankton are the main food source for marine life, and accurate uantification of its productivity is essential for understanding how marine food webs function. As a novel non-invasive technology, chlorophyll fluorescence can be used to assess in situ primary production in phytoplankton...

  1. Effect of Salinity on Chlorophyll Fluorescence and Chlorophyll Content of the Desert Shrub Calotropis procera

    OpenAIRE

    , A. Akhkha; , T. Boutraa

    2016-01-01

    The effect of salinity stress on the efficiency of the photosynthetic apparatus in the desert shrub Calotropis procera Aiton (family: Asclepiadaceae) was investigated using chlorophyll fluorescence technique. This technique allowed the determination of a number of chlorophyll fluorescence parameters such as initial fluorescence Fo, maximum fluorescence Fm and variable fluorescence Fv. Furthermore, the effect of salinity stress on other chlorophyll fluorescence parameters (Fv / Fo and Fv / Fm ...

  2. Chlorophyll a fluorescence analysis in forests

    OpenAIRE

    M. Pollastrini; Holland, V; Brüggemann, W.; F. Bussotti

    2016-01-01

    A European-wide assessment of chlorophyll a fluorescence (ChlF, prompt fluorescence on dark-adapted samples) parameters in forest ecosystems was carried out in the years 2012-2013, within the 7FP FunDivEUROPE project. A total of 1596 trees growing in 209 stands distributed in six countries, from Mediterranean to boreal sites, were sampled. This paper shows the applicability of the ChlF in forest ecology surveys, the protocols adopted for leaf sampling and ChlF measurements, the variability of...

  3. CHLOROPHYLL a FLUORESCENCE ANALYSIS IN FORESTS

    OpenAIRE

    M. Pollastrini; Holland, V; Brüggemann, W.; F. Bussotti

    2016-01-01

    A European-wide assessment of chlorophyll a fluorescence (ChlF, prompt fluorescence on dark-adapted samples) parameters in forest ecosystems was carried out in the years 2012-2013, within the 7FP FunDivEUROPE project. A total of 1596 trees growing in 209 stands distributed in six countries, from Mediterranean to boreal sites, were sampled. This paper shows the applicability of the ChlF in forest ecology surveys, the protocols adopted for leaf sampling and ChlF measurements, the variability of...

  4. Salt stress change chlorophyll fluorescence in mango

    Directory of Open Access Journals (Sweden)

    Cicero Cartaxo de Lucena

    2012-12-01

    Full Text Available This study evaluated the tolerance of mango cultivars 'Haden', 'Palmer', 'Tommy Atkins' and 'Uba' grafted on rootstock 'Imbú' to salt stress using chlorophyll fluorescence. Plants were grown in modified Hoagland solution containing 0, 15, 30, and 45 mmol L-1 NaCl. At 97 days the parameters of the chlorophyll fluorescence (F0, Fm, Fv, F0/Fm, Fv/Fm, Fv'/Fm', ΦPSII = [(Fm'-Fs/(Fm'], D = (1- Fv'/Fm' and ETR = (ΦPSII×PPF×0,84×0,5 were determined. At 100 days, the leaf emission and leaf area, toxicity and leaf abscission indexes were determined. In all cultivars evaluated, in different degree, there were decreases in photochemical efficiency of photosystem II, enhanced concentrations from 15 mmol L-1 NaCl. The decreases in the potential quantum yield of photosystem II (Fv/Fm were 27.9, 18.7, 20.5, and 27.4%, for cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba', respectively, when grown in 45 mmol L-1 NaCl. It was found decreases in leaf emission and mean leaf area in all cultivars from 15 mmol L-1 NaCl. There were increases in leaf toxicity of 33.0, 67.5, 41.6 and 80.8% and in leaf abscission of 71.8, 29.2, 32.5, and 67.9% for the cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba' respectively, when grown in 45 mmol L-1 NaCl. Leaf toxicity and leaf abscission were not observed in 15 mmol L-1 NaCl. The decrease in Fv/Fm ratio were accompanied by decreasing in leaf emission and increased leaf toxicity index, showing, therefore, the potential of chlorophyll fluorescence in the early detection of salt stress in mango tree.

  5. Fluorescence quenching of TMR by guanosine in oligonucleotides

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Nucleotide-specific fluorescence quenching in fluorescently labeled DNA has many applications in biotechnology. We have studied the inter-and intra-molecular quenching of tetramethylrhodamine (TMR) by nucleotides to better understand their quenching mechanism and influencing factors. In agreement with previous work, dGMP can effectively quench TMR, while the quenching of TMR by other nucleotides is negligible. The Stern-Volmer plot between TMR and dGMP delivers a bimolecular quenching constant of Ks=52.3 M-1. The fluorescence of TMR in labeled oligonucleotides decreases efficiently through photoinduced electron transfer by guanosine. The quenching rate constant between TMR and guanosine was measured using fluorescence correlation spectroscopy (FCS). In addition, our data show that the steric hindrance by bases around guanosine has significant effect on the G-quenching. The availability of these data should be useful in designing fluorescent oligonucleotides and understanding the G-quenching process.

  6. Modeling chlorophyll a fluorescence transient: relation to photosynthesis.

    Science.gov (United States)

    Stirbet, A; Riznichenko, G Yu; Rubin, A B; Govindjee

    2014-04-01

    To honor Academician Alexander Abramovitch Krasnovsky, we present here an educational review on the relation of chlorophyll a fluorescence transient to various processes in photosynthesis. The initial event in oxygenic photosynthesis is light absorption by chlorophylls (Chls), carotenoids, and, in some cases, phycobilins; these pigments form the antenna. Most of the energy is transferred to reaction centers where it is used for charge separation. The small part of energy that is not used in photochemistry is dissipated as heat or re-emitted as fluorescence. When a photosynthetic sample is transferred from dark to light, Chl a fluorescence (ChlF) intensity shows characteristic changes in time called fluorescence transient, the OJIPSMT transient, where O (the origin) is for the first measured minimum fluorescence level; J and I for intermediate inflections; P for peak; S for semi-steady state level; M for maximum; and T for terminal steady state level. This transient is a real signature of photosynthesis, since diverse events can be related to it, such as: changes in redox states of components of the linear electron transport flow, involvement of alternative electron routes, the build-up of a transmembrane pH gradient and membrane potential, activation of different nonphotochemical quenching processes, activation of the Calvin-Benson cycle, and other processes. In this review, we present our views on how different segments of the OJIPSMT transient are influenced by various photosynthetic processes, and discuss a number of studies involving mathematical modeling and simulation of the ChlF transient. A special emphasis is given to the slower PSMT phase, for which many studies have been recently published, but they are less known than on the faster OJIP phase.

  7. Reductive fluorescence quenching of DMP with aniline

    Energy Technology Data Exchange (ETDEWEB)

    Asha Jhonsi, M. [B.S. Abdur Rahman University, Vandalur, Chennai 600048, Tamil Nadu (India); Kathiravan, A., E-mail: akathir23@hotmail.com [National Centre for Ultrafast Processes, University of Madras, Taramani Campus, Chennai 600113, Tamil Nadu (India)

    2014-01-15

    The photoinduced electron transfer (PET) between 8-(4-methoxyphenyl)-3,5-di[(E)-1-(4-methoxyphenyl)methylidene]-1,2,3,5,6, 7-hexahydrodicyclopenta[b,e]pyridine (DMP) and aniline is studied in acetonitrile medium by using steady state and time resolved absorption and fluorescence spectroscopic methods. Bimolecular quenching rate constants (k{sub q}) were calculated from the obtained linear Stern–Volmer plots from both steady state and time resolved measurements. The rate constant (k{sub q}) for PET between DMP and aniline is 1.4×10{sup 10} M{sup −1} s{sup −1}, which is in diffusion control limit. The free energy change (ΔG{sup 0}) has been evaluated by using Rehm–Weller equation for the evidence of electron transfer from aniline to DMP. Direct evidence for the electron transfer reaction in the present system has been obtained by characterizing the aniline cation radical using nanosecond time resolved absorption measurements in the visible region. Further, this quenching mechanism is attributed to be reductive in nature i.e. electron transfer occurs from ground state aniline to excited DMP. This is the first example of reductive fluorescence quenching of DMP with aniline in acetonitrile ever known. -- Highlights: • Photoinduced electron transfer between DMP and aniline using time resolved absorption and fluorescence spectroscopy has been investigated. • Reductive quenching behavior was observed. • Direct evidence for the ET reaction in the present system has been obtained by characterizing the aniline cation radical.

  8. A model for chlorophyll fluorescence and photosynthesis at leaf scale

    NARCIS (Netherlands)

    Tol, van der C.; Verhoef, W.; Rosema, A.

    2009-01-01

    This paper presents a leaf biochemical model for steady-state chlorophyll fluorescence and photosynthesis of C3 and C4 vegetation. The model is a tool to study the relationship between passively measured steady-state chlorophyll fluorescence and actual photosynthesis, and its evolution during the da

  9. A model for chlorophyll fluorescence and photosynthesis at leaf scale

    NARCIS (Netherlands)

    Tol, van der C.; Verhoef, W.; Rosema, A.

    2009-01-01

    This paper presents a leaf biochemical model for steady-state chlorophyll fluorescence and photosynthesis of C3 and C4 vegetation. The model is a tool to study the relationship between passively measured steady-state chlorophyll fluorescence and actual photosynthesis, and its evolution during the

  10. Modulated Chlorophyll "a" Fluorescence: A Tool for Teaching Photosynthesis

    Science.gov (United States)

    Marques da Silva, Jorge; Bernardes da Silva, Anabela; Padua, Mario

    2007-01-01

    "In vivo" chlorophyll "a" fluorescence is a key technique in photosynthesis research. The recent release of a low cost, commercial, modulated fluorometer enables this powerful technology to be used in education. Modulated chlorophyll a fluorescence measurement "in vivo" is here proposed as a tool to demonstrate basic…

  11. Modulated Chlorophyll "a" Fluorescence: A Tool for Teaching Photosynthesis

    Science.gov (United States)

    Marques da Silva, Jorge; Bernardes da Silva, Anabela; Padua, Mario

    2007-01-01

    "In vivo" chlorophyll "a" fluorescence is a key technique in photosynthesis research. The recent release of a low cost, commercial, modulated fluorometer enables this powerful technology to be used in education. Modulated chlorophyll a fluorescence measurement "in vivo" is here proposed as a tool to demonstrate basic photosynthesis phenomena to…

  12. Quenching of fluorescence in membrane protein by hypocrellin B.

    Science.gov (United States)

    Yue, J; Pang, S

    1997-04-01

    The hypocrellin B (HB) was used as a fluorescence quencher to study the basic physical charactcristics of HB in membrane systems, including the diffusion speed of quencher from aqueous phase into membrane phase, the partition coefficient (P) of quenchtr between membrane and water, and the fluorescence quenching constant of protein (K(sv); K(q),). The experimental results show that the quenching of fluorescence in membrane protein by HB can be determined by the principle of dynamic quenching. The experimental process of fluorescence quenching was observed in detail by using the ESR technique. The signal of HB- was found to arise from an electron transfer from excited trytophan to HB.

  13. Quenching of fluorescence in membrane protein by hypocrellin B

    Institute of Scientific and Technical Information of China (English)

    乐加昌; 庞素珍

    1997-01-01

    The hypocrellin B (HB) was used as a fluorescence quencher to study the basic physical characteris-tics of HB in membrane systems, including the diffusion speed of quencher from aqueous phase into membrane phase, the partition coefficient (P) of quencher between membrane and water, and the fluorescence quenching constant of protein (Ksv; Kq). The experimental results show that the quenching of fluorescence in membrane protein by HB can be determined by the principle of dynamic quenching. The experimental process of fluorescence quenching was ob-served in detail by using the ESR technique. The signal of HB" was found to arise from an electron transfer from ex-cited trytophan to HB.

  14. Tomato seeds maturity detection system based on chlorophyll fluorescence

    Science.gov (United States)

    Li, Cuiling; Wang, Xiu; Meng, Zhijun

    2016-10-01

    Chlorophyll fluorescence intensity can be used as seed maturity and quality evaluation indicator. Chlorophyll fluorescence intensity of seed coats is tested to judge the level of chlorophyll content in seeds, and further to judge the maturity and quality of seeds. This research developed a detection system of tomato seeds maturity based on chlorophyll fluorescence spectrum technology, the system included an excitation light source unit, a fluorescent signal acquisition unit and a data processing unit. The excitation light source unit consisted of two high power LEDs, two radiators and two constant current power supplies, and it was designed to excite chlorophyll fluorescence of tomato seeds. The fluorescent signal acquisition unit was made up of a fluorescence spectrometer, an optical fiber, an optical fiber scaffolds and a narrowband filter. The data processing unit mainly included a computer. Tomato fruits of green ripe stage, discoloration stage, firm ripe stage and full ripe stage were harvested, and their seeds were collected directly. In this research, the developed tomato seeds maturity testing system was used to collect fluorescence spectrums of tomato seeds of different maturities. Principal component analysis (PCA) method was utilized to reduce the dimension of spectral data and extract principal components, and PCA was combined with linear discriminant analysis (LDA) to establish discriminant model of tomato seeds maturity, the discriminant accuracy was greater than 90%. Research results show that using chlorophyll fluorescence spectrum technology is feasible for seeds maturity detection, and the developed tomato seeds maturity testing system has high detection accuracy.

  15. Thermal quenching of fluorescence in condensed media

    Science.gov (United States)

    Lagos, Miguel; Paredes, Rodrigo

    2016-09-01

    Environmental factors strongly affect the features of the electromagnetic spectra of fluorescent compounds hosted by material media. The shape of the absorption and emission peaks, their characteristic asymmetry and breadth, the Stokes shift and quantum yield are generally temperature dependent and heavily influenced by both the local and extended physical properties of the medium. The theoretical method used before to obtain the lineshape function is extended here to other terms of the interaction energy between the optically sensitive orbital and the hosting medium, which become significant when the spectral feature is broad. An analytical expression for the temperature dependent decay rate by non-radiative processes is obtained by this way. Comparison with experiment on thermal quenching gives agreement within the experimental uncertainty. The solvent polarity, its protic or aprotic character, hydrogen bonds, proximity effects and presence of quenchers are expected to enter through the coupling constants of the corresponding energy terms.

  16. Chlorophyll a fluorescence and herbicide efficacy, metabolism and selectivity

    DEFF Research Database (Denmark)

    Abbas Poor, Majid

    Analysis of chlorophyll fluorescence induction curve (Kautsky curve) parameters was used for the study of the efficacy, metabolism and selectivity of ACCase, PSII and EPSPS inhibitors. Fv/Fm, Fvj and area above Kautsky curve and maximum fluorescence were selected among numerous fluorescence...

  17. An overview of remote sensing of chlorophyll fluorescence

    Science.gov (United States)

    Xing, Xiao-Gang; Zhao, Dong-Zhi; Liu, Yu-Guang; Yang, Jian-Hong; Xiu, Peng; Wang, Lin

    2007-03-01

    Besides empirical algorithms with the blue-green ratio, the algorithms based on fluorescence are also important and valid methods for retrieving chlorophyll-a concentration in the ocean waters, especially for Case II waters and the sea with algal blooming. This study reviews the history of initial cognitions, investigations and detailed approaches towards chlorophyll fluorescence, and then introduces the biological mechanism of fluorescence remote sensing and main spectral characteristics such as the positive correlation between fluorescence and chlorophyll concentration, the red shift phenomena. Meanwhile, there exist many influence factors that increase complexity of fluorescence remote sensing, such as fluorescence quantum yield, physiological status of various algae, substances with related optical property in the ocean, atmospheric absorption etc. Based on these cognitions, scientists have found two ways to calculate the amount of fluorescence detected by ocean color sensors: fluorescence line height and reflectance ratio. These two ways are currently the foundation for retrieval of chlorophyl l - a concentration in the ocean. As the in-situ measurements and synchronous satellite data are continuously being accumulated, the fluorescence remote sensing of chlorophyll-a concentration in Case II waters should be recognized more thoroughly and new algorithms could be expected.

  18. CHLOROPHYLL a FLUORESCENCE ANALYSIS IN FORESTS

    Directory of Open Access Journals (Sweden)

    M. Pollastrini

    2016-03-01

    Full Text Available A European-wide assessment of chlorophyll a fluorescence (ChlF, prompt fluorescence on dark-adapted samples parameters in forest ecosystems was carried out in the years 2012-2013, within the 7FP FunDivEUROPE project. A total of 1596 trees growing in 209 stands distributed in six countries, from Mediterranean to boreal sites, were sampled. This paper shows the applicability of the ChlF in forest ecology surveys, the protocols adopted for leaf sampling and ChlF measurements, the variability of the ChlF parameters within and between trees, their dependence to environmental factors and the relationships with other functional leaf traits. The most relevant findings were as follows: (i The least variable ChlF parameter within and between the trees was the maximum quantum yield of primary photochemistry (FV/FM, whereas the performance indices (PIABS and PITOT showed the highest variability; (ii for a given tree, the ChlF parameters measured at two heights of the crown (top and bottom leaves were correlated and, in coniferous species, the ChlF parameters were correlated between different needle age classes (from the current year and previous year; (iii the ChlF parameters showed a geographical pattern, and the photochemical performance of the forest trees was higher in central Europe than in the edge sites (northernmost and southernmost; and (iv ChlF parameters showed different sensitivity to specific environmental factors: FV/FM increased with the increase of the leaf area index of stands and soil fertility; ΔVIP was reduced under high temperature and drought. The photochemical responses of forest tree species, analyzed with ChlF parameters, were influenced by the ecology of the trees (i.e. their functional groups, continental distribution, successional status, etc., tree species’ richness and composition of the stands. Our results support the applicability and usefulness of the ChlF in forest monitoring investigations on a large spatial scale and

  19. Non-photochemical quenching in cryptophyte alga Rhodomonas salina is located in chlorophyll a/c antennae.

    Science.gov (United States)

    Kaňa, Radek; Kotabová, Eva; Sobotka, Roman; Prášil, Ondřej

    2012-01-01

    Photosynthesis uses light as a source of energy but its excess can result in production of harmful oxygen radicals. To avoid any resulting damage, phototrophic organisms can employ a process known as non-photochemical quenching (NPQ), where excess light energy is safely dissipated as heat. The mechanism(s) of NPQ vary among different phototrophs. Here, we describe a new type of NPQ in the organism Rhodomonas salina, an alga belonging to the cryptophytes, part of the chromalveolate supergroup. Cryptophytes are exceptional among photosynthetic chromalveolates as they use both chlorophyll a/c proteins and phycobiliproteins for light harvesting. All our data demonstrates that NPQ in cryptophytes differs significantly from other chromalveolates - e.g. diatoms and it is also unique in comparison to NPQ in green algae and in higher plants: (1) there is no light induced xanthophyll cycle; (2) NPQ resembles the fast and flexible energetic quenching (qE) of higher plants, including its fast recovery; (3) a direct antennae protonation is involved in NPQ, similar to that found in higher plants. Further, fluorescence spectroscopy and biochemical characterization of isolated photosynthetic complexes suggest that NPQ in R. salina occurs in the chlorophyll a/c antennae but not in phycobiliproteins. All these results demonstrate that NPQ in cryptophytes represents a novel class of effective and flexible non-photochemical quenching.

  20. Non-photochemical quenching in cryptophyte alga Rhodomonas salina is located in chlorophyll a/c antennae.

    Directory of Open Access Journals (Sweden)

    Radek Kaňa

    Full Text Available Photosynthesis uses light as a source of energy but its excess can result in production of harmful oxygen radicals. To avoid any resulting damage, phototrophic organisms can employ a process known as non-photochemical quenching (NPQ, where excess light energy is safely dissipated as heat. The mechanism(s of NPQ vary among different phototrophs. Here, we describe a new type of NPQ in the organism Rhodomonas salina, an alga belonging to the cryptophytes, part of the chromalveolate supergroup. Cryptophytes are exceptional among photosynthetic chromalveolates as they use both chlorophyll a/c proteins and phycobiliproteins for light harvesting. All our data demonstrates that NPQ in cryptophytes differs significantly from other chromalveolates - e.g. diatoms and it is also unique in comparison to NPQ in green algae and in higher plants: (1 there is no light induced xanthophyll cycle; (2 NPQ resembles the fast and flexible energetic quenching (qE of higher plants, including its fast recovery; (3 a direct antennae protonation is involved in NPQ, similar to that found in higher plants. Further, fluorescence spectroscopy and biochemical characterization of isolated photosynthetic complexes suggest that NPQ in R. salina occurs in the chlorophyll a/c antennae but not in phycobiliproteins. All these results demonstrate that NPQ in cryptophytes represents a novel class of effective and flexible non-photochemical quenching.

  1. Chlorophyll Fluorescence Imaging Uncovers Photosynthetic Fingerprint of Citrus Huanglongbing

    Directory of Open Access Journals (Sweden)

    Haiyan Cen

    2017-08-01

    Full Text Available Huanglongbing (HLB is one of the most destructive diseases of citrus, which has posed a serious threat to the global citrus production. This research was aimed to explore the use of chlorophyll fluorescence imaging combined with feature selection to characterize and detect the HLB disease. Chlorophyll fluorescence images of citrus leaf samples were measured by an in-house chlorophyll fluorescence imaging system. The commonly used chlorophyll fluorescence parameters provided the first screening of HLB disease. To further explore the photosynthetic fingerprint of HLB infected leaves, three feature selection methods combined with the supervised classifiers were employed to identify the unique fluorescence signature of HLB and perform the three-class classification (i.e., healthy, HLB infected, and nutrient deficient leaves. Unlike the commonly used fluorescence parameters, this novel data-driven approach by using the combination of the mean fluorescence parameters and image features gave the best classification performance with the accuracy of 97%, and presented a better interpretation for the spatial heterogeneity of photochemical and non-photochemical components in HLB infected citrus leaves. These results imply the potential of the proposed approach for the citrus HLB disease diagnosis, and also provide a valuable insight for the photosynthetic response to the HLB disease.

  2. Chlorophyll Fluorescence Imaging Uncovers Photosynthetic Fingerprint of Citrus Huanglongbing.

    Science.gov (United States)

    Cen, Haiyan; Weng, Haiyong; Yao, Jieni; He, Mubin; Lv, Jingwen; Hua, Shijia; Li, Hongye; He, Yong

    2017-01-01

    Huanglongbing (HLB) is one of the most destructive diseases of citrus, which has posed a serious threat to the global citrus production. This research was aimed to explore the use of chlorophyll fluorescence imaging combined with feature selection to characterize and detect the HLB disease. Chlorophyll fluorescence images of citrus leaf samples were measured by an in-house chlorophyll fluorescence imaging system. The commonly used chlorophyll fluorescence parameters provided the first screening of HLB disease. To further explore the photosynthetic fingerprint of HLB infected leaves, three feature selection methods combined with the supervised classifiers were employed to identify the unique fluorescence signature of HLB and perform the three-class classification (i.e., healthy, HLB infected, and nutrient deficient leaves). Unlike the commonly used fluorescence parameters, this novel data-driven approach by using the combination of the mean fluorescence parameters and image features gave the best classification performance with the accuracy of 97%, and presented a better interpretation for the spatial heterogeneity of photochemical and non-photochemical components in HLB infected citrus leaves. These results imply the potential of the proposed approach for the citrus HLB disease diagnosis, and also provide a valuable insight for the photosynthetic response to the HLB disease.

  3. Anthracene Fluorescence Quenching by a Tetrakis (Ketocarboxamide Cavitand

    Directory of Open Access Journals (Sweden)

    Tibor Zoltan Janosi

    2014-01-01

    Full Text Available Quenching of both fluorescence lifetime and fluorescence intensity of anthracene was investigated in the presence of a newly derived tetrakis (ketocarboxamide cavitand at various concentrations. Time-correlated single photon counting method was applied for the lifetime measurements. A clear correlation between the fluorescence lifetime of anthracene as a function of cavitand concentration in dimethylformamide solution was observed. The bimolecular collisional quenching constant was derived from the decrease of lifetime. Fluorescence intensity was measured in the emission wavelength region around 400 nm as a result of excitation at 280 nm. Effective quenching was observed in the presence of the cavitand. The obtained Stern-Volmer plot displayed upward curvature. The results did not follow even extended Stern-Volmer behavior, often used to describe deviations from static bimolecular quenching. To explain our results we adopted the Smoluchowski model and obtained a reasonable estimate for the molecular radius of the cavitand in solution.

  4. Time-resolved spectroscopy of the fluorescence quenching of a donor — acceptor pair by halothane

    Science.gov (United States)

    Sharma, A.; Draxler, S.; Lippitsch, M. E.

    1992-04-01

    Donor (anthracene) sensitized acceptor (perylene) fluorescence is quenched more efficiently by halothane than is intrinsic perylene fluorescence. The underlying process of dynamic fluorescence quenching is investigated by time-resolved fluorescence spectroscopy.

  5. Chlorophyll a fluorescence to phenotype wheat genotypes for heat tolerance

    DEFF Research Database (Denmark)

    Sharma, Dew Kumari; Andersen, Sven Bode; Ottosen, Carl-Otto

    . Chlorophyll a fluorescence has been a versatile tool in photosynthesis research to measure plant responses to various abiotic stresses that affect PSII. We aim to establish a reproducible protocol to measure response of wheat genotypes to high temperature, based on the physiological marker, maximum quantum......%. Our protocol seems to be stable over environments since interaction between genotypes and the three repeated experiments separated in time was not statistically significant. The chlorophyll a fluorescence protocol may enable identification of wheat lines reliably more or less tolerant to heat stress...

  6. Plasmonic Molecular Nanohybrids—Spectral Dependence of Fluorescence Quenching

    Directory of Open Access Journals (Sweden)

    Maria Olejnik

    2012-01-01

    Full Text Available We demonstrate strong spectral dependence of the efficiency of fluorescence quenching in molecular systems composed of organic dyes and gold nanoparticles. In order to probe the coupling with metallic nanoparticles we use dyes with varied spectral overlap between the plasmon resonance and their absorption. Hybrid molecular structures were obtained via conjugation of metallic nanoparticles with the dyes using biotin-streptavidin linkage. For dyes featuring absorption above the plasmon excitation in gold nanoparticles, laser excitation induces minute changes in the fluorescence intensity and its lifetime for both conjugated and non-conjugated mixtures, which are the reference. In contrast, when the absorption of the dye overlaps with the plasmon resonance, the effect is quite dramatic, reaching 85% and 95% fluorescence quenching for non-conjugated and conjugated mixtures, respectively. The degree of fluorescence quenching strongly depends upon the concentration of metallic nanoparticles. Importantly, the origin of the fluorescence quenching is different in the case of the conjugated mixture, as evidenced by time-resolved fluorescence. For conjugated mixtures of dyes resonant with plasmon, excitation features two-exponential decay. This is in contrast to the single exponential decay measured for the off-resonant configuration. The results provide valuable insight into spectral dependence of the fluorescence quenching in molecular assemblies involving organic dyes and metallic nanoparticles.

  7. Measurement of cell volume changes by fluorescence self-quenching

    DEFF Research Database (Denmark)

    Hamann, Steffen; Kiilgaard, J.F.; Litman, Thomas

    2002-01-01

    At high concentrations, certain fluorophores undergo self-quenching, i.e., fluorescence intensity decreases with increasing fluorophore concentration. Accordingly, the self-quenching properties can be used for measuring water volume changes in lipid vesicles. In cells, quantitative determination...... of water transport using fluorescence self-quenching has been complicated by the requirement of relatively high (mM) and often toxic loading concentrations. Here we report a simple method that uses low (muM) loading concentrations of calcein-acetoxymethyl ester (calcein-AM) to obtain intracellular...... concentrations of the fluorophore calcein suitable for measurement of changes in cell water volume by self-quenching. The relationship between calcein fluorescence intensity, when excited at 490 nm (its excitation maximum), and calcein concentration was investigated in vitro and in various cultured cell types...

  8. Chlorophyll a fluorescence to phenotype wheat genotypes for heat tolerance

    DEFF Research Database (Denmark)

    Sharma, Dew Kumari; Andersen, Sven Bode; Ottosen, Carl-Otto

    In prospects of global climate change, heat stress is a rising constraint for the productivity of wheat (Triticum aestivum L.). It is a heat-susceptible crop beyond 17-23oC temperature throughout its phenological stages, flowering phase being the most sensitive stage. Chlorophyll a fluorescence...

  9. Polyamines induce aggregation of LHC II and quenching of fluorescence in vitro.

    Science.gov (United States)

    Tsiavos, Theodoros; Ioannidis, Nikolaos E; Kotzabasis, Kiriakos

    2012-05-01

    Dissipation of excess excitation energy within the light-harvesting complex of Photosystem II (LHC II) is a main process in plants, which is measured as the non-photochemical quenching of chlorophyll fluorescence or qE. We showed in previous works that polyamines stimulate qE in higher plants in vivo and in eukaryotic algae in vitro. In the present contribution we have tested whether polyamines can stimulate quenching in trimeric LHC II and monomeric light-harvesting complex b proteins from higher plants. The tetramine spermine was the most potent quencher and induced aggregation of LHC II trimers, due to its highly cationic character. Two transients are evident at 100 μM and 350 μM for the fluorescence and absorbance signals of LHC II respectively. On the basis of observations within this work, some links between polyamines and the activation of qE in vivo is discussed.

  10. Spectroscopic evidence of xanthine compounds fluorescence quenching effect on water-soluble porphyrins

    Science.gov (United States)

    Makarska-Bialokoz, Magdalena

    2015-02-01

    The formation of π-stacked complexes between water-soluble porphyrins: 4,4‧,4″,4″‧-(21H,23H-porphine-5,10,15,20-tetrayl)tetrakis-(benzoic acid) (H2TCPP), 5,10,15,20-tetrakis(4-sulfonatophenyl)-21H,23H-porphine (H2TPPS4), 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H2TTMePP), 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine tetra-p-tosylate (H2TMePyP), the Cu(II) complexes of H2TTMePP and H2TMePyP, as well as chlorophyll a with xanthine, theophylline (1,3-dimethylxanthine) and theobromine (3,7-dimethylxanthine) has been studied analysing their absorption and steady-state fluorescence spectra in aqueous (or acetone in case of chlorophyll a) solution. During titration by the compounds from xanthine group the bathochromic effect in the porphyrin absorption spectra as well as the hypochromicity of the porphyrin Soret maximum can be noticed. The fluorescence quenching effect observed during interactions in the systems examined suggests the process of static quenching. The association and fluorescence quenching constants are of the order of magnitude of 103 - 102 mol-1. The results obtained show that xanthine and its derivatives can quench the fluorescence of the porphyrins according to the number of methyl groups in the molecule of quencher.

  11. Monitoring the Photosynthetic Apparatus During Space Flight: Interspecific Variation in Chlorophyll Fluorescence Signatures Induced by Different Root Zone Stresses

    Science.gov (United States)

    Bubenheim, David L.; Patterson, Mark T.; Kliss, Mark H. (Technical Monitor)

    1996-01-01

    Chlorophyll fluorescence has been used extensively as a tool to indicate stress to the photosynthetic apparatus in green plants. A rise in fluorescence has been attributed to the blockage of photosystem II photochemistry, and patterns of fluorescence decay (quenching) from dark adapted leaves can be related to specific photochemical and non-photochemical deexcitation pathways of light trapped by the photosynthetic apparatus and thus result in characteristically different fluorescence signatures. Four distantly related plant species, Hypocharis radicata (Asteraceae), Brassica rapa (Brassicaceae), Spinacea oleracea (Chenopodiaceae) and Triticum aestivum (Poaceae), were grown hydroponically for three weeks before the initiation of three different root zone stresses (10 mM Cu, 100 mM NaCl and nitrogen deficient nutrition). After 10 days, characteristic fluorescence signatures for each stress could be noted although the degree varied between species. Fast kinetics analysis showed a reduction in plastoquinone pool size for copper and nitrogen stress for all species but a more species specific result with NaCl stress. Photochemical quenching kinetics varied between species and stress treatments from no quenching in S. oleracea in copper treatments to increased photochemical quenching in NaCl treatments. Non-photochemical quenching kinetics demonstrated a distinct pattern between stresses for all species. Copper treatments characteristically exhibited a shallow, flat non-photochemical quenching profile suggesting a general blockage of electron transport whereas NaCl treatments exhibited a slow rising profile that suggested damage to thylakoid acidification kinetics and nitrogen deficiency exhibited a fast rising and declining profile that suggested an altered state 1-state 2 transition regulated by the phosphorylation of LHCII. These results demonstrate characteristic fluorescence signatures for specific plant stresses that may be applied to different, unrelated plant

  12. Molecular environments of divinyl chlorophylls in Prochlorococcus and Synechocystis: differences in fluorescence properties with chlorophyll replacement.

    Science.gov (United States)

    Mimuro, Mamoru; Murakami, Akio; Tomo, Tatsuya; Tsuchiya, Tohru; Watabe, Kazuyuki; Yokono, Makio; Akimoto, Seiji

    2011-05-01

    A marine cyanobacterium, Prochlorococcus, is a unique oxygenic photosynthetic organism, which accumulates divinyl chlorophylls instead of the monovinyl chlorophylls. To investigate the molecular environment of pigments after pigment replacement but before optimization of the protein moiety in photosynthetic organisms, we compared the fluorescence properties of the divinyl Chl a-containing cyanobacteria, Prochlorococcus marinus (CCMP 1986, CCMP 2773 and CCMP 1375), by a Synechocystis sp. PCC 6803 (Synechocystis) mutant in which monovinyl Chl a was replaced with divinyl Chl a. P. marinus showed a single fluorescence band for photosystem (PS) II at 687nm at 77K; this was accompanied with change in pigment, because the Synechocystis mutant showed the identical shift. No fluorescence bands corresponding to the PS II 696-nm component and PS I longer-wavelength component were detected in P. marinus, although the presence of the former was suggested using time-resolved fluorescence spectra. Delayed fluorescence (DF) was detected at approximately 688nm with a lifetime of approximately 29ns. In striking contrast, the Synechocystis mutant showed three fluorescence bands at 687, 696, and 727nm, but suppressed DF. These differences in fluorescence behaviors might not only reflect differences in the molecular structure of pigments but also differences in molecular environments of pigments, including pigment-pigment and/or pigment-protein interactions, in the antenna and electron transfer systems.

  13. Fluorescence self-quenching of tetraphenylporphyrin in liquid medium

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Mihir [Integrated Science Education and Research Centre, Siksha-Bhavana, Visva-Bharati, Santiniketan 731235 (India); Nath, Sukhendu [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Hajra, Alakananda [Department of Chemistry, Siksha-Bhavana, Visva-Bharati, Santiniketan 731235 (India); Sinha, Subrata, E-mail: subratasinha67@rediffmail.com [Integrated Science Education and Research Centre, Siksha-Bhavana, Visva-Bharati, Santiniketan 731235 (India)

    2013-09-15

    Self-quenching of the fluorescence emission of tetraphenylporphyrin at high concentrations in toluene at the ambient temperature (300 K) is discussed in detail based on steady state and time-resolved fluorescence measurements. The fluorescence self-quenching is mainly attributed to re-absorption effect and the Förster type resonance energy transfer process (homotransfer). The re-absorption effect is found to deform the fluorescence emission spectra significantly in energy positions as well as relative intensities of different peaks at high concentrations. Nearly ideal fluorescence emission spectra are observed at a concentration ∼10{sup −7} mol/L. Moreover, there is an apparent enhancement of the fluorescence lifetime value of tetraphenylporphyrin in toluene at high concentrations, especially on the blue side of the fluorescence emission spectra. To the best knowledge of the authors, this is the first detail report on the fluorescence self-quenching of porphyrins in liquid medium. This finding carries great importance in view of the widespread research on porphyrins in the fields of solar light harvesting, artificial photosynthesis, photodynamic therapy, etc. -- Highlights: • The effect of concentration on the fluorescence emission spectra of tetraphenylporphyrin (TPhP) in toluene at 300 K is investigated by using steady state and time-resolved fluorescence techniques. • Both re-absorption effect and the Förster type resonance energy transfer are found to be responsible for the observed fluorescence self-quenching at high concentrations. • These investigations are extremely important in view of the extensive applications of porphyrins in the fabrication of molecular electronic devices, especially for solar and artificial photosynthetic devices, where highly concentrated porphyrins are often used for efficient light harvesting.

  14. Thermodynamic analysis of fluorescence enhancement and Quenching theory equations

    Institute of Scientific and Technical Information of China (English)

    Manman YANG; Xiaoli XI; Pin YANG

    2008-01-01

    The action of the three kinds of new third generation cephalosporin,class drugs,cefepime hydrochroride,cefpiramide and ceftizoxime with HSA and BSA was studied at different temperatures through the fluorescence method. First,the binding constants were calculated by using fluorescence quenching and enhancement theoretical equations. Their thermodynamic functions were also calculated. Because the KA corresponding to the different theoretical equations are not completely the same,the thermodynamic parameters calculated are also different. In this paper,the differences among these thermodynamic data obtained from the different theoretical equations were analyzed and the results show that the thermodynamic data deduced from fluorescence enhancement are more reasonable. Thus,we propose that even when the fluorescence quenching action of the acceptorsubstrate is studied,more realistic data can be obtained by using the fluorescence enhancement equation.

  15. Evaluation of Copper Oxide Nanoparticles Toxicity Using Chlorophyll a Fluorescence Imaging in Lemna gibba

    Directory of Open Access Journals (Sweden)

    François Perreault

    2010-01-01

    Full Text Available Copper oxide nanoparticles (CuO NPs, used in antifouling paints of boats, are released in the environment and can induce toxicity to aquatic organisms. In this report, we used chlorophyll a fluorescence imaging to evaluate CuO NPs toxicity in Lemna gibba. This approach allowed to evaluate the differential effect of CuO NPs on photosynthesis of whole L. gibba plants. Exposure to 0.1 to 0.4 g/L CuO NPs during 48h induced strong inhibition of photosynthetic processes resulting in a decrease of plant growth. By using fluorescence imaging, different photosynthetic parameters were evaluated simultaneously in microplate conditions. Imaging of FO fluorescence yield showed the decrease of leaf photosynthetic active surface for whole plants exposed to CuO NPs. This method showed that CuO NPs inhibited photosystem II maximal, photosystem II operational quantum yields, and photochemical quenching of fluorescence associated with electron transport. Nonphotochemical fluorescence quenching as an indicator of energy dissipation not used in photosynthesis was shown to be increased by the effect of CuO NPs. Such approach in microplate conditions provides synchronous high repetition measurements for numerous plants. This study may give a reliable methodological approach to evaluate toxicity risk of NPs in aquatic ecosystems.

  16. Effect of carbon and nitrogen assimilation on chlorophyll fluorescence emission by the cyanobacterium Anacystis nidulans

    Energy Technology Data Exchange (ETDEWEB)

    Romero, J.M.; Lara, C. (Instituto de Bioquimica Vegetal y Fotosintesis, Univ. de Sevilla y CSIC, Sevilla (ES)); Sivak, M.N. (Dept. of Biochemistry, Michigan State Univ., East Lansing (US))

    1992-01-01

    O{sub 2} evolution and chlorophyll A fluorescence emission have been monitored in intact cells of the cyanobacterium Anacystis nidulans 1402-1 to study the influence of carbon and nitrogen assimilation on the operation of the photosynthetic apparatus. The pattern of fluorescence induction in dark-adapted cyanobacterial cells was different from that of higher plants. Cyanobacteria undergo large, rapid state transitions upon illumination, which lead to marked changes in the fluorescence yield, complicating the estimation of quenching coefficients. The Kautsky effect was not evident, although it could be masked by a state II-state I transition, upon illumination with actinic light. The use of inhibitors of carbon assimilation such as D,L-glyceraldehyde or iodoacetamide allowed us to relate changes in variable fluorescence to active CO{sub 2} fixation. Ammonium, but not nitrate, induced non-photochemical fluorescence quenching, in agreement with a previous report on green algae, indicative of an ammonium-induced state i transition. (au).

  17. Engineered drought tolerance in tomato plants is reflected in chlorophyll fluorescence emission.

    Science.gov (United States)

    Mishra, Kumud Bandhu; Iannacone, Rina; Petrozza, Angelo; Mishra, Anamika; Armentano, Nadia; La Vecchia, Giovanna; Trtílek, Martin; Cellini, Francesco; Nedbal, Ladislav

    2012-01-01

    Drought stress is one of the most important factors that limit crop productivity worldwide. In order to obtain tomato plants with enhanced drought tolerance, we inserted the transcription factor gene ATHB-7 into the tomato genome. This gene was demonstrated earlier to be up-regulated during drought stress in Arabidopsis thaliana thus acting as a negative regulator of growth. We compared the performance of wild type and transgenic tomato line DTL-20, carrying ATHB-7 gene, under well-irrigated and water limited conditions. We found that transgenic plants had reduced stomatal density and stomatal pore size and exhibited an enhanced resistance to soil water deficit. We used the transgenic plants to investigate the potential of chlorophyll fluorescence to report drought tolerance in a simulated high-throughput screening procedure. Wild type and transgenic tomato plants were exposed to drought stress lasting 18 days. The stress was then terminated by rehydration after which recovery was studied for another 2 days. Plant growth, leaf water potential, and chlorophyll fluorescence were measured during the entire experimental period. We found that water potential in wild type and drought tolerant transgenic plants diverged around day 11 of induced drought stress. The chlorophyll fluorescence parameters: the non-photochemical quenching, effective quantum efficiency of PSII, and the maximum quantum yield of PSII photochemistry yielded a good contrast between wild type and transgenic plants from day 7, day 12, and day 14 of induced stress, respectively. We propose that chlorophyll fluorescence emission reports well on the level of water stress and, thus, can be used to identify elevated drought tolerance in high-throughput screens for selection of resistant genotypes.

  18. Fluorescence Quenching of Pheo-phytin-a by Copper(Ⅱ)Ions

    Institute of Scientific and Technical Information of China (English)

    HU,Mingbo; LI,Huaixiang; CHEN,Lusheng; ZHANG,Huaibin; DONG,Chuan

    2009-01-01

    A method was developed for determination of Cu(Ⅱ)ions quantitatively by measuring fluorescent intensity of pheophytin-a(Pheoa)solution.The Pheoa was obtained by de-intercalation of magnesium from the porphyrin ring of chlorophyll-a(Chla)extracted from fresh spinach leaves.Its two UV-Vis absorption peaks at 505 and 535 am in acetone solution have been observed but disappeared When the acetone solution of Pheoa was mixed with a Cu(Ⅱ)ion aqueous solution.A fluorescence quenching phenomenon was thus observed when the acetone solution of Pheoa was mixed with an aqueous solution of Cu(Ⅱ)ions.However,other physiologically relevant cations rarely caused any quenching fluorescence of Pheoa under the same experimental conditions.Kinetics of the fluorescence fading process Was investigated by measuring the effects of Cu(Ⅱ)ion concentration,reaction time and reaction temperature on the fluorescence intensity of the Pheoa acetone solution.An activation energy of(10±1)kJ·mol-1 was estimated from Arrhenius empirical relation assuming that the interaction between the Pheoa and the Cu(Ⅱ)ions was the first order reaction.The calibration graph obtained with the fluorescence Was linear over the Cu(Ⅱ)concentration range of 8.0×10-5-8.0×10-7 mol·dm-3 with a detection limit of 8.0×10-7 mool·dm-3 for Cu(Ⅱ)ion.

  19. Siloxanes with Pendent Naphtalene Diimides: Synthesis and Fluorescence Quenching

    NARCIS (Netherlands)

    Ganesan, P.; Lagen, van B.; Marcelis, A.T.M.; Sudhölter, E.J.R.; Zuilhof, H.

    2007-01-01

    Cyclic siloxanes with pendent naphthalene diimide groups were synthesized via hydrosilylation to form amorphous electron-accepting compounds. Photophysical measurements and >99.9% fluorescence quenching of well-known p-type polymers by the siloxanes demonstrate that these siloxanes form a new cla

  20. The Use of Chlorophyll Fluorescence Lifetime to Assess Phytoplankton Physiology within a River-Dominated Environment

    Science.gov (United States)

    Hall, Callie M.; Miller, Richard L.; Redalje, Donald G.; Fernandez, Salvador M.

    2002-01-01

    Chlorophyll a fluorescence lifetime was measured for phytoplankton populations inhabiting the three physical zones surrounding the Mississippi River's terminus in the Gulf of Mexico. Observations of river discharge volume, nitrate + nitrite, silicate, phosphate, PAR (Photosynthetically Active Radiation) diffuse attenuation within the water column, salinity, temperature, SPM, and chl a concentration were used to characterize the distribution of chl fluorescence lifetime within a given region within restricted periods of time. 33 stations extending from the Mississippi River plume to the shelf break of the Louisiana coast were surveyed for analysis of chlorophyll fluorescence lifetime during two cruises conducted March 31 - April 6, 2000, and October 24 - November 1, 2000. At each station, two to three depths were chosen for fluorescence lifetime measurement to represent the vertical characteristics of the water column. Where possible, samples were taken from just below the surface and from just above and below the pycnocline. All samples collected were within the 1% light level of the water column (the euphotic zone). Upon collection, samples were transferred to amber Nalgene bottles and left in the dark for at least 15 minutes to reduce the effects of non-photochemical quenching and to insure that photosynthetic reaction centers were open. Before measurements within the phase fluorometer were begun, the instrument was allowed to warm up for no less than one hour.

  1. Ionic quenching of naphthalene fluorescence in sodium dodecyl sulfate micelles.

    Science.gov (United States)

    Silva, Alessandra F; Fiedler, Haidi D; Nome, Faruk

    2011-03-31

    Micellar effects on luminescense of organic compounds or probes are well established, and here we show that quenching is highly favored in aqueous sodium dodecyl sulfate (SDS) micelles, which concentrate a naphthalene probe and cations of lanthanides, transition metals, and noble metals. Interactions have been studied by steady state and time-resolved fluorescence in examining the fluorescence suppression of naphthalene by metal ions in anionic SDS micelles. The quenching is collisional and correlated with the unit charge and the reduction potential of the metal ion. The rate constants, calculated in terms of local metal ion concentrations, are close to the diffusion control limit in the interior of SDS micelles, where the microscopic viscosity decreases the transfer rate, following the Stokes-Einstein relation.

  2. Intermolecular-charge-transfer-induced fluorescence quenching in protic solvent

    Science.gov (United States)

    Lin, Tao; Liu, Xiaojun; Lou, Zhidong; Hou, Yanbing; Teng, Feng

    2016-11-01

    The fluorescence quenching of fluorenone in protic solvent has been extensively investigated, and the intermolecular hydrogen bond was found to play a crucial role. Unfortunately, the mechanism at atomic level is still not clear. In the present work, we theoretically put forward the charge transfer along the hydrogen bond in the excited states. The vertical excitation energies of the fluorenone-methanol complex as well as the potential energy profiles and surfaces of the vertical excited states and charge transfer states were calculated by using the ab initio electronic-structure methods. The photochemical reactions occurring in the diverse charge transfer states were compared and their decisiveness to the fluorescence quenching was discussed in the paper.

  3. Contribution of chlorophyll fluorescence to the apparent vegetation reflectance

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, P.K. Entcheva [Joint Center for Earth Systems Technology, UMBC, Baltimore, MD 21228 (United States); Biospheric Sciences Branch, Hydrospheric and Biospheric Sciences Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States)], E-mail: pcampbel@pop900.gsfc.nasa.gov; Middleton, E.M. [Biospheric Sciences Branch, Hydrospheric and Biospheric Sciences Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States); Corp, L.A. [Biospheric Sciences Branch, Hydrospheric and Biospheric Sciences Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States); Agricultural Research Service, USDA, Beltsville, MD 20705 (United States); Kim, M.S. [Agricultural Research Service, USDA, Beltsville, MD 20705 (United States)

    2008-10-15

    Current strategies for monitoring the physiologic status of terrestrial vegetation rely on remote sensing reflectance data, which provide estimates of vigor based primarily on chlorophyll content. Chlorophyll fluorescence (ChlF) measurements offer a non-destructive alternative and a more direct approach for diagnosis of vegetation stress before a significant reduction in chlorophyll content has occurred. Thus, technology based on ChlF may allow more accurate carbon sequestration estimates and earlier stress detection than is possible when using reflectance data alone. However, the observed apparent vegetation reflectance (Ra) in reality includes contributions from both the reflected and fluoresced radiation. The aim of this study is to determine the relative contributions of reflectance and ChlF fractions to Ra in the red to near-infrared region (650-800 nm) of the spectrum. The practical objectives of the study are to: 1) evaluate the relationship between ChlF and reflectance at the foliar level for corn, soybean and maple; and 2) for corn, determine if the relationship established for healthy vegetation changes under nitrogen (N) deficiency. To obtain generally applicable results, experimental measurements were conducted on unrelated crop and tree species (corn, soybean and maple) under controlled conditions and a gradient of inorganic N fertilization levels. Optical reflectance spectra and actively induced ChlF emissions were collected on the same foliar samples, in conjunction with measurements of photosynthetic function, pigment levels, and carbon (C) and N content. The spectral trends were examined for similarities. On average, 10-20% of Ra at 685 nm was actually due to ChlF. The spectral trends in steady state and maximum fluorescence varied significantly, with steady state fluorescence (especially red, 685 nm) showing higher ability for species and treatment separation. The relative contribution of ChlF to Ra varied significantly among species, with maple

  4. Neodymium Fluorescence Quenching by Hydroxyl Groups in Phosphate Laser Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ehrmann, P R; Carlson, K; Campbell, J H; Click, C A; Brow, R K

    2003-09-02

    Non-radiative losses due to OH fluorescence quenching of the Nd{sup 3+} {sup 4}F{sub 3/2} state are quantified over a range of OH concentrations from 4 x 10{sup 18}/cm{sup 3} to 4 x 10{sup 20}/cm{sup 3} and Nd doping levels from 0.4 to 9 x 10{sup 20}/cm{sup 3} in two K{sub 2}O-MgO-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5} metaphosphate glasses having different K/Mg ratios ({approx}1/1 and 2/1). The quenching rate is found to vary linearly with the Nd and OH concentrations as predicted by Forster-Dexter theory. However, in contrast to theory the OH quenching rate extrapolates to a non-zero value at low Nd{sup 3+} doping levels. It is proposed that at low Nd{sup 3+} concentrations the OH is correlated with Nd sites in the glass. The quenching strength of OH on a per ion basis is found to be weak compared to other common transition metal impurities (e.g. Fe{sup 2+}, Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}). Nevertheless, OH dominates the Nd quenching in phosphate glass because under most processing conditions OH is present at concentrations 10{sup 2} to 10{sup 3} greater than transition metal ion impurities. A correlation of the quenching strength of OH and common metal impurity ions with the degree of spectral overlap of the impurity absorption bands and the four {sup 4}F{sub 3/2} to {sup 4}I{sub J} transitions shows good agreement.

  5. Effect of Methanol on Photosynthesis and Chlorophyll Fluorescence of Flag Leaves of Winter Wheat

    Institute of Scientific and Technical Information of China (English)

    ZHENG Yue-jin; YANG Yue-qin; LIANG Shan-shan; YI Xian-feng

    2008-01-01

    Photosynthesis and chlorophyll a fluorescence parameters, photochemical efficiency of PS II (Fv/Fm), photochemical quenching of PS II (qP), nonphotochemical quenching of PS II (NPQ), maximum activity of PS II (Fv/Fo) as well as electron transport rate (ETR), and quantum yield of PS II (ΦPS II) were measured on flag leaves of the winter wheat treated by methanol at different concentrations. The results revealed that photosynthesis was greatly improved by methanol, as indicated by higher photosynthetic rates and stomatal conductance. The enhancement effect of methanol on photosynthesis was maintained for 3-4 days. Different methanol concentration treatments also increased intercellular CO2 concentration and transpiration rates. No significant decline was found in Fv/Fm, Fv/Fo, and ΦPS II, which revealed no photoinhibition during methanol application in different methanol concentrations. Methanol showing no apparent inhibitory effects indicated higher potential photosynthetic capacity of flag leaves of winter wheat. However, the increase in photosynthesis was not followed by an increase in the photosynthetic activity (Fv/Fm), and fluorescence parameters did not indicate an improvement in intercellular CO2 concentration and PS II photochemical efficiency compared with the control, thereby encouraging us to propose that lower leaf temperatures caused by applied methanol would reduce both dark respiration and photorespiration (most importantly), thus, increasing net CO2 uptake and photosynthetic rates.

  6. Photophysical behavior and fluorescence quenching by halides of quinidine dication: Steady state and time resolved study

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Neeraj Kumar; Tewari, Neeraj; Arora, Priyanka; Rautela, Ranjana; Pant, Sanjay [Photophysics Laboratory, Department of Physics, DSB Campus, Kumaun University, Nainital 263002, Uttarakhand (India); Joshi, Hem Chandra, E-mail: hem_sup@yahoo.co.uk [Institute for Plasma Research, Laser Diagnostics Division, Bhat, Near Indira Bridge, Gandhinagar 382428, Gujarat (India)

    2015-02-15

    The fluorescence quenching of quinidine in acidified aqueous solution by various halides (Cl{sup −}, Br{sup −} and I{sup −}) was studied using steady state and time resolved fluorescence techniques. The quenching process was characterized by Stern–Volmer (S–V) plots. Possibility of conformers (one is not quenched by halide and the other is quenched) is invoked to explain the observed results. - Highlights: • Fluorescence quenching of quinidine in acidified aqueous solution by halides. • Various quenching parameters have been estimated. • Possibility of conformers is invoked to explain the observed results.

  7. Variability of the specific fluorescence of chlorophyll in the ocean. Part 2. Fluorometric method of chlorophyll a determination

    Directory of Open Access Journals (Sweden)

    Miros³awa Ostrowska

    2000-06-01

    Full Text Available Two methods of determining the chlorophyll a concentration in the sea have been formulated on the basis of artificially induced fluorescence measured with the aid of submersible fluorometers. The method of statistical correlation is founded on the empirical relationship between fluorescence and chlorophyll concentration. The theoretical model of fluorescence described in Part 1 of this paper (see Ostrowska et al. 2000, this volume provides the basis of the other method, the physical method. This describes the dependence of the specific fluorescence of phytoplankton on the chlorophyll concentration, a diversity of photophysiological properties of phytoplankton and the optical characteristics of the fluorometer.     In order to assess their practicability, the methods were subjected to empirical verification. This showed that the physical method yielded chlorophyll concentrations of far greater accuracy. The respective error factors of the estimated chlorophyll concentration were x = 2.07 for the correlation method and x = 1.5 for the physical method. This means that the statistical logarithmic error varies from -52 to +107% in the case of the former method but only from -33 to +51% in the case of the latter. Thus, modifying the methodology has much improved the accuracy of chlorophyll determinations.

  8. Radioactivity-synchronized fluorescence enhancement using a radionuclide fluorescence-quenched dye.

    Science.gov (United States)

    Berezin, Mikhail Y; Guo, Kevin; Teng, Bao; Edwards, W Barry; Anderson, Carolyn J; Vasalatiy, Olga; Gandjbakhche, Amir; Griffiths, Gary L; Achilefu, Samuel

    2009-07-08

    We demonstrate the first evidence of radioactivity-synchronized fluorescence quenching of a near-infrared light-emitting dye by a radionuclide, (64)Cu, and subsequent fluorescence enhancement upon (64)Cu decay to the daughter isotopes (64)Ni and (64)Zn. The dynamic switch from high radioactivity and low fluorescence to low radioactivity and high fluorescence is potentially useful for developing complementary multimodal imaging and detection platforms for chemical, environmental, and biomedical applications as well as for unraveling the mechanisms of metal-induced dynamic fluorescence changes.

  9. Leaf Gas Exchange and Chlorophyll a Fluorescence Imaging of Rice Leaves Infected with Monographella albescens.

    Science.gov (United States)

    Tatagiba, Sandro Dan; DaMatta, Fábio Murilo; Rodrigues, Fabrício Ávila

    2015-02-01

    This study was intended to analyze the photosynthetic performance of rice leaf blades infected with Monographella albescens by combining chlorophyll (Chl) a fluorescence images with gas exchange and photosynthetic pigment pools. The net CO2 assimilation rate, stomatal conductance, transpiration rate, total Chl and carotenoid pools, and Chl a/b ratio all decreased but the internal CO2 concentration increased in the inoculated plants compared with their noninoculated counterparts. The first detectable changes in the images of Chl a fluorescence from the leaves of inoculated plants were already evident at 24 h after inoculation (hai) and increased dramatically as the leaf scald lesions expanded. However, these changes were negligible for the photosystem II photochemical efficiency (Fv/Fm) at 24 hai, in contrast to other Chl fluorescence traits such as the photochemical quenching coefficient, yield of photochemistry, and yield for dissipation by downregulation; which, therefore, were much more sensitive than the Fv/Fm ratio in assessing the early stages of fungal infection. It was also demonstrated that M. albescens was able to impair the photosynthetic process in both symptomatic and asymptomatic leaf areas. Overall, it was proven that Chl a fluorescence imaging is an excellent tool to describe the loss of functionality of the photosynthetic apparatus occurring in rice leaves upon infection by M. albescens.

  10. Changes of Photosystem Ⅱ Electron Transport in the Chlorophyll-deficient Oilseed Rape Mutant Studied by Chlorophyll Fluorescence and Thermoluminescence

    Institute of Scientific and Technical Information of China (English)

    Jun-Wei Guo; Jin-Kui Guo; Yun Zhao; Lin-Fang Du

    2007-01-01

    The photosystem Ⅱ (PSII) complex of photosynthetic membranes comprises a number of chlorophyll-binding proteins that are important to the electron flow. Here we report that the chlorophyll b-deficient mutant has de creased the amount of light-harvesting complexes with an increased amount of some core polypeptides of PSII,including CP43 and CP47. By means of chlorophyll fluorescence and thermoluminescence, we found that the ratio of Fv/Fm, qP and electron transport rate in the chlorophyll b-deficient mutant was higher compared to the wild type.In the chlorophyll b-deficient mutant, the decay of the primary electron acceptor quinones (QA-) reoxidation was decreased, measured by the fluorescence. Furthermore, the thermolumlnescence studies in the chlorophyll b deficient mutant showed that the B band (S2/S3QB-) decreased slightly and shifted up towards higher temperatures.In the presence of dichlorophenyl-dimethylurea, which is inhibited in the electron flow to the second electron acceptor quinines (QB) at the PSII acceptor side, the maximum of the Q band (S2QA-) was decreased slightly and shifted down to lower temperatures, compared to the wild type. Thus, the electron flow within PSll of the chlorophyll b-deficient mutant was down-regulated and characterized by faster oxidation of the primary electron acceptor quinine QA- via forward electron flow and slower reduction of the oxidation S states.

  11. Photosynthesis, chlorophyll fluorescence characteristics, and chlorophyll content of soybean seedlings under combined stress of bisphenol A and cadmium.

    Science.gov (United States)

    Hu, Huiqing; Wang, Lihong; Wang, Qingqing; Jiao, Liya; Hua, Weiqi; Zhou, Qing; Huang, Xiaohua

    2014-11-01

    Bisphenol A (BPA) is ubiquitous in the environment because of its continual application in plastics and the epoxy resin industry. Cadmium (Cd) is a highly toxic heavy metal element mainly used in smelting, electroplating, and plastic and dye manufacturing. Pollution as a result of BPA and Cd exists simultaneously in many agricultural regions. However, little information is available regarding the combined effects of BPA and Cd on plants. The combined effects of BPA and Cd on the photosynthesis, chlorophyll fluorescence, and chlorophyll content of soybean seedlings were investigated using noninvasive technology. Combined treatment with 1.5 mg/L BPA and 0.2 mg/L Cd synergistically improved the net photosynthetic rate (Pn ), initial fluorescence (F0 ), maximal photochemical efficiency (Fv /Fm ), effective quantum yield of photosystem II (ΦPSII ), photosynthetic electron transport rate (ETR), and chlorophyll content. Combined treatment with 1.5 mg/L BPA and 3.0 mg/L Cd increased the F0 and decreased the Pn , Fv /Fm , ΦPSII , and ETR, whereas BPA and Cd exhibited an antagonistic effect. Furthermore, combined treatment with 17.2/50.0 mg/L BPA and 3.0/10.0 mg/L Cd synergistically decreased the Pn , Fv /Fm , ΦPSII , ETR, and chlorophyll content, although it increased the F0 . Finally, the effects of BPA and Cd on photosynthesis, chlorophyll fluorescence, and chlorophyll content ceased when BPA stress was stopped.

  12. Canopy Level Chlorophyll Fluorescence and the PRI in a Cornfield

    Science.gov (United States)

    Middleton, Elizabeth M.; Cheng, Yen-Ben; Corp, Lawrence A.; Campbell, Petya K. E.; Huemmrich, K. Fred; Zhang, Qingyuan; Kustas, William P.

    2012-01-01

    Two bio-indicators, the Photochemical Reflectance Index (PRI) and solar-induced red and far-red Chlorophyll Fluorescence (SIF), were derived from directional hyperspectral observations and studied in a cornfield on two contrasting days in the growing season. Both red and far-red SIF exhibited higher values on the day when the canopy in the early senescent stage, but only the far-red SIF showed sensitivity to viewing geometry. Consequently, the red/far-red SIF ratio varied greatly among azimuth positions while the largest values were obtained for the "hotspot" at both growth stages. This ratio was lower (approx.0.88 +/- 0.4) in early July than in August when the ratio approached equivalence (near approx.1). In concert, the PRI exhibited stronger responses to both zenith and azimuth angles and different values on the two growth stages. The potential of using these indices to monitor photosynthetic activities needs further investigation

  13. Combined Quenching Mechanism of Anthracene Fluorescence by Cetylpyridinium Chloride in Sodium Dodecyl Sulfate Micelles.

    Science.gov (United States)

    Soemo, Angela R; Pemberton, Jeanne E

    2014-03-01

    The Stern-Volmer quenching constant (KSV) for quenching of anthracene fluorescence in sodium dodecyl sulfate (SDS) micelles by pyridinium chloride has been reported previously to be 520 M(-1) based on steady state fluorescence measurements. However, such measurements cannot distinguish static versus dynamic contributions to the overall quenching. In the work reported here, the quenching dynamics of anthracene in SDS micelles by cetylpyridinium chloride (CPC), an analogue of pyridinium chloride, were investigated using both steady state and time resolved fluorescence quenching. Concurrent measurement of the decrease in fluorescence intensity and lifetime of anthracene provide a quantitative evaluation of collision induced (i.e. dynamic) versus complex formation (i.e. static) quenching of the anthracene fluorophore. The results reveal that a combined quenching mechanism is operative with approximately equal constants of 249 ± 6 M(-1) and 225 ± 12 M(-1) for dynamic and static quenching, respectively.

  14. Effects of LEDs on chlorophyll fluorescence and secondary metabolites in Phalaenopsis

    DEFF Research Database (Denmark)

    Ouzounis, T.; Fretté, X.; Rosenqvist, Eva

    2015-01-01

    of the experiment. Chlorophyll fluorescence was also recorded with PAM-2001. Leaf area and total fresh weight were highest in the 40%B/60%R for Phalaenopsis 'Vivien', while 100%R demonstrated the highest leaf area and fresh weight for Phalaenopsis 'Purple star'. Chlorophyll fluorescence for the same treatments...

  15. Contribution of Chlorophyll Fluorescence to the Apparent Reflectance of Vegetation

    Science.gov (United States)

    Campbell, P. K. Entcheva; Middleton, E. M.; Kim, M. S.

    2007-01-01

    Current strategies for monitoring the physiologic status of terrestrial vegetation rely on remote sensing reflectance (R) measurements, whi ch provide estimates of relative vegetation vigor based primarily on chlorophyll content. Vegetation chlorophyll fluorescence (CF) offers a non-destructive alternative and a more direct approach for diagnosis of vegetation stress before a significant reduction in chlorophyll content has occurred. Thus, monitoring of vegetation vigor based on CF may allow earlier stress detection and more accurate carbon sequestra tion estimates, than is possible using R data alone. However, the observed apparent vegetation reflectance (Ra) in reality includes contrib utions from both the reflected and fluoresced radiation. The aim of t his study is to determine the relative R and CF fractions contributing to Ra from the vegetation in the red to near-infrared region of the spectrum. The practical objectives of the study are to: 1) evaluate t he relationship between CF and R at the foliar level for corn, soybean, maple; and 2) for corn, determine if the relationship established f or healthy (optimal N) vegetation changes under N defiiency. To obtai n generally applicable results, experimental measurements were conducted on unrelated crop and tree species (maple, soybean and corn), unde r controlled conditions and a gradient of inorganic N fertilization l evels. Optical R spectra and actively induced CF emissions were obtained on the same foliar samples, in conjunction with measurements of p hotosynthetic function, pigment levels, and C and N content. The comm on spectral trends or similarities were examined. On average, 10-20% of apparent R at 685 nm was actually due to CF. The spectral trends in steady and maximum F varied significantly, with Fs (especially red) showing higher ability for species and treatment separation. The relative contribution of ChF to R varied significantly among species, with maple emitting much higher F amounts, as

  16. Mechanism of fluorescence quenching of tyrosine derivatives by amide group

    Science.gov (United States)

    Wiczk, Wiesław; Rzeska, Alicja; Łukomska, Joanna; Stachowiak, Krystyna; Karolczak, Jerzy; Malicka, Joanna; Łankiewicz, Leszek

    2001-06-01

    The difference between fluorescence lifetimes of the following amino acids: phenylalanine (Phe), tyrosine (Tyr), ( O-methyl)tyrosine (Tyr(Me)), (3-hydroxy)tyrosine (Dopa), (3,4-dimethoxy)phenylalanine (Dopa(Me) 2) and their amides was used to testify the mechanism of fluorescence quenching of aromatic amino acids by the amide group. On the basis of the Marcus theory of photoinduced electron transfer parabolic relationships between ln kET and ionization potentials reduced by energy of excitation ( IP-E ∗0,0) for the above-mentioned amino acids were obtained. This finding indicates the occurrence of photoinduced electron transfer from the excited chromophore group to the amide group.

  17. [Effects of controlled-release fertilizer on chrysanthemum leaf chlorophyll fluorescence characteristics and ornamental quality].

    Science.gov (United States)

    Song, Xu-xu; Zheng, Cheng-shu; Sun, Xia; Ma, Hai-yan

    2011-07-01

    Taking cut flower chrysanthemum 'Baima' as test material, a pot experiment was conducted to study the effects of controlled-release fertilizer on the leaf chlorophyll fluorescence parameters, chlorophyll and nutrient contents, and ornamental quality of chrysanthemum. Under no fertilization, the maximal photochemical efficiency of PS II in dark (F(v)/F(m)), potential photochemical efficiency of PS II (F(v)/F(0)), and quantum yield of PS II electron transport (phi(PS II)) decreased significantly, compared with those under fertilization. With the application of conventional compound fertilizers CCFA (N:P:K=20:8:10) and CCFB (N:P:K= 14:14:14), the F(v)/F(m), F(v)/F(0) and phi(PS II) had a slight increase in early period (30-60 d) but a remarkable decrease in mid and later periods (75 - 120 d), compared with those under the application of controlled-release fertilizers CRFA (N:P:K = 20:8:10) and CRFB (N:P:K= 14:14:14). Under the application of CRFA, the F(v)/F(m), phi(PS II), and photochemical quenching (q(P)) had somewhat increase, as compared with the application of CRFB. The non-photochemical quenching (NPQ) under the application of CRFA and CRFB decreased significantly, compared with that under the application of CCFA and CCFB and the control. The chlorophyll content had a similar change trend with F(v)/F(m), F(v)/F(0), and phi(PS II). The leaf N, P, and K contents, flower stalk length and stalk diameter, flower diameter, and flower fresh and dry mass at harvest stage all increased under the application of CRFA and CRFB, compared with those under the application of CCFA and CCFB and the control, and the flower fresh and dry mass was significantly higher under the application of CRFA than of CRFB. This study showed that controlled-release fertilizer could improve the ornamental quality of chrysanthemum via improving the leaf chlorophyll content, photochemical transduction rate, and nutrient uptake, and CRFA had better effects than CRFB.

  18. [Study on the characters of phytoplankton chlorophyll fluorescence excitation spectra based on fourth-derivative].

    Science.gov (United States)

    Lu, Lu; Su, Rong-Guo; Wang, Xiu-Lin; Zhu, Chen-Jian

    2007-11-01

    Chlorophyll fluorescence excitation spectra of six phytoplankton species, belonging to Bacillariophyta and Dinophyta, were dealt by fourth-derivative analysis with the Matlab program. The results show that between 350 nm and 550 nm six fluorescence peaks were found in the fourth-derivative spectra, which are representatives of non-pigments, chlorophylls and carotenoides respectively. The method makes Bacillariophyta and Dinophyta more distinguishable when the fourth-derivative spectra are compared with the chlorophyll fluorescence excitation spectra. It can be used not only to discriminate the two groups of algaes, but also to reduce the effect of noise. The fluorescence peaks in the fourth-derivative spectra are proved to be stable.

  19. Non-photochemical fluorescence quenching and the diadinoxanthin cycle in a marine diatom.

    Science.gov (United States)

    Olaizola, M; La Roche, J; Kolber, Z; Falkowski, P G

    1994-08-01

    The diadinoxanthin cycle (DD-cycle) in chromophyte algae involves the interconversion of two carotenoids, diadinoxanthin (DD) and diatoxanthin (DT). We investigated the kinetics of light-induced DD-cycling in the marine diatom Phaeodactylum tricornutum and its role in dissipating excess excitation energy in PS II. Within 15 min following an increase in irradiance, DT increased and was accompanied by a stoichiometric decrease in DD. This reaction was completely blocked by dithiothreitol (DTT). A second, time-dependent, increase in DT was detected ∼ 20 min after the light shift without a concomitant decrease in DD. DT accumulation from both processes was correlated with increases in non-photochemical quenching of chlorophyll fluorescence. Stern-Volmer analyses suggests that changes in non-photochemical quenching resulted from changes in thermal dissipation in the PS II antenna and in the reaction center. The increase in non-photochemical quenching was correlated with a small decrease in the effective absorption cross section of PS II. Model calculations suggest however that the changes in cross section are not sufficiently large to significantly reduce multiple excitation of the reaction center within the turnover time of steady-state photosynthetic electron transport at light saturation. In DTT poisoned cells, the change in non-photochemical quenching appears to result from energy dissipation in the reaction center and was associated with decreased photochemical efficiency. D1 protein degradation was slightly higher in samples poisoned with DTT than in control samples. These results suggest that while DD-cycling may dynamically alter the photosynthesis-irradiance response curve, it offers limited protection against photodamage of PS II reaction centers at irradiance levels sufficient to saturate steady-state photosynthesis.

  20. Chlorophyll bleaching by UV-irradiation in vitro and in situ: Absorption and fluorescence studies

    Energy Technology Data Exchange (ETDEWEB)

    Zvezdanovic, Jelena [Faculty of Technology, University of Nish, Bulevar oslobodjenja 124, 16000 Leskovac (Serbia)], E-mail: jelite74@yahoo.com; Cvetic, Tijana [Faculty of Biology, University of Belgrade, Takovska 43, Belgrade 11000 (Serbia); Veljovic-Jovanovic, Sonja [Center for Multidisciplinary Studies, University of Belgrade, Kneza Viseslava la, Belgrade 11030 (Serbia); Markovic, Dejan [Faculty of Technology, University of Nish, Bulevar oslobodjenja 124, 16000 Leskovac (Serbia)], E-mail: dejan_markovic57@yahoo.com

    2009-01-15

    Chlorophyll bleaching by UV-irradiation has been studied by absorbance and fluorescence spectroscopy in extracts containing mixtures of photosynthetic pigments, in acetone and n-hexane solutions, and in aqueous thylakoid suspensions. Chlorophyll undergoes destruction (bleaching) accompanied by fluorescent transient formation obeying first-order kinetics. The bleaching is governed by UV-photon energy input, as well as by different chlorophyll molecular organizations in solvents of different polarities (in vitro), and in thylakoids (in situ). UV-C-induced bleaching of chlorophylls in thylakoids is probably caused by different mechanisms compared to UV-A- and UV-B-induced bleaching.

  1. Chlorophyll Fluorescence and Dynamic Xanthophyll Reflectance as Methods to Estimate Photosynthesis with Remote Sensors - A Modelling Approach

    Science.gov (United States)

    Vilfan, N.; Van der Tol, C.; Verhoef, W.

    2016-12-01

    Chlorophyll fluorescence (ChlF) has been proven valuable in studying the dynamics of photosynthesis: together with the photochemical reflectance index (PRI), which reflects the changes in reflectance around 535 nm due to the xanthophyll cycle effect, it offers a powerful way to non-destructively quantify plant photosynthetic and dissipation activity from leaf to potentially global scale. We present an extended simulation model, Fluspect, for the transfer of light within the leaf as a function of its pigment contents and structure. Output of the model are reflectance and transmittance spectra of the leaf as well as ChlF spectra. From ChlF spectra, fluorescence quantum efficiency parameters (η) of photosystems I and II can be retrieved. Moreover, we extended and parameterized Fluspect by including a physically based description of the dynamic xanthophyll reflectance (XR). We introduced a new, retrievable parameter, V2Z, for the status of the XR. Finally, we combined the model Fluspect with a simple enzyme kinetics model of photosynthesis. In this study, we explore the combined model by using relations among photochemical quenching (PQ), non-photochemical quenching (NPQ), V2Z and η. We explore these relationships by using multiple available datasets, where measurements were by different combinations of the following methods: (1) hyperspectral leaf reflectance in visible to NIR region together with ChlF spectra, (2) gas exchange, and (3) Pulse Amplitude Modulated (PAM) fluorescence. The aim of the study is to explore the relationships between the two fundamentally different components, namely the transfer of light within the leaf and the enzyme kinetics of photosynthesis. Moreover, it is now possible to simulate dynamic xanthophyll reflectance and chlorophyll fluorescence quenching simultaneously, which is relevant for the remote sensing of photosynthesis.

  2. ΔpH-dependent non-photochemical quenching (qE) of excited chlorophylls in the photosystem II core complex of the freshwater cyanobacterium Synechococcus sp PCC 7942.

    Science.gov (United States)

    Stamatakis, Kostas; Papageorgiou, George C

    2014-08-01

    Light-induced and lumen acidity-dependent quenching (qE) of excited chlorophylls (Chl) in vivo has been amply documented in plants and algae, but not in cyanobacteria, using primarily the saturation pulse method of quenching analysis which is applied to continuously illuminated samples. This method is unsuitable for cyanobacteria because the background illumination elicits in them a very large Chl a fluorescence signal, due to a state 2 to state 1 transition, which masks fluorescence changes due to other causes. We investigated the qE problem in the cyanobacterium Synechococcus sp. PCC 7942 using a kinetic method (Chl a fluorescence induction) with which qE can be examined before the onset of the state 2 to state 1 transition and the attendant rise of Chl a fluorescence. Our results confirm the existence of a qE mechanism that operates on excited Chls a in Photosystem II core complexes of cyanobacteria.

  3. Detection of herbicide effects on pigment composition and PSII photochemistry in Helianthus annuus by Raman spectroscopy and chlorophyll a fluorescence.

    Science.gov (United States)

    Vítek, Petr; Novotná, Kateřina; Hodaňová, Petra; Rapantová, Barbora; Klem, Karel

    2017-01-01

    The effects of herbicides from three mode-of-action groups - inhibitors of protoporphyrinogen oxidase (carfentrazone-ethyl), inhibitors of carotenoid biosynthesis (mesotrione, clomazone, and diflufenican), and inhibitors of acetolactate synthase (amidosulfuron) - were studied in sunflower plants (Helianthus annuus). Raman spectroscopy, chlorophyll fluorescence (ChlF) imaging, and UV screening of ChlF were combined to evaluate changes in pigment composition, photosystem II (PSII) photochemistry, and non-photochemical quenching in plant leaves 6d after herbicide application. The Raman signals of phenolic compounds, carotenoids, and chlorophyll were evaluated and differences in their intensity ratios were observed. Strongly augmented relative content of phenolic compounds was observed in the case of amidosulfuron-treated plants, with a simultaneous decrease in the chlorophyll/carotenoid intensity ratio. The results were confirmed by in vivo measurement of flavonols using UV screening of ChlF. Herbicides from the group of carotenoid biosynthesis inhibitors significantly decreased both the maximum quantum efficiency of PSII and non-photochemical quenching as determined by ChlF. Resonance Raman imaging (mapping) data with high resolution (150,000-200,000 spectra) are presented, showing the distribution of carotenoids in H. annuus leaves treated by two of the herbicides acting as inhibitors of carotenoid biosynthesis (clomazone or diflufenican). Clear signs were observed that the treatment induced carotenoid depletion within sunflower leaves. The depletion spatial pattern registered differed depending on the type of herbicide applied.

  4. Detection of herbicide effects on pigment composition and PSII photochemistry in Helianthus annuus by Raman spectroscopy and chlorophyll a fluorescence

    Science.gov (United States)

    Vítek, Petr; Novotná, Kateřina; Hodaňová, Petra; Rapantová, Barbora; Klem, Karel

    2017-01-01

    The effects of herbicides from three mode-of-action groups - inhibitors of protoporphyrinogen oxidase (carfentrazone-ethyl), inhibitors of carotenoid biosynthesis (mesotrione, clomazone, and diflufenican), and inhibitors of acetolactate synthase (amidosulfuron) - were studied in sunflower plants (Helianthus annuus). Raman spectroscopy, chlorophyll fluorescence (ChlF) imaging, and UV screening of ChlF were combined to evaluate changes in pigment composition, photosystem II (PSII) photochemistry, and non-photochemical quenching in plant leaves 6 d after herbicide application. The Raman signals of phenolic compounds, carotenoids, and chlorophyll were evaluated and differences in their intensity ratios were observed. Strongly augmented relative content of phenolic compounds was observed in the case of amidosulfuron-treated plants, with a simultaneous decrease in the chlorophyll/carotenoid intensity ratio. The results were confirmed by in vivo measurement of flavonols using UV screening of ChlF. Herbicides from the group of carotenoid biosynthesis inhibitors significantly decreased both the maximum quantum efficiency of PSII and non-photochemical quenching as determined by ChlF. Resonance Raman imaging (mapping) data with high resolution (150,000-200,000 spectra) are presented, showing the distribution of carotenoids in H. annuus leaves treated by two of the herbicides acting as inhibitors of carotenoid biosynthesis (clomazone or diflufenican). Clear signs were observed that the treatment induced carotenoid depletion within sunflower leaves. The depletion spatial pattern registered differed depending on the type of herbicide applied.

  5. Chlorophyll a fluorescence induction (Kautsky curve) in a Venus flytrap (Dionaea muscipula) leaf after mechanical trigger hair irritation.

    Science.gov (United States)

    Vredenberg, Wim; Pavlovič, Andrej

    2013-02-15

    This paper describes experiments on transient changes in chlorophyll a fluorescence in traps of the carnivorous plant Venus flytrap (Dionaea muscipula) that occur in association with mechanical stimulation of trigger hairs and propagation of action potentials (APs). The experiments show the following reproducible effects of APs on the fluorescence induction (Kautsky-, or OJIPSMT curve) in a 100 s low intensity light pulse (i) no change in the OJ phase attributed to release of photochemical quenching, (ii) a small enhancement, if at all of increase in the thermal JIP phase, (iii) a two- to threefold deceleration of the fluorescence decline (quenching) during the PSMT phase in the 2-100 s time range, and (iv) a transient 15-50% increase in variable fluorescence within ~20 s under steady state light condition with, after ~80 s, a 10% undershoot that reverses in several tens of seconds to the original steady state. The results are discussed in terms of a hypothesis that the fluorescence decline during the SMT phase of the Kautsky induction curve, attributed to NPQ, is caused by the Δμ(H+)-driven increase in proton conductance of the CF(o) channel of the ATPase during its activation. A signal-transducing role of Ca(2+) is suggested. Copyright © 2012 Elsevier GmbH. All rights reserved.

  6. Fluorescence Quenching of Benzaldehyde in Water by Hydrogen Atom Abstraction.

    Science.gov (United States)

    Fletcher, Katharyn; Bunz, Uwe H F; Dreuw, Andreas

    2016-09-01

    We computed the mechanism of fluorescence quenching of benzaldehyde in water through relaxed potential energy surface scans. Time-dependent density functional theory calculations along the protonation coordinate from water to benzaldehyde reveal that photoexcitation to the bright ππ* (S3 ) state is immediately followed by ultrafast decay to the nπ* (S1 ) state. Evolving along this state, benzaldehyde (BA) abstracts a hydrogen atom, resulting in a BAH(.) and OH(.) radical pair. Benzaldehyde does not act as photobase in water, but abstracts a hydrogen atom from a nearby solvent molecule. The system finally decays back to the ground state by non-radiative decay and an electron transfers back to the OH(.) radical. Proton transfer from BAH(+) to OH(-) restores the initial situation, BA in water.

  7. Chlorophyll fluorescence in vivo as a probe for rapid measurement of tolerance to ultraviolet radiation

    Energy Technology Data Exchange (ETDEWEB)

    Smillie, R.M. (Macquarie Univ., North Ryde (Australia). School of Biological Sciences)

    1983-02-01

    Chlorophyll fluorescence in vivo was progressively lost in pea leaves irradiated with either short or long-wave light. The changes were consistent with the development in the intact leaves of an inhibitory site on the photooxidizing side of photosystem II. In contrast, leaves of two species of Agave, plants regarded as more resistant to UV radiation, showed only minor changes in chlorophyll fluorescence. Agave americana was affected less than A. attenuata. The application of measurements of chlorophyll fluorescence in vivo to screening for tolerance to UV radiation is discussed.

  8. Chlorophyll content and chlorophyll fluorescence in tomato leaves infested with an invasive mealybug, Phenacoccus solenopsis (Hemiptera: Pseudococcidae).

    Science.gov (United States)

    Huang, Jun; Zhang, Peng-Jun; Zhang, Juan; Lu, Yao-Bin; Huang, Fang; Li, Ming-Jiang

    2013-10-01

    Herbivore injury has indirect effects on the growth and performance of host plants through photosynthetic suppression. It causes uncertain reduction in photosynthesis, which likely depends on the degree of infestation. Rapid light curves provide detailed information on the saturation characteristics of electron transport as well as the overall photosynthetic performance of a plant. We examined the effects of different intensities of infestation of the invasive mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae), on the relative chlorophyll content and rapid light curves of tomato Solanum lycopersicum L. leaves using a chlorophyll meter and chlorophyll fluorescence measurement system, respectively, under greenhouse conditions. After 38 d of P. solenopsis feeding, relative chlorophyll content of tomato plants with initial high of P. solenopsis was reduced by 57.3%. Light utilization efficiency (α) for the initial high-density treatment was reduced by 42.4%. However, no significant difference between initial low-density treatment and uninfested control was found. The values of the maximum electron transport rate and minimum saturating irradiance for initial high-density treatment were reduced by 82.0 and 69.7%, respectively, whereas the corresponding values for low-density treatment were reduced by 55.9 and 58.1%, respectively. These data indicated that changes were induced by P. solenopsis feeding in the relative chlorophyll content and chlorophyll fluorescence of infested tomato plants. The results indicating that low initial infestation by P. solenopsis caused no change in relative leaf chlorophyll content or light utilization efficiency could have been because the plants rapidly adapted to P. solenopsis feeding or because of compensatory photosynthesis.

  9. Effects of Nitrogen Fertilizer Level on Chlorophyll Fluorescence Characteristics in Flag Leaf of Super Hybrid Rice at Late Growth Stage

    Institute of Scientific and Technical Information of China (English)

    LONG Ji-rui; MA Guo-hui; WAN Yi-zheng; SONG Chun-fang; SUN Jian; QIN Rui-jun

    2013-01-01

    To compare the effects of slow-release nitrogen fertilizer at six different levels on the flag leaf chlorophyll fluorescence characteristics of super hybrid rice,a field fertilization experiment was conducted with super hybrid rice Y Liangyou 1 as a test material.The photosynthetic electron transport rate (ETR),effective quantum yield (EQY),photochemical quenching coefficient (qp),and non-photochemical quenching coefficient (NPQ) of flag leaves were measured at the initial heading,full heading,10 d after full heading and 20 d after full heading stages.Results showed that the values of ETR,EQY and qp increased with rice development from initial heading to 20 d after full heading,whereas the NPQ decreased.During the measured stages,ETR,EQY and qp increased initially and then decreased as nitrogen application amount increased,but they peaked at different nitrogen fertilizer levels.The maximum ETR and EQY values appeared at the treatment of 135 kg/hm2 N.In conclusion,the optimum nitrogen amount for chlorophyll fluorescence characteristics of super hybrid rice was 135-180 kg/hm2.

  10. Dynamic fluorescence quenching of quinine sulfate dication by chloride ion in ionic and neutral micellar environments

    Science.gov (United States)

    Joshi, Sunita; Varma Y, Tej Varma; Pant, Debi D.

    2014-04-01

    Fluorescence quenching of Quinine sulfate dication (QSD) by chloride-ion (Cl-) in micellar environments of anionic, sodium dodecyl sulfate (SDS), cationic, cetyltrimethylammonium bromide (CTAB) and neutral, triton X-100 (TX-100) in aqueous phase has been investigated by time-resolved and steady- state fluorescence measurements. The quenching follows linear Stern-Volmer relation in micellar solutions and is dynamic in nature.

  11. Fo-spectra of chlorophyll fluorescence for the determination of zooplankton grazing

    NARCIS (Netherlands)

    Lürling, M.F.L.L.W.; Verschoor, A.M.

    2003-01-01

    In the PHYTO-PAM phytoplankton analyzer the minimal fluorescence of dark-adapted samples (F-0) was assessed, which gives direct information on the chlorophyll-a content. Clearance rates (CR) of Daphnia and Brachionus were calculated from a decrease in chlorophyll-a concentration using the PHYTO-PAM

  12. FO-spectra of chlorophyll fluorescence for the determination of zooplankton grazing

    NARCIS (Netherlands)

    Lürling, M.; Verschoor, A.M.

    2003-01-01

    In the PHYTO-PAM phytoplankton analyzer the minimal fluorescence of dark-adapted samples (F0) was assessed, which gives direct information on the chlorophyll- a content. Clearance rates (CR) of Daphnia and Brachionus were calculated from a decrease in chlorophyll-a concentration using the PHYTO-PAM

  13. Protein immobilization and fluorescence quenching on polydopamine thin films.

    Science.gov (United States)

    Chen, Daqun; Zhao, Lei; Hu, Weihua

    2016-09-01

    Mussel inspired polydopamine (PDA) film has attracted great interest as a versatile functional coating for biomolecule immobilization in various bio-related devices. However, the details regarding the interaction between a protein and PDA film remain unclear. Particularly, there is very limited knowledge regarding the protein immobilization on PDA film, even though it is of essential importance in various fields. The situation is even more complicated if considering the fact that quite a number of approaches (e.g., different oxidizing reagent, buffer pH, grown time, grown media, etc.) have been developed to grow PDA films. In this work, protein attachment on PDA film was systematically investigated by using the real-time and label-free surface plasmon resonance (SPR) technique. The kinetics of protein-PDA interaction was explored and the influence of buffer pH and deposition media on the protein attachment was studied. Fluorescent protein microarray was further printed on PDA-coated glass slides for quantitative investigations and together with SPR data, the interesting fluorescence quenching phenomenon of PDA film was revealed. This work may deepen our understanding on the PDA-protein interaction and offer a valuable guide for efficient protein attachment on PDA film in various bio-related applications.

  14. Time-domain imaging with quench-based fluorescent contrast agents

    Science.gov (United States)

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

    2012-03-01

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

  15. A new relative referencing method for crop monitoring using chlorophyll fluorescence

    Science.gov (United States)

    Norikane, J.; Goto, E.; Kurata, K.; Takakura, T.

    The measurement of plant chlorophyll fluorescence has been used for many years as a method to monitor a plant's health status. These types of methods have been mostly relegated to the laboratory. The newly developed Relative Referencing Method allows for the measurement of chlorophyll fluorescence under artificial lighting conditions. The fluorescence signal can be determined by first taking a reference signal measurement, then a second measurement with an additional fluorescence excitation source. The first signal can then be subtracted from the second and the plant's chlorophyll fluorescence due to the second lighting source can be determined. With this simple approach, a photosynthesizing plant can be monitored to detect signs of water stress. Using this approach experiments on tomato plants have shown that it was possible to detect water stress, while the plants were continuously illuminated by fluorescent lamps. This method is a promising tool for the remote monitoring of crops grown in a CELSS-type application.

  16. Overview of Global Monitoring of Terrestrial Chlorophyll Fluorescence from Space

    Science.gov (United States)

    Guanter, Luis; Zhang, Yongguang; Kohler, Philipp; Walther, Sophia; Frankenberg, Christian; Joiner, Joanna

    2016-01-01

    Despite the critical importance of photosynthesis for the Earth system, understanding how it is influenced by factors such as climate variability, disturbance history, and water or nutrient availability remains a challenge because of the complex interactions and the lack of GPP measurements at various temporal and spatial scales. Space observations of the sun-induced chlorophyll fluorescence (SIF) electromagnetic signal emitted by plants in the 650-850nm spectral range hold the promise of providing a new view of vegetation photosynthesis on a global basis. Global retrievals of SIF from space have recently been achieved from a number of spaceborne spectrometers originally intended for atmospheric research. Despite not having been designed for land applications, such instruments have turned out to provide the necessary spectral and radiometric sensitivity for SIF retrieval from space. The first global measurements of SIF were achieved in 2011 from spectra acquired by the Japanese GOSAT mission launched in 2009. The retrieval takes advantage of the high spectral resolution provided by GOSATs Fourier Transform Spectrometer (FTS) which allows the evaluation of the in-filling of solar Fraunhofer lines by SIF. Unfortunately, GOSAT only provides a sparse spatial sampling with individual soundings separated by several hundred kilometers. Complementary, the Global Ozone Monitoring Experiment-2 (GOME-2) instruments onboard MetOp-A and MetOp-B enable SIF retrievals since 2007 with a continuous and global spatial coverage. GOME-2 measures in the red and near-infrared (NIR) spectral regions with a spectral resolution of 0.5 nm and a pixel size of up to 40x40 km2. Most recently, another global and spatially continuous data set of SIF retrievals at 740 nm spanning the 2003-2012 time frame has been produced from ENVISATSCIAMACHY. This observational scenario has been completed by the first fluorescence data from the NASA-JPL OCO-2 mission (launched in July 2014) and the upcoming

  17. Photosynthetic properties of spring geophytes assessed by chlorophyll fluorescence analysis.

    Science.gov (United States)

    Recchia, Irene; Sparla, Francesca; Pupillo, Paolo

    2017-09-01

    Since spring ephemerals are credited to be all "sun" species with unusually elevate photosynthesis, in contrast to shade-tolerant trees and understory geophytes with a long aboveground cycle, we examined the photosynthetic efficiency of 6 woody species, 9 long-cycle geophytes, and 8 spring ephemeral geophytes using blue flashes of increasing energy with the Imaging PAM fluorometer. Several parameters were obtained: quantum yield of electron transport (ΦETR) or of PSII (ΦPSII), maximum measured photosynthesis rate (ETRhv), maximum extrapolated rate of photosynthesis (ETRem), half-saturating photon flux density (KPAR), and in some cases photochemical (qP) and non-photochemical quenching (NPQ). Results confirm the ecological consistency of the three plant groups, with internal differences. Woody species have low ETRem and KPAR values with good ΦETR; long-cycle herbs have low ETRem and ΦETR and moderate KPAR values; spring ephemerals have elevate ΦETR, ETRem and KPAR values. The mean ETRem of ephemerals of 91 μmol m(-2) s(-1) exceeds that of long-cycle herbs 2.9-fold and woody species 4.8-fold, and corresponds to 19 μmol CO2 m(-2) s(-1) by assuming an ETR/ΦCO2 ratio of 4.7. Highest photosynthesis rates and KPAR were exhibited by five ephemerals (Eranthis, Erythronium, Narcissus, Scilla, Tulipa) with peak ETRem values equivalent to ∼40 μmol CO2 m(-2) s(-1) or ∼60 μmol CO2 (g Chl)(-1) s(-1) ("sun" species). According to a new, fluorescence based heliophily index, all trees and five long-cycle herbs were definitely "shade" species, while four long-cycle herbs and three ephemerals were intermediate shade-tolerant. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  18. Spectral and physiological information from chlorophyll fluorescence signals in the detection of pine damage

    Energy Technology Data Exchange (ETDEWEB)

    Meinander, O. [Finnish Meteorological Inst., Helsinki (Finland). Air Quality Dept.; Somersalo, S. [Helsinki Univ., Helsinki (Finland). Dept. of Plant Biology

    1995-12-31

    Photosynthesis is often among the first targets of the air pollution stress of plants. As chlorophyll fluorescence is a process competing with photosynthetic electron transport it can be employed to study the potential photosynthetic capacity and to detect damage to the photosynthetic apparatus. Many previous studies have shown that chlorophyll fluorescence can be a powerful tool in the detection of forest damage. In this preliminary study, singular value analysis of the fluorescence induction curves was used together with the traditional way of analyzing fluorescence measurements. The experimental data were collected from ozone and carbon dioxide fumigated Scots pine saplings. (author)

  19. Effects of water stress and light intensity on chlorophyll fluorescence parameters and pigments of Aloe vera L.

    Science.gov (United States)

    Hazrati, Saeid; Tahmasebi-Sarvestani, Zeinolabedin; Modarres-Sanavy, Seyed Ali Mohammad; Mokhtassi-Bidgoli, Ali; Nicola, Silvana

    2016-09-01

    Aloe vera L. is one of the most important medicinal plants in the world. In order to determine the effects of light intensity and water deficit stress on chlorophyll (Chl) fluorescence and pigments of A. vera, a split-plot in time experiment was laid out in a randomized complete block design with four replications in a research greenhouse. The factorial combination of three light intensities (50, 75 and 100% of sunlight) and four irrigation regimes (irrigation after depleting 20, 40, 60 and 80% of soil water content) were considered as main factors. Sampling time was considered as sub factor. The first, second and third samplings were performed 90, 180 and 270 days after imposing the treatments, respectively. The results demonstrated that the highest light intensity and the severe water stress decreased maximum fluorescence (Fm), variable fluorescence (Fv)/Fm, quantum yield of PSII photochemistry (ФPSII), Chl and photochemical quenching (qP) but increased non-photochemical quenching (NPQ), minimum fluorescence (F0) and Anthocyanin (Anth). Additionally, the highest Fm, Fv/Fm, ФPSII and qP and the lowest NPQ and F0 were observed when 50% of sunlight was blocked and irrigation was done after 40% soil water depletion. Irradiance of full sunlight and water deficit stress let to the photoinhibition of photosynthesis, as indicated by a reduced quantum yield of PSII, ФPSII, and qP, as well as higher NPQ. Thus, chlorophyll florescence measurements provide valuable physiological data. Close to half of total solar radiation and irrigation after depleting 40% of soil water content were selected as the most efficient treatments.

  20. Detection of Fluorescence from Single Chlorophyll a Molecules Absorbed on Glass Surface

    Institute of Scientific and Technical Information of China (English)

    JI Dong-Mei; HUANG Zheng-Xi; XIA An-Dong

    2005-01-01

    @@ We investigate the single molecule spectroscopy of chlorophyll a molecules on glass surface in N2-saturated environment. The basic photodynamic parameters of chlorophyll a molecules, such as fluorescence lifetime,survival time before photobleaching, on-time, and off-time, are reported. A four-level model is employed to describe the possible dynamics and photobleaching of chlorophyll a upon excitation. Broad distributions in fluorescence lifetimes and survival times are mainly due to the heterogeneities of both molecular conformation and local environment.

  1. Determination of epristeride by its quenching effect on the fluorescence of L-tryptophan

    Institute of Scientific and Technical Information of China (English)

    Ai-Qin Gong; Xia-Shi Zhu

    2013-01-01

    A rapid, novel spectrofluorimetric method to determine epristeride (EP) in biological fluids and a pharmaceutical formulation was developed, based on the fact that fluorescence intensity of L-tryptophan could be quenched by EP in the medium of pH ¼ 9.0. The various factors influencing fluorescence quenching were discussed. The quenching mechanism was investigated with the quenching type, synchronous fluorescence spectra and quantum efficiency. Under the optimized conditions, fluorescence quenching value (ΔF ¼ FL-tryptophan-FEP-L-tryptophan) showed a good linear relationship with the EP concentration ranging from 0.4 to 12.0μg/mL. The linearity, recovery and limit of detection demonstrated that the proposed method was suitable for EP determination in biological fluids and EP tablets. The method was successfully applied to the analysis of EP in real samples and the obtained results were in good agreement with the results of the official method.

  2. Aspect ratio dependent fluorescence quenching of eosin Y by gold nanorods.

    Science.gov (United States)

    Weng, Guojun; Li, Jianjun; Zhang, Li; Zhao, Junwu

    2014-06-01

    Gold nanorods of different aspect ratios had been synthesized using seed mediated growth method. The formed gold nanorods had been characterized by the absorption and transmission electron microscopy (TEM) measurements. The obtained gold nanorods were used to study the quenched effect on fluorescence of Eosin Y. Experimental results revealed that Eosin Y molecules adsorbed on the metallic surfaces, suffering strong quenching of their fluorescence and the quenching efficiency was different for different aspect ratio. Using dielectric coated gold nanorods model, the probable mechanism of aspect ratio dependent quenching efficiency was obtained by numerical calculation based on fluorescence resonance energy transfer and quasi-static theory. The calculation results showed that the non-monotonic changing of fluorescence quenching was attributed to competing effects of aspect ratio and the dielectric constant of coated shell on surface plasmon resonance.

  3. Assay of ceftazidime and cefepime based on fluorescence quenching of carbon quantum dots.

    Science.gov (United States)

    Huang, Yu; Zhang, Ying; Yan, Zhengyu; Liao, Shenghua

    2015-11-01

    A novel and sensitive method for the determination of ceftazidime and cefepime in an active pharmaceutical ingredient (API) has been developed based on the fluorescence quenching of poly(ethylene glycol) (PEG)2000-capped carbon quantum dots (CQDs) prepared using a chemical oxidation method. The quenching of fluorescence intensity is proportional to the concentration of ceftazidime and cefepime over the range of 0.33-3.30 and 0.24-2.40 µg/mL, respectively. The mode of interaction between PEG2000-capped CQDs and ceftazidime/cefepime in aqueous solutions was investigated using a fluorescence, UV/Vis and Fourier transform infrared spectrometry (FTIR) at physiological pH. UV/Vis and FTIR spectra demonstrated that ground state compounds were formed through hydrophobic interaction the fluorescence quenching of CQDs caused by ceftazidime and cefepime. The quenching constants decreased with increases in temperature, which was consistent with static quenching.

  4. Short-duration exposure to radiofrequency electromagnetic radiation alters the chlorophyll fluorescence of duckweeds (Lemna minor).

    Science.gov (United States)

    Senavirathna, Mudalige Don Hiranya Jayasanka; Takashi, Asaeda; Kimura, Yuichi

    2014-12-01

    Plants growing in natural environments are exposed to radiofrequency electromagnetic radiation (EMR) emitted by various communication network base stations. The environmental concentration of this radiation is increasing rapidly with the congested deployment of base stations. Although numerous scientific studies have been conducted to investigate the effects of EMR on the physiology of humans and animals, there have been few attempts to investigate the effects of EMR on plants. In this study, we attempted to evaluate the effects of EMR on photosynthesis by investigating the chlorophyll fluorescence (ChF) parameters of duckweed fronds. During the experiment, the fronds were tested with 2, 2.5, 3.5, 5.5 and 8 GHz EMR frequencies, which are not widely studied even though there is a potentially large concentration of these frequencies in the environment. The duckweed fronds were exposed to EMR for 30 min, 1 h and 24 h durations with electric field strength of 45-50 V/m for each frequency. The results indicated that exposure to EMR causes a change in the non-photochemical quenching of the duckweeds. The changes varied with the frequency of the EMR and were time-varying within a particular frequency. The temperature remained unchanged in the duckweed fronds upon exposure to EMR, which confirms that the effect is non-thermal.

  5. CO2 Exchange and Chlorophyll Fluorescence of Phosphoenolpyruvate Carboxylase Transgenic Rice Pollen Lines

    Institute of Scientific and Technical Information of China (English)

    Li-Li Ling; Hong-Hui Lin; Ben-Hua Ji; De-Mao Jiao

    2006-01-01

    To elucidate the photosynthetic physiological characteristics and the physiological inherited traits of rice(Oryza sativa L.) hybrids and their parents, physiological indices of photosynthetic CO2 exchange and chlorophyll fluorescence parameters were measured in leaves of the maize phosphoenolpyruvate carboxylase (PEPC) transgenic rice as the male parent, sp. japonica rice cv. 9516 as the female parent, and the stable JAAS45 pollen line. The results revealed that the PEPC gene could be stably inherited and transferred from the male parent to the JAAS45 pollen line. Moreover, the JAAS45 pollen line exhibited high levels of PEPC activity, manifesting higher saturated photosynthetic rates, photosynthetic apparent quantum yield (AQY), photochemical efficiency of photosystem Ⅱ and photochemical and non-photochemical quenching, which indicated that the JAAS45 pollen line has a high tolerance to photo-inhibition/photooxidation under strong light and high temperature. Furthermore, JAAS45 was confirmed to still be a C3 plant by δ13C carbon isotope determination and was demonstrated to have a limited photosynthetic C4 microcycle by feeding with exogenous C4 primary products, such as oxaloacetate or maiate, or phosphoenolpyruvate.The present study explains the physiological inherited properties of PEPC transgenic rice and provides an expectation for the integration of traditional breeding and biological technology.

  6. Fluorescence Quenching Study of Zinc Bisporphyrins by Fulleropyrrolidines and Their N-Oxides

    Institute of Scientific and Technical Information of China (English)

    XU Hua; YANG Yi; ZHU Yi-Zhou; ZHENG Jian-Yu

    2006-01-01

    Novel phenylene-bridged zinc bisporphyrins (1-4), fulleropyrrolidines (C60-m, C60-h) and their N-oxides C6o-mo, C60-ho) were synthesized. The fluorescence quenching processes of bisporphyrins in toluene solution by fulleropyrrolidines and their N-oxides were investigated by steady-state fluorescence spectra. The fluorescence quenching constants proved that the fluorescence quenching ability was decreased as reduction of thepyrrolidinefunctionalgroups of fullerene surface: C60-h>C60-m>C60, and the fluorescence quenching ability was increased about 1.3-7.4 times by utilizing fulleropyrrolidine N-oxides (C60-mo, C60-ho) compared to fulleropyrrolidine compounds (C60-m, C60-h). The results revealed photoinduced electron transfer (PET) efficiencybetweenbisporphyrinandfullerenederivativescould be tunable by change of functional groups on fullerene surface.

  7. Interaction of potassium mono and di phosphates with bovine serum albumin studied by fluorescence quenching method.

    Science.gov (United States)

    Bakkialakshmi, S; Shanthi, B; Chandrakala, D

    2011-03-01

    The interactions between potassium mono and di phosphates and bovine serum albumin (BSA) were studied using fluorescence spectroscopy (FS) and ultraviolet spectroscopy (UV). The experimental results showed that the potassium mono and di phosphates could insert into the BSA and quench the inner fluorescence of BSA by forming the potassium mono phosphate-BSA and pottassium di phosphate-BSA complexes. It was found that the static quenching was the main reason leading to the fluorescence quenching. It was conformed by XRD and SEM techniques.

  8. Relationships between the photochemical reflectance index (PRI) and chlorophyll fluorescence parameters and plant pigment indices at different leaf growth stages.

    Science.gov (United States)

    Rahimzadeh-Bajgiran, Parinaz; Munehiro, Masashi; Omasa, Kenji

    2012-09-01

    This study aimed to evaluate the photochemical reflectance index (PRI) for assessing plant photosynthetic performance throughout the plant life cycle. The relationships between PRI, chlorophyll fluorescence parameters, and leaf pigment indices in Solanum melongena L. (aubergine; eggplant) were studied using photosynthetic induction curves both in short-term (diurnal) and long-term (seasonal) periods under different light intensities. We found good correlations between PRI/non-photochemical quenching (NPQ) and PRI/electron transport rate (ETR) in the short term at the same site of a single leaf but these relationships did not hold throughout the life of the plant. In general, changes in PRI owing to NPQ or ETR variations in the short term were PRI was highly correlated to plant pigments, especially chlorophyll indices measured by spectral reflectance. Moreover, relationships of steady-state PRI/ETR and steady-state PRI/photochemical yield of photosystem II (Φ(PSII)) measured at uniform light intensity at different life stages proved that overall photosynthesis capacity and steady-state PRI were better correlated through chlorophyll content than NPQ and xanthophylls. The calibrated PRI index accommodated these pigments effects and gave better correlation with NPQ and ETR than PRI. Further studies of PRI indices based on pigments other than xanthophylls, and studies on PRI mechanisms in different species are recommended.

  9. Two-photon excited fluorescence from higher electronic states of chlorophylls in photosynthetic antenna complexes a new approach to detect strong excitonic chlorophyll a/b coupling

    CERN Document Server

    Leupold, D; Ehlert, J; Irrgang, K D; Renger, G; Lokstein, H

    2002-01-01

    Stepwise two-photon excitation of chlorophyll a and b in the higher plant main light-harvesting complex (LHC II) and the minor complex CP29 (as well as in organic solution) with 100-fs pulses in the Q/sub y/ region results in a weak blue fluorescence. The dependence of the spectral shape of the blue fluorescence on excitation wavelength offers a new approach to elucidate the long-standing problem of the origin of spectral "chlorophyll forms" in pigment-protein complexes, in particular the characterization of chlorophyll a/b-heterodimers. As a first result we present evidence for the existence of strong chlorophyll a/b-interactions (excitonically coupled transitions at 650 and 680 nm) in LHC II at ambient temperature. In comparison with LHC II, the experiments with CP29 provide further evidence that the lowest energy chlorophyll a transition (at ~680 nm) is not excitonically coupled to chlorophyll b. (22 refs).

  10. [A fluorescence quenching method for the determination of trace chlorite in water with rhodamine B].

    Science.gov (United States)

    Kang, Cai-yan; Jiang, Zhi-liang; Xi, Dan-li

    2007-02-01

    In acidic sodium acetate-HCl buffer solution containing KI, Rhodamine B (RhB) has a fluorescence peak at 580 nm. When ClO2(-) exists fluorescence quenching occur. The fluorescence quenching intensity is linear with the concentration of ClO2(-) in the range of 0.0218-0.51 microg x mL(-1). Based on this, a new, simple, sentisive fluorescence method has been proposed for the determination of ClO2(-) in water, with satisfactory results.

  11. Fluorescence quenching behaviour of uric acid interacting with water-soluble cationic porphyrin

    Energy Technology Data Exchange (ETDEWEB)

    Makarska-Bialokoz, Magdalena, E-mail: makarska@hektor.umcs.lublin.pl [Department of Inorganic Chemistry, Maria Curie-Sklodowska University M. C. Sklodowska Sq. 2, 20-031 Lublin (Poland); Borowski, Piotr [Faculty of Chemistry, Maria Curie-Sklodowska University M. C. Sklodowska Sq. 3, 20-031 Lublin (Poland)

    2015-04-15

    The process of association between 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H{sub 2}TTMePP) and uric acid as well as its sodium salt has been studied in aqueous NaOH solution analysing its absorption and steady-state fluorescence spectra. The fluorescence quenching effect observed during interactions porphyrin-uric acid compounds points at the fractional accessibility of the fluorophore for the quencher. The association and fluorescence quenching constants are of the order of magnitude of 10{sup 5} mol{sup −1}. The fluorescence lifetimes and the quantum yields of the porphyrin anionic form were established. The results demonstrate that uric acid and its sodium salt can interact with H{sub 2}TTMePP at basic pH and through formation of stacking complexes are able to quench its ability to emission. - Highlights: • Association study of water soluble cationic porphyrin with uric acid. • Porphyrin absorption spectra undergo the bathochromic and hypochromic effects. • Uric acid interacts with porphyrin in inhibiting manner, quenching its emission. • Fluorescence quenching effect testifies for the partial inactivation of a porphyrin. • The association and fluorescence quenching constants were calculated.

  12. Fluorescence quenching of fluoroquinolone antibiotics by 4-hydroxy-TEMPO in aqueous solution.

    Science.gov (United States)

    Żamojć, Krzysztof; Wiczk, Wiesław; Zaborowski, Bartłomiej; Makowski, Mariusz; Pranczk, Joanna; Jacewicz, Dagmara; Chmurzyński, Lech

    2014-12-10

    The fluorescence quenching of norfloxacin, danofloxacin, enrofloxacin and levofloxacin, belonging to a group of fluoroquinolone antibiotics, by 4-hydroxy-TEMPO was studied in aqueous solutions with the use of steady-state, time-resolved fluorescence spectroscopy as well as UV-VIS absorption spectroscopy methods. In order to understand the mechanism of quenching the absorption and fluorescence emission spectra of all fluoroquinolone antibiotics studied as well as decreases of their fluorescence were registered as a function of the 4-hydroxy-TEMPO concentration. No deviations from a linearity in the Stern-Volmer plots (determined from both, steady-state and time-resolved measurements) were observed. The fluorescence quenching mechanism was proved to be totally dynamic, what was additionally confirmed by the registration of Stern-Volmer plots at 5 temperatures ranging from 15 to 55°C. On the basis of theoretical calculations of fluoroquinolones' molecular radii and ionization potentials the mechanism of electron transfer was rejected. It seems that the fluorescence quenching is diffusion-limited and is caused by the increase of nonradiative processes, such as internal conversion or intersystem crossing. The Stern-Volmer quenching constants and bimolecular quenching constants were determined at the room temperature for all fluoroquinolone antibiotics studied. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Effect of Phosphatidylcholine on the Steady State Fluorescence of Chlorophyll in Photosystem Ⅱ Particles

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Phosphatidylcholine (PC) accounts for less than 1% of the total lipids in plant photosystem II (PSII) particles.In this experiment, PSII particles were reconstituted with PC to construct PSII-PC vesicles.The effect of PC on the steady state fluorescence of chlorophyll (Chl) in PSII particles was studied.The results show that PC significantly affected the fluorescence intensity, but did not obviously affect the fluorescence emission band peak position.PC also did not obviously affect the absorbance at 436 nm or the amide I band peak position in FT-IR spectroscopy of PSII particles.The results suggest that PC may affect the light energy transfer from the antenna chlorophyll molecules to the reaction center chlorophyll molecule (P680).

  14. ZnSe quantum dots based fluorescence quenching method for determination of paeoniflorin

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhi [Center of Analysis, Guangdong Medical College, Dongguan 523808 (China); School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China); Chen, Jiayi; Liang, Qiaowen [School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China); Wu, Dudu [Center of Analysis, Guangdong Medical College, Dongguan 523808 (China); Zeng, Yuaner, E-mail: zengyuaner@126.com [School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China); Jiang, Bin, E-mail: gzjiangbin@hotmail.com [School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China)

    2014-01-15

    Water soluble ZnSe quantum dots (QDs) modified by mercaptoacetic acid (MAA) were used to determinate paeoniflorin in aqueous solutions by the fluorescence spectroscopic technique. The results showed that the fluorescence of the modified ZnSe QDs could be quenched by paeoniflorin effectively in physiological buffer solution. The optimum fluorescence intensity was found to be at incubation time 10 min, pH 7.0 and temperature 25 °C. Under the optimal conditions, the detection limit of paeoniflorin was 7.30×10{sup −7} mol L{sup −1}. Moreover, the quenching mechanism was discussed to be a static quenching procedure, which was proved by quenching rate constant K{sub q} (1.02×10{sup 13} L mol{sup −1} s{sup −1}). -- Highlights: • The fluorescence intensity of ZnSe QDs could be quenched by paeoniflorin. • Foreign substance showed insignificant effect for determination of paeoniflorin. • The quenching mechanism was discussed to be a static quenching procedure.

  15. Halide (Cl(super -)) Quenching of Quinine Sulfate Fluorescence: A Time-Resolved Fluorescence Experiment for Physical Chemistry

    Science.gov (United States)

    Gutow, Jonathan H.

    2005-01-01

    The time-resolved fluorescence experiment investigating the halide quenching of fluorescence from quinine sulfate in water is described. The objectives of the experiment include reinforcing student understanding of the kinetics of competing pathways, making connections with microscopic theories of kinetics through comparison of experimental and…

  16. Chlorophyll Fluorescence Is a Better Proxy for Sunlit Leaf Than Total Canopy Photosynthesis

    Science.gov (United States)

    Chen, J. M.; Wang, Z.; Zhang, F.; Mo, G.

    2015-12-01

    Chlorophyll fluorescence (CF) results from non-photochemical quenching during plant photosynthesis under excessive radiation. We explore the relationship between gross primary productivity (GPP) and CF using a process ecosystem model, which separates a vegetation canopy into sunlit and shaded leaf groups and simulates the total canopy GPP as the sum of sunlit and shaded leaf GPP. Using GOME-2 and GOSAT data acquired in 2010 over the global land surface, we found that measured CF signals gridded in 1 degree resolution are well correlated with simulated total GPP and its sunlit and shaded components, but the correlation coefficients (R) are largest for the sunlit GPP and smallest for shaded GPP. The seasonal R2 values vary from 0.57 to 0.74, 0.58 to 0.71, and 0.48 to 0.56 for sunlit, total and shaded GPP, respectively. The significance levels for these correlations are all greater than pCASA model results, respectively. These values are similar or larger than those for sunlit GPP simulated in our study, but are considerably larger than those for total GPP in our study because the correlation for total GPP is contaminated by the inclusion of shaded GPP. All these three models use canopy total light use efficiency without considering the differences between sunlit and shaded leaves, and therefore they mostly capture spatio-temporal variations in sunlit GPP. We therefore argue that solar-induced CF measured from vegetation is a better proxy of sunlit GPP than the total GPP, and the use of CF data for assessing the terrestrial carbon cycle can be improved when sunlit and shaded GPP are modelled separately.

  17. New algorithm for MODIS chlorophyll fluorescence height retrieval: performance and comparison with the current product

    Science.gov (United States)

    Ioannou, I.; Zhou, J.; Gilerson, A.; Gross, B.; Moshary, F.; Ahmed, S.

    2009-09-01

    Our previous studies showed that the Fluorescence Line Height (FLH) product, which uses 3 NIR bands at 667, 678, and 746 nm on the MODerate-resolution Imaging Spectroradiometer (MODIS) sensor, and similar bands on MERIS sensor, is not reliable in coastal waters because of a peak in the elastic reflectance spectra which occurs due to the confluence of chlorophyll and water absorption spectra and which overlaps spectrally the chlorophyll fluorescence. This combination of two overlapping peaks makes fluorescence signal retrieval inaccurate. As a consequence, the present FLH algorithm significantly underestimates fluorescence magnitudes in coastal waters. To overcome this problem, we introduce a new and more accurate approach for the retrieval of FLH in turbid waters by the MODIS sensor, which exploits the correlation between the blue-green and red bands reflectance ratios. We show that by making use of the combined remote sensing reflectance's (Rrs) at 488nm, 547nm, 667nm and 678nm we can retrieve fluorescence accurately in case 2 waters even for low fluorescence quantum yield when fluorescence magnitudes are low. The derivation and validation of our algorithm was performed using extensive synthetic datasets which cover a large variability of parameters typical of coastal waters: with CDOM absorption at 400nm 0-2 m-1, mineral concentration 0-5g/m3 and chlorophyll concentration of 0.5-100 mg/m3. In addition, we applied this proposed algorithm to MODIS satellite data and compared it with the traditional FLH algorithm.

  18. Fluorescence quenching in luminescent porous silicon nanoparticles for the detection of intracellular Cu2+.

    Science.gov (United States)

    Xia, Bing; Zhang, Wenyi; Shi, Jisen; Xiao, Shoujun

    2013-07-01

    After microwave-induced hydrosilylation reaction with 10-undecenoic acid, luminescent porous silicon nanoparticles (LPSiNPs) showed excellent fluorescence stability under physiological conditions. Fluorescence quenching in as-prepared LPSiNPs was highly sensitive with the concentration of Cu(2+) at μmol L(-1) level, which could be further applied to the detection of intracellular Cu(2+).

  19. Binding Interaction of Captopril with Metal Ions: A Fluorescence Quenching Study

    Institute of Scientific and Technical Information of China (English)

    SIDDIQI K.S.; BANO Shaista; MOHD Ayaz; KHAN Aslam Aftab Parwaz

    2009-01-01

    The binding interaction of captopril(CPL)with biologically active metal ions Mg2+,Ca2+,Mn2+,Co2+,Ni2+,Cu2+ and Zn2+ was investigated in an aqueous acidic medium by fluorescence spectroscopy.The experimental results showed that the metal ions quenched the intrinsic fluorescence of CPL by forming CPL-metal complexes.It was found that static quenching was the main reason for the fluorescence quenching.The quenching constant in the case of Cu2+ was highest among all quenchers,perhaps due to its high nuclear charge and small size.Quenching of CPL by metal ions follows the order Cu2+> Ni2+> Co2+> Ca2+>Zn2+ > Mn2+ > Mg2+.The quenching constant Ksv,bimolecular quenching constant Kq,binding constant K and the binding sites "n" were determined together with their thermodynamic parameters at 27 and 37℃.The positive entropy change indicated the gain in configurational entropy as a result of chelation.The process of interaction was spontaneous and mainly △S-driven.

  20. The fluorescence quenching and resonance Rayleigh scattering enhancement of ET-CPM system

    Institute of Scientific and Technical Information of China (English)

    YANG JiDong; ZHOU Shang

    2009-01-01

    In pH 4.4 BR buffer medium, erythrosine (ET) and Chlorphensmine Maleate (CPM) could form ion-as-sociation complex, which led to the quenching of fluorescence and synchronous fluorescence, and the significant enhancement of resonance Rayleigh scattering(RRS) of erythrosine. Furthermore, a new RRS spectrum would appear, and the maximum RRS wavelength was located at about 578 rim. The quenched fluorescence and enhanced RRS intensity was directly proportional to the concentration of CPM in the ranges of 0.24-8.0 μg/mL, and 0.008-3.6 μg/mL, respectively. The method has been ap-plied to determine CPM in urine samples with satisfactory results. The mechanisms of the RRS en-hancement and fluorescence quenching were discussed as well.

  1. The equal-efficiency-proving of fluorescence quenching and enhancement equation

    Institute of Scientific and Technical Information of China (English)

    YANG Manman; XI Xiaoli; YANG Pin

    2005-01-01

    Through the fluorescence and ultravioletvisible spectrophotometry we have studied the action of cefoperazone sodium and worfloxacin, two kinds of medicinewith albumin, and examined the equal efficiency quality offluorescence enhancement and fluorescence quenching equation. The result shows the equal efficiency of calculating dissociation constant. In this article, we obtain the dissociationconstants of the action of the two kinds of medicine with bovine serum albumin, energy- transfer efficiency, the distanceof donor-acceptor and quenching constants. The above showsthat the action is not caused by dynamic collision but by thebinding of medicine and albumin. This article speciallypoints out that the [Mt]/[Pt], which is the ratio of the maximum mol concentration of the quenching agent (medicine) tofluorescent (albumin) mol concentration when the quenchingends, is very important because it is the maximum bindingnumber of quenching agent molecule to a fluorescent molecule. There is no more quenching after adding more quenching agent beyond this quantity to fluorescent solution. Thisquantity is determined directly and strictly by experiment, sois also of important significance when discussing quenchingefficiency and binding situation of donor-acceptor.

  2. Modeling the impact of spectral sensor configurations on the FLD retrieval accuracy of sun-induced chlorophyll fluorescence

    NARCIS (Netherlands)

    Damm, A.; Erler, A.; Hillen, W.; Meroni, M.; Schaepman, M.E.; Verhoef, W.; Rascher, U.

    2011-01-01

    Chlorophyll fluorescence is related to photosynthesis and can serve as a remote sensing proxy for estimating photosynthetic energy conversion and carbon uptake. Recent advances in sensor technology allow remote measurements of the sun-induced chlorophyll fluorescence signal (Fs) at leaf and canopy s

  3. Behavior of Sethoxydim Alone or in Combination with Turnip Oils on Chlorophyll Fluorescence Parameter

    Directory of Open Access Journals (Sweden)

    Hossein HAMMAMI

    2014-03-01

    Full Text Available Sethoxydim is an acetyl-coenzyme A carboxylase (ACCase inhibitor that changed the shape of the chlorophyll fluorescence curve (kautsky curve in wild oat (Avena ludoviciana Durieu. in greenhouse experiment. This experiment was conducted as completely randomized factorial design with three replications at the College of Agriculture, Ferdowsi University of Mashhad, Iran, during 2012. Results of this study revealed that sethoxydim only and plus emulsifiable turnip oil changed the shape of the chlorophyll fluorescence curve (kautsky curve 7 days after spraying. Sethoxydim plus emulsifiable turnip oil changed the shape of the kautsky curve more than for sethoxydim only. We found that in our study the fv/fm (maximum quantum efficiency was closely linked to the fresh and dry weight dose-response. Sethoxydim plus emulsifiable turnip oil proved more rapidly effect on fv/fm in comparison with sethoxydim only. The fresh and dry weight dose-response relationship with fv/fm showed a similar behavior. This study revealed a good relation between fresh and dry weight according with values of 28 DAS and fv/fm 7 DAS. In general, the findings of this study revealed that Fv/Fm is a good parameter for evaluating effect of sethoxydim little time after spraying. Also, this research showed that 4 folds more time for classical screening methods comparing to chlorophyll fluorescence method. Thereupon, classical screening methods may be replaced by chlorophyll fluorescence method in future.

  4. Spatial heterogeneity in active chlorophyll fluorescence and PSII activity of coral tissues

    DEFF Research Database (Denmark)

    Ralph, P.J.; Gademann, R.; Larkum, A.W.D.

    2002-01-01

    Chlorophyll-a fluorescence was measured in six species of coral, using pulse-amplitude-modulated fluorometers employing fibre-optic probes with diameters of 8 mm, 1 mm and 140 µm. The 8-mm probe integrated responses over a large area, giving more weight to coenosarc than polyp tissue for Acropora...

  5. Chlorophyll fluorescence varies more across seasons than leaf water potential in drought-prone plants

    Directory of Open Access Journals (Sweden)

    BRUNO H.P. ROSADO

    2016-01-01

    Full Text Available ABSTRACT Among the effects of environmental change, the intensification of drought events is noteworthy, and tropical vegetation is predicted to be highly vulnerable to it. However, it is not clear how tropical plants in drought-prone habitats will respond to this change. In a coastal sandy plain environment, we evaluated the response of six plant species to water deficits across seasons, the relationship between their morpho-physiological traits, and which traits would be the best descriptors of plants' response to drought. Regardless of leaf succulence and phenology, responses between seasons were most strongly related to chlorophyll fluorescence. In this study we have demonstrated that a better comprehension of how tropical species from drought-prone habitats cope with changes in water availability can be based on seasonal variation in leaf water potential and chlorophyll fluorescence. Temporal variation in leaf water potential and chlorophyll fluorescence was found useful for differentiating between groups of sandy soil species that are responsive or unresponsive to water availability. However, chlorophyll fluorescence appeared to be a more sensitive descriptor of their seasonal and short-term responses.

  6. Interregional difference in spring neap variations in stratification and chlorophyll fluorescence during summer in a tidal sea (Yatsushiro Sea, Japan)

    Science.gov (United States)

    Aoki, Kazuhiro; Onitsuka, Goh; Shimizu, Manabu; Matsuo, Hitoshi; Kitadai, Yuuki; Ochiai, Hironori; Yamamoto, Takeshi; Furukawa, Shinpei

    2016-10-01

    Spring neap variations in stratification and chlorophyll fluorescence were studied during the summers of 2011-2014 in a tidal sea (Yatsushiro Sea, Japan) using monitoring data and hydrodynamic models. Vertical profiles of salinity, temperature and chlorophyll fluorescence were collected nearly weekly from nine stations in this sea during the same period. Composite analysis using vertical profiles of density clearly indicated enhancement of the stratification during the neap tide and a vertically mixed water column during the spring tide in the tidal area. Interregional differences were revealed in the variation of chlorophyll fluorescence with the spring neap tidal cycle. More notable increases in chlorophyll fluorescence were observed during the neap tide in the tidal area around the narrow strait than in the inner area. Temporal stratification led to an increase in the chlorophyll fluorescence in the tidal strait during the neap tide.

  7. Metal-enhanced fluorescence of chlorophylls in light-harvesting complexes coupled to silver nanowires.

    Science.gov (United States)

    Kowalska, Dorota; Krajnik, Bartosz; Olejnik, Maria; Twardowska, Magdalena; Czechowski, Nikodem; Hofmann, Eckhard; Mackowski, Sebastian

    2013-01-01

    We investigate metal-enhanced fluorescence of peridinin-chlorophyll protein coupled to silver nanowires using optical microscopy combined with spectrally and time-resolved fluorescence techniques. In particular we study two different sample geometries: first, in which the light-harvesting complexes are deposited onto silver nanowires, and second, where solution of both nanostructures are mixed prior deposition on a substrate. The results indicate that for the peridinin-chlorophyll complexes placed in the vicinity of the silver nanowires we observe higher intensities of fluorescence emission as compared to the reference sample, where no nanowires are present. Enhancement factors estimated for the sample where the light-harvesting complexes are mixed together with the silver nanowires prior deposition on a substrate are generally larger in comparison to the other geometry of a hybrid nanostructure. While fluorescence spectra are identical both in terms of overall shape and maximum wavelength for peridinin-chlorophyll-protein complexes both isolated and coupled to metallic nanostructures, we conclude that interaction with plasmon excitations in the latter remains neutral to the functionality of the biological system. Fluorescence transients measured for the PCP complexes coupled to the silver nanowires indicate shortening of the fluorescence lifetime pointing towards modifications of radiative rate due to plasmonic interactions. Our results can be applied for developing ways to plasmonically control the light-harvesting capability of photosynthetic complexes.

  8. Analysis of fluorescence quenching of coumarin derivatives by 4-hydroxy-TEMPO in aqueous solution.

    Science.gov (United States)

    Żamojć, Krzysztof; Wiczk, Wiesław; Zaborowski, Bartłomiej; Jacewicz, Dagmara; Chmurzyński, Lech

    2014-05-01

    The fluorescence quenching of different coumarin derivatives (7-hydroxy-4-methylcoumarin, 5,7-dimethoxycoumarin, 7-amino-4-methyl-3-coumarinylacetic acid, 7-ethoxy-4-methylcoumarin, 7-methoxycoumarin, 7-hydroxycoumarin, 7-hydroxy-4-methyl-3-coumarinylacetic acid and 7-amino-4-methylcoumarin) by 4-hydroxy-TEMPO in aqueous solutions at the room temperature was studied with the use of UV-Vis absorption spectroscopy as well as a steady-state and time-resolved fluorescence spectroscopy. In order to understand the mechanism of quenching the absorption and fluorescence emission spectra of all coumarins along with fluorescence decays were recorded under the action of 4-hydroxy-TEMPO. The Stern-Volmer plots (both from time-averaged and time-resolved measurements) displayed no positive (upward) deviation from a linearity. The fluorescence quenching mechanism was found to be entirely dynamic, what was additionally confirmed by the registration of Stern-Volmer plots at different temperatures. The Stern-Volmer quenching constants and bimolecular quenching rate constants were obtained for all coumarins studied at the room temperature. The findings demonstrate the possibility of developing an analytical method for the quantitative determination of the free radicals' scavenger, 4-hydroxy-TEMPO.

  9. [Effects of O3-FACE(ozone-free air control enrichment) on gas exchange and chlorophyll fluorescence of rice leaf].

    Science.gov (United States)

    Liang, Jing; Zeng, Qing; Zhu, Jian-Guo; Zhu, Chun-Wu; Cao, Ji-Ling; Xie, Zu-Bin; Liu, Gang; Tang, Hao-Ye

    2010-04-01

    O3-FACE (Ozone-free air control enrichment) platform has been established for observing the effect of elevated tropospheric ozone concentration on the gas exchange and chlorophyll fluorescence of two rice varieties (Wuyunjing 21 and Liangyoupeijiu). The results showed that high ozone concentration decreased the net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) of rice leaves. After 76d fumigation the decline in them for Wuyunjing 21 was as follows: 21.7%, 26.64% and 24.74% respectively, and that for Liangyoupeijiu was as follows: 25.53%, 30.31% and 25.48% respectively; however, no significant impact on leaf intercellular CO2 concentration was observed. Chlorophyll fluorescence kinetics parameters changed as can be seen by the decrease in F0 (initial fluorescence in the dark), ETR (The apparent electron transfer rate) and psiPSII (actual photochemical efficiency of PS II in the light), and the increase in NPQ (non-photochemical quenching). After 76 days of O3 treatment, the NPQ of Wuyunjing 21 and Liangyoupeijiu was enhanced by 16.37% and 11.77%, respectively. The impact of ozone on rice was a cumulative effect, and the extent of variation in the above parameters and the differences between the two varieties were enlarged as the O3 treatment time increased; At the same time because the rice leaf intercellular CO2 concentration did not significantly reduce, the inferred decrease in net photosynthetic rate was restricted by non-stomatal factors. The results of this experiment indicated that Liangyoupeijiu was more susceptible to ozone than Wuyunjing 21.

  10. Effect of Nitrogen Fertilization on Leaf Chlorophyll Fluorescence in Field-Grown Winter Wheat Under Rainfed Conditions

    Institute of Scientific and Technical Information of China (English)

    SHANGGUAN Zhou-ping; ZHENG Shu-xia; ZHANG Lei-ming; XUE Qing-wu

    2005-01-01

    The effect of nitrogen fertilization on leaf chlorophyll fluorescence was studied in field-grown winter wheat during grain filling under rainfed conditions in Loess Plateau. Results showed that the actual photochemical efficiency of PS Ⅱ reaction center (Ф PS Ⅱ) decreased significantly as leaf water stress progressed, however, the Ф PS was increased by nitrogen fertilization. The Ф PS Ⅱ of 0, 90 and 180 kg ha-1 nitrogen treatments at noon were 0.197, 0.279 and 0.283, respectively, which decreased by 57.7, 56.4 and 40.2% as compared was even higher than that in the moming. Application of nitrogen fertilizer significantly increased maximum photochemical efficiency (Fv/Fm), photochemical quenching coefficient (qP) and non-photochemical quenching coefficient (qNP). These results indicated that application of nitrogen fertilizer could increase the light energy conversion efficiency, the potential activity of photosynthetic reaction center, and the non-photochemical dissipation of excess light energy, which can prevent leaf photosynthetic apparatus from damage of treatments, indicating that the excess nitrogen was unfavorable to photosynthesis.

  11. Effects of Chlorophyll Availability on Fluorescence Components of Photosystems in the ORF469-Deletion Mutant of Cyanobacterium

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    PCR-amplified ORF469 fragment from Synechocystis sp.PCC 6803 was cloned into pUC118 and a construct was made in which part of ORF469 was deleted and replaced by erythromycin resistance cassette.Transformation of wild type strain of Synechocystis sp.PCC 6803 with this construct yielded a mutant in which ORF469 was deleted.In the resulting mutant, the light-independent pathway of chlorophyll biosynthesis was inactivated and availability of chlorophyll was fully dependent on light.When propagated the mutant in dark, the chlorophyll was non-detectable and protochlorophyllide with 645 nm fluorescence emission peak was accumulated.Meanwhile, the fluorescence emission peaks (excited at 435 nm) of thylakoids at 685 nm, 695 nm and 725 nm, which represented relative chlorophyll-binding proteins, disappeared.Upon return of dark-grown ORF469 mutant to the light, greening occurred and chlorophyll was synthesized to assembly fluorescence emission components in photosystems.Newly synthesized chlorophyll combined the fluorescence component of 685 nm at first, then 725 nm and 695 nm at last, which indicates a pecking order for biogenesis of chlorophyll-binding proteins when availability of chlorophyll is limited.The mutant lacking ORF469 in Synechocystis sp.PCC 6803 was suggested as an excellent cyanobacterial system for studies on the interactions between chlorophyll and chlorophyll-binding proteins in photosystems.

  12. Effects of lanthanum nitrate on growth and chlorophyll fluorescence characteristics of Alternanthera philoxeroides under perchlorate stress

    Institute of Scientific and Technical Information of China (English)

    谢寅峰; 蔡贤雷; 刘伟龙; 陶功胜; 陈倩; 张强

    2013-01-01

    To investigate the effects of exogenous lanthanum (La) on Alternanthera philoxeroides (Mart.) Griseb under perchlorate stress, changes in the growth and physiological parameters were investigated in solution culture experiments under controlled condi-tions. Different concentrations of La (NO3)3 were used in our study. It was shown that 0.1 and 0.5 mg/L La3+alleviated the inhibition effect of perchlorate on A. philoxeroides, including relative growth yield, dry weight of different organs, leaf area and root activity. And La3+prevented decline in the relative chlorophyll content and chlorophyll fluorescence parameters including Fv/Fm, Fv'/Fm',ΦPSI and ETR induced by perchlorate stress. Moreover, 0.5 mg/L La3+showed an optimal mitigative effect, while excess La3+(5.0 mg/L) led to synergistic effect on stress. Correlation analysis revealed a significant positive relationship between growth indexes and the chlorophyll fluorescence parameters, root activity and relative chlorophyll content (p<0.05). The results suggested that appropriate concentration of La3+could effectively alleviate growth inhibition and injury of A. philoxeroides caused by perchlorate stress, and the mitigative effect of La3+might be achieved by improving root activity, maintaining chlorophyll content and promoting photochemical efficiency of photosystem II of A. philoxeroides under perchlorate stress.

  13. [Monitoring of the Moskva River Water Using Microbiological Parameters and Chlorophyll a Fluorescence].

    Science.gov (United States)

    Mosharova, I V; Il'inskii, V V; Matorin, D N; Mosharov, S A; Akulova, A Yu; Protopopov, F F

    2015-01-01

    The results of investigations of three Moskva River sites with different degree of pollution using a complex of microbiological characteristics and the parameters of chlorophyll a fluorescence are presented. We determined that the bacterioplankton seasonal dynamics at less polluted waters (Tushino and Vorobyovy Gory) were similar and differed significantly from one in more polluted waters (Dzerzhinskii). The number of bacteria with active electron transport chain, as well as their share in the bacterioplankton structure, was higher in the water of Dzerzhinskii (average annual values of 0.23 x 10(6) cells/mL and 14%), that in the less polluted water of Tushino and Vorobyovy Gory (0.14 x 10(6) cells/mL; 6% and 0.15 x 10(6) cells/mL; 7%, respectively). From April to October, the content of chlorophyll a and its photosynthetic activity were the highest in Tushino. In Dzerzhinskii, during spring the increase in photosynthetic activity commenced earlier and was more intensive that the increase in chlorophyll a content, i.e., the increase in phytoplankton biomass was temporarily suppressed. We suggest association of this phenomenon with suppression of organic matter synthesis by phytoplankton due to the high water pollution in Dzerzhinskii. The second autumn peak of chlorophyll a content, that was typical of clear water and was observed in Tushino, did not occur in Dzerzhinskii. We recommend combined application of these microbiological parameters and characteristics of chlorophyll a fluorescence for a monitoring.

  14. In Vivo Single-Cell Fluorescence and Size Scaling of Phytoplankton Chlorophyll Content.

    Science.gov (United States)

    Álvarez, Eva; Nogueira, Enrique; López-Urrutia, Ángel

    2017-04-01

    In unicellular phytoplankton, the size scaling exponent of chlorophyll content per cell decreases with increasing light limitation. Empirical studies have explored this allometry by combining data from several species, using average values of pigment content and cell size for each species. The resulting allometry thus includes phylogenetic and size scaling effects. The possibility of measuring single-cell fluorescence with imaging-in-flow cytometry devices allows the study of the size scaling of chlorophyll content at both the inter- and intraspecific levels. In this work, the changing allometry of chlorophyll content was estimated for the first time for single phytoplankton populations by using data from a series of incubations with monocultures exposed to different light levels. Interspecifically, our experiments confirm previous modeling and experimental results of increasing size scaling exponents with increasing irradiance. A similar pattern was observed intraspecifically but with a larger variability in size scaling exponents. Our results show that size-based processes and geometrical approaches explain variations in chlorophyll content. We also show that the single-cell fluorescence measurements provided by imaging-in-flow devices can be applied to field samples to understand the changes in the size dependence of chlorophyll content in response to environmental variables affecting primary production.IMPORTANCE The chlorophyll concentrations in phytoplankton register physiological adjustments in cellular pigmentation arising mainly from changes in light conditions. The extent of these adjustments is constrained by the size of the phytoplankton cells, even within single populations. Hence, variations in community chlorophyll derived from photoacclimation are also dependent on the phytoplankton size distribution.

  15. Fluorescence quenching of fluoroquinolones by gold nanoparticles with different sizes and its analytical application

    Energy Technology Data Exchange (ETDEWEB)

    Amjadi, Mohammad, E-mail: amjadi@tabrizu.ac.ir; Farzampour, Leila

    2014-01-15

    The interaction of some fluoroquinolones including norfloxacin, ciprofloxacin, danofloxacin and ofloxacin with gold nanoparticles (AuNPs) of different sizes (8, 20 and 75 nm) was studied. In the studied systems, fluoroquinolones are noncovalently adsorbed onto the surface of AuNPs, which results in severe quenching of fluoroquinolones fluorescence possibly as a result of fluorescence resonance energy transfer. Stern–Volmer quenching constants were obtained and found to increase with an increase in the size of AuNPs. Moreover, the interactions between some thiols and fluoroquinolone-adsorbed AuNPs were investigated to explore the analytical applicability of the systems. It was found that upon the addition of thiols to fluoroquinolone-AuNPs systems the fluorescence of fluoroquinolones switches to “turn-on” due to the strong binding of thiols to AuNPs and removal of quinolines from NP surface. Under the optimum conditions, the fluorescence enhancement showed a linear relationship with the concentration of thiols, indicating the analytical usefulness of the system. -- Highlights: • Interaction of fluoroquinolones with AuNPs of different sizes was investigated. • The fluorescence of fluoroquinolones is efficiently quenched by AuNPs. • The fluorescence quenching efficiency increases by increasing NP size. • Fluoroquinolone-AuNPs systems can be used as sensitive turn-on sensors for thiols. • Danofloxacin-20-nm AuNPs system exhibits the highest sensitivity for thiols.

  16. Determination of torasemide by fluorescence quenching method with some dihalogenated fluorescein dyes as probes

    Science.gov (United States)

    Cui, Zhiping; Liu, Shaopu; Liu, Zhongfang; Li, Yuanfang; Hu, Xiaoli; Tian, Jing

    2013-10-01

    A novel fluorescence quenching method for the determination of torasemide (TOR) with some dihalogenated fluorescein dyes as fluorescence probes was developed. In acidulous medium, TOR could interact with some dihalogenated fluorescein dyes such as dichlorofluorescein (DCF), dibromofluorescein (DBF) and diiodofluorescein (DIF) to form binary complexes, which could lead to fluorescence quenching of above dihalogenated fluorescein dyes. The maximum fluorescence emission wavelengths were located at 532 nm (TOR-DCF), 535 nm (TOR-DBF) and 554 nm (TOR-DIF). The relative fluorescence intensities (ΔF = F0 - F) were proportional to the concentration of TOR in certain ranges. The detection limits were 4.8 ng mL-1 for TOR-DCF system, 9.8 ng mL-1 for TOR-DBF system and 35.1 ng mL-1 for TOR-DIF system. The optimum reaction conditions, influencing factors were studied; and the effect of coexisting substances was investigated owing to the highest sensitivity of TOR-DCF system. In addition, the reaction mechanism, composition and structure of the complex were discussed by quantum chemical calculation and Job's method. The fluorescence quenching of dihalogenated fluorescein dyes by TOR was a static quenching process judging from the effect of temperature and the Stern-Volmer plots. The method was satisfactorily applied to the determination of TOR in tablets and human urine samples.

  17. Chlorophyll fluorescence analysis: a guide to good practice and understanding some new applications.

    Science.gov (United States)

    Murchie, E H; Lawson, T

    2013-10-01

    Chlorophyll fluorescence is a non-invasive measurement of photosystem II (PSII) activity and is a commonly used technique in plant physiology. The sensitivity of PSII activity to abiotic and biotic factors has made this a key technique not only for understanding the photosynthetic mechanisms but also as a broader indicator of how plants respond to environmental change. This, along with low cost and ease of collecting data, has resulted in the appearance of a large array of instrument types for measurement and calculated parameters which can be bewildering for the new user. Moreover, its accessibility can lead to misuse and misinterpretation when the underlying photosynthetic processes are not fully appreciated. This review is timely because it sits at a point of renewed interest in chlorophyll fluorescence where fast measurements of photosynthetic performance are now required for crop improvement purposes. Here we help the researcher make choices in terms of protocols using the equipment and expertise available, especially for field measurements. We start with a basic overview of the principles of fluorescence analysis and provide advice on best practice for taking pulse amplitude-modulated measurements. We also discuss a number of emerging techniques for contemporary crop and ecology research, where we see continual development and application of analytical techniques to meet the new challenges that have arisen in recent years. We end the review by briefly discussing the emerging area of monitoring fluorescence, chlorophyll fluorescence imaging, field phenotyping, and remote sensing of crops for yield and biomass enhancement.

  18. Algal photosynthetic responses to toxic metals and herbicides assessed by chlorophyll a fluorescence.

    Science.gov (United States)

    Kumar, K Suresh; Dahms, Hans-Uwe; Lee, Jae-Seong; Kim, Hyung Chul; Lee, Won Chan; Shin, Kyung-Hoon

    2014-06-01

    Chlorophyll a fluorescence is established as a rapid, non-intrusive technique to monitor photosynthetic performance of plants and algae, as well as to analyze their protective responses. Apart from its utility in determining the physiological status of photosynthesizers in the natural environment, chlorophyll a fluorescence-based methods are applied in ecophysiological and toxicological studies to examine the effect of environmental changes and pollutants on plants and algae (microalgae and seaweeds). Pollutants or environmental changes cause alteration of the photosynthetic capacity which could be evaluated by fluorescence kinetics. Hence, evaluating key fluorescence parameters and assessing photosynthetic performances would provide an insight regarding the probable causes of changes in photosynthetic performances. This technique quintessentially provides non-invasive determination of changes in the photosynthetic apparatus prior to the appearance of visible damage. It is reliable, economically feasible, time-saving, highly sensitive, versatile, accurate, non-invasive and portable; thereby comprising an excellent alternative for detecting pollution. The present review demonstrates the applicability of chlorophyll a fluorescence in determining photochemical responses of algae exposed to environmental toxicants (such as toxic metals and herbicides). Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Towards a merged satellite and in situ fluorescence ocean chlorophyll product

    Directory of Open Access Journals (Sweden)

    H. Lavigne

    2011-12-01

    Full Text Available Understanding the ocean carbon cycle requires a precise assessment of phytoplankton biomass in the oceans. In terms of numbers of observations, satellite data represents the largest available data set. However, as they are limited to surface waters, they have to be merged with in situ observations. Amongst the in situ data, fluorescence profiles constitute the greatest data set available, because fluorometers operate routinely on oceanographic cruise since the seventies. Nevertheless, fluorescence is only a proxy of the Total Chlorophyll-a concentration and a data calibration is required. Calibration issues are, however, source of uncertainty and they have prevented a systematic and wide range exploitation of the fluorescence data set. In particular, very few attempts to standardize the fluorescence data bases exist. Consequently, merged estimations with other data sources (i.e. satellite are lacking.

    We propose a merging method to fill this gap. It consists firstly, in adjusting the fluorescence profile to impose a zero Chlorophyll-a concentration at depth. Secondly, each point of the fluorescence profile is then multiplied by a correction coefficient which forces the Chlorophyll-a integrated content measured on the fluorescence profile to be consistent with the concomitant ocean color observation. The method is close to the approach proposed by Boss et al. (2008 to calibrate fluorescence data of a profiling float, although important differences do exist. To develop and test our approach, in situ data from three open ocean stations (BATS, HOT and DYFAMED were used. Comparison of the so-called "satellite-corrected" fluorescence profiles with concomitant bottle derived estimations of Chlorophyll-a concentration was performed to evaluate the final error, which resulted to be of about 31 %. Comparison with the Boss et al. (2008 method, carried out on a subset of the DYFAMED data set simulating a profiling float

  20. Towards a merged satellite and in situ fluorescence ocean chlorophyll product

    Directory of Open Access Journals (Sweden)

    H. Lavigne

    2012-06-01

    Full Text Available Understanding the ocean carbon cycle requires a precise assessment of phytoplankton biomass in the oceans. In terms of numbers of observations, satellite data represent the largest available data set. However, as they are limited to surface waters, they have to be merged with in situ observations. Amongst the in situ data, fluorescence profiles constitute the greatest data set available, because fluorometers have operated routinely on oceanographic cruises since the 1970s. Nevertheless, fluorescence is only a proxy of the total chlorophyll a concentration and a data calibration is required. Calibration issues are, however, sources of uncertainty, and they have prevented a systematic and wide range exploitation of the fluorescence data set. In particular, very few attempts to standardize the fluorescence databases have been made. Consequently, merged estimations with other data sources (e.g. satellite are lacking.

    We propose a merging method to fill this gap. It consists firstly in adjusting the fluorescence profile to impose a zero chlorophyll a concentration at depth. Secondly, each point of the fluorescence profile is then multiplied by a correction coefficient, which forces the chlorophyll a integrated content measured on the fluorescence profile to be consistent with the concomitant ocean colour observation. The method is close to the approach proposed by Boss et al. (2008 to correct fluorescence data of a profiling float, although important differences do exist. To develop and test our approach, in situ data from three open ocean stations (BATS, HOT and DYFAMED were used. Comparison of the so-called "satellite-corrected" fluorescence profiles with concomitant bottle-derived estimations of chlorophyll a concentration was performed to evaluate the final error (estimated at 31%. Comparison with the Boss et al. (2008 method, using a subset of the DYFAMED data set, demonstrated that the methods have similar

  1. Mechanisms of Fluorescence Quenching of Pr3+-Doped PbWO4 Crystal

    Institute of Scientific and Technical Information of China (English)

    Xiong Feibing; Luo Zundu; Huang Yidong

    2005-01-01

    Fluorescence decay curves of the 3P0 and 1D2 manifolds in Pr3+ doped PbWO4 crystal were measured at room temperature and fluorescence lifetimes of both manifolds were estimated. Combining with the radiative lifetimes of the manifolds calculated on the basis of the modified J-O theory, the main mechanisms for the fluorescence quenching of the manifolds were analyzed. The multi-phonon relaxation and the cross-relaxation energy transfer are the major reasons for the fluorescence quenching of the 3P0 and 1D2 manifolds, respectively. The Inokuti-Hirayama model was used to analyze the fluorescence decay curve of the 1D2 manifold and the cross-relaxation of dipole-dipole interaction was confirmed. Consequently, the 3P0 manifold is more favorable as an upper laser level than the 1D2 manifold.

  2. Optical sensing of peroxide using ceria nanoparticles via fluorescence quenching technique

    Science.gov (United States)

    Shehata, Nader; Samir, Effat; Gaballah, Soha; Salah, Mohammed

    2016-07-01

    This study introduces the application of ceria nanoparticles (NPs) as an optical sensor for peroxide using fluorescence quenching technique. Our synthesized ceria NPs have the ability to adsorb peroxides via its oxygen vacancies. Ceria NPs solution with added variable concentrations of hydrogen peroxides is exposed through near-UV excitation and the detected visible fluorescent emission is found to be at ˜520 nm. The fluorescent intensity peak is found to be reduced with increasing the peroxide concentrations due to static fluorescence quenching technique. The relative intensity change of the visible fluorescent emission has been reduced to more than 50% at added peroxide concentrations up to 10 wt. %. In order to increase ceria peroxides sensing sensitivity, lanthanide elements such as samarium (Sm) are used as ceria NPs dopant. This research work could be applied further in optical sensors of radicals in biomedical engineering and environmental monitoring.

  3. Fluorescent chlorophyll catabolites in bananas light up blue halos of cell death

    Science.gov (United States)

    Moser, Simone; Müller, Thomas; Holzinger, Andreas; Lütz, Cornelius; Jockusch, Steffen; Turro, Nicholas J.; Kräutler, Bernhard

    2009-01-01

    Breakdown of chlorophyll is a major contributor to the diagnostic color changes in fall leaves, and in ripening apples and pears, where it commonly provides colorless, nonfluorescent tetrapyrroles. In contrast, in ripening bananas (Musa acuminata) chlorophylls fade to give unique fluorescent catabolites (FCCs), causing yellow bananas to glow blue, when observed under UV light. Here, we demonstrate the capacity of the blue fluorescent chlorophyll catabolites to signal symptoms of programmed cell death in a plant. We report on studies of bright blue luminescent rings on the peel of very ripe bananas, which arise as halos around necrotic areas in ‘senescence associated’ dark spots. These dark spots appear naturally on the peel of ripe bananas and occur in the vicinity of stomata. Wavelength, space, and time resolved fluorescence measurements allowed the luminescent areas to be monitored on whole bananas. Our studies revealed an accumulation of FCCs in luminescent rings, within senescing cells undergoing the transition to dead tissue, as was observable by morphological textural cellular changes. FCCs typically are short lived intermediates of chlorophyll breakdown. In some plants, FCCs are uniquely persistent, as is seen in bananas, and can thus be used as luminescent in vivo markers in tissue undergoing senescence. While FCCs still remain to be tested for their own hypothetical physiological role in plants, they may help fill the demand for specific endogenous molecular reporters in noninvasive assays of plant senescence. Thus, they allow for in vivo studies, which provide insights into critical stages preceding cell death. PMID:19805212

  4. Binding phenomena and fluorescence quenching. II: Photophysics of aromatic residues and dependence of fluorescence spectra on protein conformation

    Science.gov (United States)

    Callis, Patrik R.

    2014-12-01

    The three amino acids with aromatic ring side chains-phenylalanine (Phe), tyrosine (Tyr), and especially tryptophan (Trp) have played a long and productive role in helping unlock the secrets of protein behavior by optical spectroscopy (absorption, fluorescence, circular dichroism, etc.) In principle, an appropriately placed Trp will undergo fluorescence wavelength and/or intensity changes upon whatever functional process a protein performs. Although perceived to be enigmatic and not well understood, Trp is arguably now better understood than many of the extrinsic probes currently in use. Basic principles of intrinsic tryptophan fluorescence quenching and wavelength shifts in proteins are presented, with strong emphasis on the importance of electrostatics. The condensed description of findings from recent experiments and simulations of tryptophan fluorescence and intrinsic quenching in proteins is designed to help authors in planning and interpreting experimental results of ligand binding studies.

  5. Fluorescence quenching method for the determination of catechol with gold nanoparticles and tyrosinase hybrid system

    Institute of Scientific and Technical Information of China (English)

    Martin; M.F.Choi

    2010-01-01

    The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10~(-7)-1.0×10~(-3) mol L~(-1) and a detection limit 1.0×10~(-7) mol L~(-1) of catechol were obtained.o-Quinone intermediate produ...

  6. Fluorescence quenching of anthracene by N, N-diethylaniline in the O/W microemulsion

    Institute of Scientific and Technical Information of China (English)

    郭霞; 徐慧; 郭荣

    2000-01-01

    Photoinduced electron-transfer system of anthracene-N , N-di-ethylaniline (DEA) was studied in the oil in water (O/W) microemulsuins formed by SDS (sodium dodecyl sulfate), BA(benzyl alcohol) and H2O. The time-resolved fluorescence study showed that the fluorescence quenching of the excited anthracene by DEA occurs at the interface of the O/W micreomulsions Besides as the quencher of the excited anthrace ne, N, N-diethylaniine could act as a cosurfactant to change the structures of the microemulsions, just as BA did. The quenching rate constants for the different structures of the system were determined.

  7. The chlorophyll a fluorescence induction pattern in chloroplasts upon repetitive single turnover excitations: accumulation and function of QB-nonreducing centers.

    Science.gov (United States)

    Vredenberg, Wim; Kasalicky, Vojtech; Durchan, Milan; Prasil, Ondrej

    2006-03-01

    The increase of chlorophyll fluorescence yield in chloroplasts in a 12.5 Hz train of saturating single turnover flashes and the kinetics of fluorescence yield decay after the last flash have been analyzed. The approximate twofold increase in Fm relative to Fo, reached after 30-40 flashes, is associated with a proportional change in the slow (1-20 s) component of the multiphasic decay. This component reflects the accumulation of a sizeable fraction of QB-nonreducing centers. It is hypothesized that the generation of these centers occurs in association with proton transport across the thylakoid membrane. The data are quantitatively consistent with a model in which the fluorescence quenching of QB-nonreducing centers is reversibly released after second excitation and electron trapping on the acceptor side of Photosystem II.

  8. Bioluminophore and Flavin Mononucleotide Fluorescence Quenching of Bacterial Bioluminescence-A Theoretical Study.

    Science.gov (United States)

    Luo, Yanling; Liu, Ya-Jun

    2016-11-02

    Bacterial bioluminescence with continuous glow has been applied to the fields of environmental toxin monitoring, drug screening, and in vivo imaging. Nonetheless, the chemical form of the bacterial bioluminophore is still a bone of contention. Flavin mononucleotide (FMN), one of the light-emitting products, and 4a-hydroxy-5-hydro flavin mononucleotide (HFOH), an intermediate of the chemical reactions, have both been assumed candidates for the light emitter because they have similar molecular structures and fluorescence wavelengths. The latter is preferred in experiments and was assigned in our previous density functional study. HFOH displays weak fluorescence in solutions, but exhibits strong bioluminescence in the bacterial luciferase. FMN shows the opposite behavior; its fluorescence is quenched when it is bound to the luciferase. This is the first example of flavin fluorescence quenching observed in bioluminescent systems and is merely an observation, both the quenching mechanism and quencher are still unclear. Based on theoretical analysis of high-level quantum mechanics (QM), combined QM and molecular mechanics (QM/MM), and molecular dynamics (MD), this paper confirms that HFOH in its first singlet excited state is the bioluminophore of bacterial bioluminescence. More importantly, the computational results indicate that Tyr110 in the luciferase quenches the FMN fluorescence via an electron-transfer mechanism.

  9. Fluorescence Quenching Investigation for Janus Green B and used as Probe in Determination of Nucleic Acids

    Institute of Scientific and Technical Information of China (English)

    陈莉华; 刘六战; 沈含熙

    2005-01-01

    Fluorescence quenching of janus green B (JGB) in sodium dodecyl sulfate (SDS) micelle by nucleic acids (DNA) was studied using UV-vis absorption, steady state fluorescence emission methods and lifetime measurements. In the SDS micelle, weak fluorescence of JGB was enhanced, and the maximum emission shifted from 425 to 410 nm. In the presence of DNA, the fluorescence of JGB was quenched. Linear relationships between the fluorescence quenching (F0/F) and concentrations of DNA were observed in the range of 2.4×10-8 to 1.08×10-7mol·L-1 for calf thymus nucleic acids (ct DNA) and 1.9×10-8 to 3.8×10-8 mol·L-1 for fish sperm nucleic acids (fs DNA) when 2.5×10-5 mol·L-1 JGB was employed. The limit detection were 1.3×10-8 mol·L-1 for ct DNA and 6.4×10-9 mol·L-1 for fs DNA. At high DNA concentration, there was a systematic deviation from the Stem-Volmer equation due to the static and dynamic quenching occurring simultaneously. The proposed method was applied to the determination of the nucleic acids in chicken blood extraction and the analytical results were in good agreement with the UV-method.

  10. Fluorescence Quenching and Binding Interaction of l0-Methylacridinium Iodide to Nucleic Acids

    Institute of Scientific and Technical Information of China (English)

    孙险峰; 江致勤; 丁兵林

    2003-01-01

    Interaction of 10-methylacridinium iodide (MAI) as fluorescence probe with nucleobases, nucleosides and nucleic acids has been studied by UV-visible absorption and fluorescence spectroscopy. It was found that fluorescence of MAI is strongly quenched by the nucleobases, nucleosides and nucleic acids, respectively. The quenching follows the Stern-Volmer linear equation. The fluorescence quenching rate constant (kq) was measured to be 109-1010 (L/mol)/s within the range of diffusion-controlled rate limit, indicating that the interaction between MAI and nucleic acid and their precursors is characteristic of electron transfer mechanism. In addition, the binding interaction model of MAI to calf thymus DNA (ct-DNA) was further investigated. Apparent hypochromism in the absorption spectra of MAI was observed when MAI binds to ct-DNA.Three spectroscopic methods, which include (1) UV spectroscopy, (2) fluorescence quenching of MAI, (3) competitive dual-probe method of MAI and ethidium bromide (EB), were utilized to determine the affinity binding constants (K)of MAI and ct-DNA. The binding constants K obtained from the above methods gave consistent data in the same range (1.0-5.5) ×104 L/mol, which lend credibility to these measurements. The binding site number was determined to be 1.9. The influence of thermal denaturation and phosphate concentration on the binding was examined. The binding model of MAI to ct-DNA including intercalation and outside binding was investigated.

  11. Indication of transthylakoid proton-fluxes in Aegopodium podagraria L. by light-induced changes of plasmalemma potential, chlorophyll fluorescence and light-scattering.

    Science.gov (United States)

    Vanselow, K H; Dau, H; Hansen, U P

    1988-12-01

    The time course of the responses of chlorophyll fluorescence in leaves of Aegopodium podagraria to changes in irradiance does not necessarily show the time constant of thylakoid energization at energy fluence rates below 10-25 W·m(-2). In addition, other measures of thylakoid energization, such as lightscattering at 532 nm and the responses to saturating flashes, show that the related component disappears from these signals at low fluence rates, but not necessarily all together at the same fluence rate. However, this time constant still appears in the light-induced responses of the plasmalemma potential. This implies that the effect on the electrogenic proton pump in the plasmalemma is the most sensitive indicator of proton fluxes into the inner thylakoid space. These results are a further indication that energy-quenching is coupled ther indication that energy-quenching is coupled to transthylakoid proton fluxes via an intermediate, which is not active in Aegopodium podagraria at low irradiances.

  12. Effects of Low Temperature Stress and INA Bacteria on Chlorophyll a Fluorescence Induction Kinetics in Young Fruit of Two Apricot Cultivars

    Institute of Scientific and Technical Information of China (English)

    YANG Jian-min; MENG Qing-rui; PENG Wei-xiu; WANG Xue-dong; ZHANG Yuan-hui; SUN Fu-zai; ZHAO Ting-chang; LI Shao-hua

    2002-01-01

    Effects of low temperature and INA bacteria on the change of chlorophyll a fluorescence inyoung fruit from two apricot cultivars were investigated. Low temperature decreased the potential activity(Fv/Fo) ,conversion efficiency of primary light energy (Fv/Fm)of PS Ⅱ and photochemical quenching (qP) inyoung fruit of two apricot cultivars. Low temperature enhanced non-photochemical quenching qN, decreasingthe quantum yield of photosynthetic electron transfer. The presence of ice nucleating active (INA) bacteria in-tensified the effects of low temperature, raised the injury temperature threshold from - 4℃ to - 2 - - 3℃.INA bacteria can be a factor to induce frost susceptibility of apricot fruit. The amount of damaged PS Ⅱ activi-ty center was related to apricot fruit size and cultivar.

  13. Quenching and enhancement of single-molecule fluorescence under metallic and dielectric tips

    Science.gov (United States)

    Azoulay, J.; Débarre, A.; Richard, A.; Tchénio, P.

    2000-08-01

    We report on fluorescence experiments by apertureless near-field optical microscopy. We develop a simple model that demonstrates the importance of non-radiative transfer and that takes into account the dependence of non-radiative transfer on tip geometry. This process is in competition with field enhancement and it is a key process to understand the observed fluorescence enhancement factors. The analysis of the different factors involved in the global fluorescence enhancement or quenching leads to new strategies to reach resolution down to a few nanometers by apertureless fluorescence microscopy.

  14. Effects of nitrogen form on growth, CO₂ assimilation, chlorophyll fluorescence, and photosynthetic electron allocation in cucumber and rice plants.

    Science.gov (United States)

    Zhou, Yan-hong; Zhang, Yi-li; Wang, Xue-min; Cui, Jin-xia; Xia, Xiao-jian; Shi, Kai; Yu, Jing-quan

    2011-02-01

    Cucumber and rice plants with varying ammonium (NH(4)(+)) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO(3)(-))-grown plants, cucumber plants grown under NH(4)(+)-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO(2)) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O(2)-independent alternative electron flux, and increased O(2)-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH(4)(+)-grown plants had a higher O(2)-independent alternative electron flux than NO(3)(-)-grown plants. NO(3)(-) reduction activity was rarely detected in leaves of NH(4)(+)-grown cucumber plants, but was high in NH(4)(+)-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO(3)(-) assimilation, an effect more significant in NO(3)(-)-grown plants than in NH(4)(+)-grown plants. Meanwhile, NH(4)(+)-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO(3)(-) reduction, regardless of the N form supplied, while NH(4)(+)-sensitive plants had a high water-water cycle activity when NH(4)(+) was supplied as the sole N source.

  15. Investigation on the effect of fluorescence quenching of bovine serum albumin by cefoxitin sodium using fluorescence spectroscopy and synchronous fluorescence spectroscopy.

    Science.gov (United States)

    Li, Gaixia; Liu, Bao-Sheng; Zhang, Qiuju; Han, Rong

    2016-08-01

    The reaction mechanism of cefoxitin sodium with bovine serum albumin was investigated using fluorescence spectroscopy and synchronous fluorescence spectroscopy at different temperatures. The results showed that the change of binding constant of the synchronous fluorescence method with increasing temperature could be used to estimate the types of quenching mechanisms of drugs with protein and was consistent with one of fluorescence quenching method. In addition, the number of binding sites, type of interaction force, cooperativity between drug and protein and energy-transfer parameters of cefoxitin sodium and bovine serum albumin obtained from two methods using the same equation were consistent. Electrostatic force played a major role in the conjugation reaction between bovine serum albumin and cefoxitin sodium, and the type of quenching was static quenching. The primary binding site for cefoxitin sodium was sub-hydrophobic domain IIA, and the number of binding sites was 1. The value of Hill's coefficients (nH ) was approximately equal to 1, which suggested no cooperativity in the bovine serum albumin-cefoxitin sodium system. The donor-to-acceptor distance r fluorescence quenching of bovine serum albumin by cefoxitin sodium was also a non-radiation energy-transfer process. The results indicated that synchronous fluorescence spectrometry could be used to study the reaction mechanism between drug and protein, and was a useful supplement to the conventional method. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  16. Characterisation of dissolved organic matter fluorescence properties by PARAFAC analysis and thermal quenching.

    Science.gov (United States)

    Carstea, Elfrida M; Baker, Andy; Bieroza, Magdalena; Reynolds, Darren M; Bridgeman, John

    2014-09-15

    The fluorescence intensity of dissolved organic matter (DOM) in aqueous samples is known to be highly influenced by temperature. Although several studies have demonstrated the effect of thermal quenching on the fluorescence of DOM, no research has been undertaken to assess the effects of temperature by combining fluorescence excitation - emission matrices (EEM) and parallel factor analysis (PARAFAC) modelling. This study further extends previous research on thermal quenching by evaluating the impact of temperature on the fluorescence of DOM from a wide range of environmental samples, in the range 20 °C - 0 °C. Fluorescence intensity increased linearly with respect to temperature decrease at all temperatures down to 0 °C. Results showed that temperature affected the PARAFAC components associated with humic-like and tryptophan-like components of DOM differently, depending on the water type. The terrestrial humic-like components, C1 and C2 presented the highest thermal quenching in rural water samples and the lowest in urban water samples, while C3, the tryptophan-like component, and C4, a reprocessed humic-like component, showed opposite results. These results were attributed to the availability and abundance of the components or to the degree of exposure to the heat source. The variable thermal quenching of the humic-like components also indicated that although the PARAFAC model generated the same components across sites, the DOM composition of each component differed between them. This study has shown that thermal quenching can provide additional information on the characteristics and composition of DOM and highlighted the importance of correcting fluorescence data collected in situ.

  17. The amplified fluorescence quenching of heteroatomic conjugated polymers based on the "molecular wire" effects

    Institute of Scientific and Technical Information of China (English)

    HUANG Hongmei; WANG Kemin; XIAO Yi; ZHAI Qiuge; AN Delie; HUANG Shasheng; LI Du

    2003-01-01

    Tremendous interest has been evoked in the utility of the fluorescent conjugated polymers towards the creation of ultra-sensitive systems based on the molecular wire effects which can amplify the transduction events. Here, a series of new polymers —pyridine substitute poly (phen- ylene ethynylene)s are synthesized by Sonogashira-Hagihara coupling reaction. The impact of structure modification on the physical properties and spectral characteristics of polymers has been investigated. The quenching studies are carried out and exhibit that recognition site (pyridyle group) highly influences the quenching efficiency. The results show that polymer PI with pyridyl group entrapped in the conjugated backbone has the specific and sensitive response to Pd(Ⅱ). The fluorescence quenching of PⅠby Pd(Ⅱ) is about 65 times greater than that of model monomer.

  18. Photoprotective function of chloroplast avoidance movement: in vivo chlorophyll fluorescence study.

    Science.gov (United States)

    Sztatelman, Olga; Waloszek, Andrzej; Banaś, Agnieszka Katarzyna; Gabryś, Halina

    2010-06-15

    Light-induced chloroplast avoidance movement has long been considered to be a photoprotective mechanism. Here, we present an experimental model in which this function can be shown for wild type Arabidopsis thaliana. We used blue light of different fluence rates for chloroplast positioning, and strong red light inactive in chloroplast positioning as a stressing light. The performance of photosystem II was measured by means of chlorophyll fluorescence. After stressing light treatment, a smaller decrease in photosystem II quantum yield was observed for leaves with chloroplasts in profile position as compared with leaves with chloroplasts in face position. Three Arabidopsis mutants, phot2 (no avoidance response), npq1 (impaired zeaxanhtin accumulation) and stn7 (no state transition), were examined for their chloroplast positioning and chlorophyll fluorescence parameters under identical experimental conditions. The results obtained for these mutants revealed additional stressing effects of blue light as compared with red light.

  19. "Open-Box" Approach to Measuring Fluorescence Quenching Using an iPad Screen and Digital SLR Camera

    Science.gov (United States)

    Koenig, Michael H.; Yi, Eun P.; Sandridge, Matthew J.; Mathew, Alexander S.; Demas, James N.

    2015-01-01

    Fluorescence quenching is an analytical technique and a common undergraduate laboratory exercise. Unfortunately, a typical quenching experiment requires the use of an expensive fluorometer that measures the relative fluorescence intensity of a single sample in a closed compartment unseen by the experimenter. To overcome these shortcomings, we…

  20. A sensitive fluorescence quenching method for determination of bismuth with tiron

    Energy Technology Data Exchange (ETDEWEB)

    Taher, Mohammad Ali; Rahimi, Mina [Department of Chemistry, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Fazelirad, Hamid, E-mail: hamidfazelirad@gmail.com [Department of Chemistry, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Department of Chemistry, Science and Research Branch, Islamic Azad University, Yazd (Iran, Islamic Republic of); Young Researchers Society, Shahid Bahonar University of Kerman, P.O. Box 76175-133, Kerman (Iran, Islamic Republic of)

    2014-01-15

    We describe a fluorescence quenching method for determination of bismuth with tiron. The method is based on the reaction of tiron by bismuth(III) in acidic media. The influence of variables such as the pH, type of buffer, tiron concentration, reaction time and temperature were investigated. Under optimized conditions, the fluorescence quenching extent is proportional to the concentration of bismuth for Bi–tiron system at the range 0.13–2.09 μg mL{sup −1} and the detection limit is 0.05 μg mL{sup −1}. The proposed sensor presented good repeatability, evaluated in terms of relative standard deviation (R.S.D.=±0.498%) for 11 replicates. This sensitive, rapid and accurate method has been successfully applied to the determination of trace bismuth(III) in water and hair samples and certified reference materials. -- Highlights: • No previous paper report on use of fluorescence quenching for determination of Bi. • Fluorescence quenching of trion is a sensitive method for determination of Bi(III). • Under the optimum conditions the detection limit is very low (0.05 μg mL{sup −1}). • The procedure is simple and safe and has high tolerance limit to interferences.

  1. Studies on interactions between plant secondary metabolites and glutathione transferase using fluorescence quenching method.

    Science.gov (United States)

    Zhang, Xian; Cheng, Xinsheng; Wang, Chuanqin; Xue, Zechun; Yang, Liwen; Xi, Zheng

    2007-04-01

    The interactions between plant secondary metabolites (tannic acid, rutin, cinnamic acid and catechin) and glutathione transferase (GST) were investigated by fluorescence and UV-Vis absorption spectroscopy. Intrinsic fluorescence of GST was measured by selectively exciting their tryptophan (Trp) residues and quenching constants were determined using the Stern-Volmer equation. The binding affinity was found to be strongest for tannic acid and ranked in the order tannic acid>rutin>cinnamic acid>catechin. The pH values in the range of 6.7-7.9, except for tannic acid, did not affect significantly the affinity of rutin, cinnamic acid and catechin with GST. Results showed that the fluorescence quenching of GST was a static_quenching. Fluorescence quenching and UV-Vis absorption spectroscopy suggested that only the tannic acid changed the microenvironment of the Trp residues. Furthermore, the number of binding sites and binding constants at different pH values showed that tannic acid had strongest affinity towards GST and hydrogen bonding played an important role in the affinity between GST and the metabolites.

  2. Chlorophyll a Covalently Bonded to Organo-Modified Translucent Silica Xerogels: Optimizing Fluorescence and Maximum Loading

    Directory of Open Access Journals (Sweden)

    M. A. García-Sánchez

    2016-07-01

    Full Text Available Chlorophyll is a pyrrolic pigment with important optical properties, which is the reason it has been studied for many years. Recently, interest has been rising with respect to this molecule because of its outstanding physicochemical properties, particularly applicable to the design and development of luminescent materials, hybrid sensor systems, and photodynamic therapy devices for the treatment of cancer cells and bacteria. More recently, our research group has been finding evidence for the possibility of preserving these important properties of substrates containing chlorophyll covalently incorporated within solid pore matrices, such as SiO2, TiO2 or ZrO2 synthesized through the sol-gel process. In this work, we study the optical properties of silica xerogels organo-modified on their surface with allyl and phenyl groups and containing different concentrations of chlorophyll bonded to the pore walls, in order to optimize the fluorescence that these macrocyclic species displays in solution. The intention of this investigation was to determine the maximum chlorophyll a concentration at which this molecule can be trapped inside the pores of a given xerogel and to ascertain if this pigment remains trapped as a monomer, a dimer, or aggregate. Allyl and phenyl groups were deposited on the surface of xerogels in view of their important effects on the stability of the molecule, as well as over the fluorescence emission of chlorophyll; however, these organic groups allow the trapping of either chlorophyll a monomers or dimers. The determination of the above parameters allows finding the most adequate systems for subsequent in vitro or in vivo studies. The characterization of the obtained xerogels was performed through spectroscopic absorption, emission and excitation spectra. These hybrid systems can be employed as mimics of natural systems; the entrapment of chlorophyll inside pore matrices indicates that it is possible to exploit some of the most

  3. Simplified, rapid, and inexpensive estimation of water primary productivity based on chlorophyll fluorescence parameter Fo.

    Science.gov (United States)

    Chen, Hui; Zhou, Wei; Chen, Weixian; Xie, Wei; Jiang, Liping; Liang, Qinlang; Huang, Mingjun; Wu, Zongwen; Wang, Qiang

    2017-04-01

    Primary productivity in water environment relies on the photosynthetic production of microalgae. Chlorophyll fluorescence is widely used to detect the growth status and photosynthetic efficiency of microalgae. In this study, a method was established to determine the Chl a content, cell density of microalgae, and water primary productivity by measuring chlorophyll fluorescence parameter Fo. A significant linear relationship between chlorophyll fluorescence parameter Fo and Chl a content of microalgae, as well as between Fo and cell density, was observed under pure-culture conditions. Furthermore, water samples collected from natural aquaculture ponds were used to validate the correlation between Fo and water primary productivity, which is closely related to Chl a content in water. Thus, for a given pure culture of microalgae or phytoplankton (mainly microalgae) in aquaculture ponds or other natural ponds for which the relationship between the Fo value and Chl a content or cell density could be established, Chl a content or cell density could be determined by measuring the Fo value, thereby making it possible to calculate the water primary productivity. It is believed that this method can provide a convenient way of efficiently estimating the primary productivity in natural aquaculture ponds and bringing economic value in limnetic ecology assessment, as well as in algal bloom monitoring.

  4. Relationship between photosynthetic pigments and chlorophyll fluorescence in soybean under varying phosphorus nutrition at ambient and elevated CO2

    Science.gov (United States)

    Photosynthetic pigments such as chlorophyll (Chl) a, Chl b and carotenoids concentration, and chlorophyll fluorescence (CF) have widely been used as indicators of stress and photosynthetic performance in plants. Although photosynthetic pigments and CF are partly interdependent due to absorption and ...

  5. Effect of changes in chlorophyll concentration on photosynthetic properties I. Fluorescence and absorption of greening bean leaves

    NARCIS (Netherlands)

    Goedheer, J.C.

    1961-01-01

    In order to obtain new information about the way of functioning of chlorophyll in vivo a study was made of optical properties and photosynthesis under condition of a low chlorophyll content in the leave. It was found that the fluorescence yeild of greening bean leaves decreased from a value

  6. Effect of changes in chlorophyll concentration on photosynthetic properties I. Fluorescence and absorption of greening bean leaves

    NARCIS (Netherlands)

    Goedheer, J.C.

    1961-01-01

    In order to obtain new information about the way of functioning of chlorophyll in vivo a study was made of optical properties and photosynthesis under condition of a low chlorophyll content in the leave. It was found that the fluorescence yeild of greening bean leaves decreased from a value approxim

  7. Study on the Interaction between Cephalosporin Drugs and Papain by Spectroscopic Method: Equivalence of Fluorescence Quenching and Enhancement Equation%Study on the Interaction between Cephalosporin Drugs and Papain by Spectroscopic Method: Equivalence of Fluorescence Quenching and Enhancement Equation

    Institute of Scientific and Technical Information of China (English)

    杨曼曼; 席小莉; 杨频

    2011-01-01

    The interaction between two 4th generation of new cephalosporin drugs and papain was studied through spectroscopy method at different temperatures. Their dissociation constants were calculated by using theoretical formula of fluorescence quenching and fluorescence enhancement, respectively, and their corresponding thermodynamic functions, dipole-dipole non-radiative energy-transfer-efficiency and the action distances of acceptor-substrate etc. were calculated further. Analysis reveals that, the quenching on papain by cefpirome and cefepime is basically due to the dipole-dipole non-radiation energy-transfer and certain dynamic collision between donor and acceptor, the interaction between drug and papain is mainly hydrophobic which may provide useful information for pharmacological and metabolic study on papain. In this paper fluorescence quenching is regarded as negative fluorescence enhancement, and two kinds of theoretical formula of fluorescence quenching and fluorescence enhancement were used to calculate the experimental data of fluorescence quenching of a same batch, and very close results were obtained but with certain difference. The results not only display the equivalence of the two theoretical equations when treating acceptor-substrate action, but also show that the thermodynamic data based on the theoretical formula of fluorescence enhancement (4), which is deduced by us, are more reasonable. So we suggest that even in the process of studying the fluorescence quenching between receptor-substrate, using the theoretical formula of fluorescence enhancement (4) can get more reliable results.

  8. Effect of arsenic on reflectance spectra and chlorophyll fluorescence of aquatic plants.

    Science.gov (United States)

    Iriel, Analia; Dundas, Gavin; Fernández Cirelli, Alicia; Lagorio, Maria G

    2015-01-01

    Arsenic pollution of groundwater is a serious problem in many regions of Latin America that causes severe risks to human health. As a consequence, non-destructive monitoring methodologies, sensitive to arsenic presence in the environment and able to perform a rapid screening of large polluted areas, are highly sought-after. Both chlorophyll - a fluorescence and reflectance of aquatic plants may be potential indicators to sense toxicity in water media. In this work, the effects of arsenic on the optical and photophysical properties of leaves of different aquatic plants (Vallisneria gigantea, Azolla filiculoides and Lemna minor) were evaluated. Reflectance spectra were recorded for the plant leaves from 300 to 2400 nm. The spectral distribution of the fluorescence was also studied and corrected for light re-absorption processes. Photosynthetic parameters (Fv/Fm and ΦPSII) were additionally calculated from the variable chlorophyll fluorescence recorded with a pulse amplitude modulated fluorometer. Fluorescence and reflectance properties for V. gigantea and A. filiculoides were sensitive to arsenic presence in contrast to the behaviour of L. minor. Observed changes in fluorescence spectra could be interpreted in terms of preferential damage in photosystem II. The quantum efficiency of photosystem II for the first two species was also affected, decreasing upon arsenic treatment. As a result of this research, V. gigantea and A. filiculoides were proposed as bioindicators of arsenic occurrence in aquatic media.

  9. Forest productivity and water stress in Amazonia: observations from GOSAT chlorophyll fluorescence.

    Science.gov (United States)

    Lee, Jung-Eun; Frankenberg, Christian; van der Tol, Christiaan; Berry, Joseph A; Guanter, Luis; Boyce, C Kevin; Fisher, Joshua B; Morrow, Eric; Worden, John R; Asefi, Salvi; Badgley, Grayson; Saatchi, Sassan

    2013-06-22

    It is unclear to what extent seasonal water stress impacts on plant productivity over Amazonia. Using new Greenhouse gases Observing SATellite (GOSAT) satellite measurements of sun-induced chlorophyll fluorescence, we show that midday fluorescence varies with water availability, both of which decrease in the dry season over Amazonian regions with substantial dry season length, suggesting a parallel decrease in gross primary production (GPP). Using additional SeaWinds Scatterometer onboard QuikSCAT satellite measurements of canopy water content, we found a concomitant decrease in daily storage of canopy water content within branches and leaves during the dry season, supporting our conclusion. A large part (r(2) = 0.75) of the variance in observed monthly midday fluorescence from GOSAT is explained by water stress over moderately stressed evergreen forests over Amazonia, which is reproduced by model simulations that include a full physiological representation of photosynthesis and fluorescence. The strong relationship between GOSAT and model fluorescence (r(2) = 0.79) was obtained using a fixed leaf area index, indicating that GPP changes are more related to environmental conditions than chlorophyll contents. When the dry season extended to drought in 2010 over Amazonia, midday basin-wide GPP was reduced by 15 per cent compared with 2009.

  10. Low dose detection of γ radiation via solvent assisted fluorescence quenching.

    Science.gov (United States)

    Han, Ji-Min; Xu, Miao; Wang, Brian; Wu, Na; Yang, Xiaomei; Yang, Haori; Salter, Bill J; Zang, Ling

    2014-04-02

    Development of low cost, easy-to-use chemical sensor systems for low dose detection of γ radiation remains highly desired for medical radiation therapy and nuclear security monitoring. We report herein on a new fluorescence sensor molecule, 4,4'-di(1H-phenanthro[9,10-d]imidazol-2-yl)biphenyl (DPI-BP), which can be dissolved into halogenated solvents (e.g., CHCl3, CH2Cl2) to enable instant detection of γ radiation down to the 0.01 Gy level. The sensing mechanism is primarily based on radiation induced fluorescence quenching of DPI-BP. Pristine DPI-BP is strongly fluorescent in halogenated solvents. When exposed to γ radiation, the halogenated solvents decompose into various radicals, including hydrogen and chlorine, which then combine to produce hydrochloric acid (HCl). This strong acid interacts with the imidazole group of DPI-BP to convert it into a DPI-BP/HCl adduct. The DPI-BP/HCl adduct possesses a more planar configuration than DPI-BP, enhancing the π-π stacking and thus molecular aggregation. The strong molecular fluorescence of DPI-BP gets quenched upon aggregation, due to the π-π stacking interaction (forming forbidden low-energy excitonic transition). Interestingly the quenched fluorescence can be recovered simply by adding base (e.g., NaOH) into the solution to dissociate the DPI-BP/HCl adduct. Such sensing mechanism was supported by systematic investigations based on HCl titration and dynamic light scattering measurements. To further confirm that the aggregation caused fluorescence quenching, a half size analogue of DPI-BP, 2-phenyl-1H-phenanthro[9,10-d]imidazole (PI-Ph), was synthesized and investigated in comparison with the observations of DPI-BP. PI-Ph shares the same imidazole conjugation structure with DPI-BP and is expected to bind the same way with HCl. However, PI-Ph did not show fluorescence quenching upon binding with HCl likely due to the smaller π-conjugation structure, which can hardly enforce the π-π stacking assembly. Combining

  11. High temperature stress monitoring and detection using chlorophyll a fluorescence and infrared thermography in chrysanthemum (Dendranthema grandiflora)

    DEFF Research Database (Denmark)

    Wakjera, Eshetu Janka; Körner, Oliver; Rosenqvist, Eva

    2013-01-01

    (PSII) and stomatal conductance (gs). A combination of chlorophyll a fluorescence, gas exchange measurements and infrared thermography was applied using Chrysanthemum (Dendranthema grandiflora Tzvelev) cultivar ‘Coral Charm’ as a model species. Increasing temperature had a highly significant effect...

  12. Rapid assessment of different oxygenic phototrophs and single-cell photosynthesis with multicolour variable chlorophyll fluorescence imaging

    DEFF Research Database (Denmark)

    Trampe, Erik Christian Løvbjerg; Kolbowski, J.; Schreiber, U.

    2011-01-01

    We present a new system for microscopic multicolour variable chlorophyll fluorescence imaging of aquatic phototrophs. The system is compact and portable and enables microscopic imaging of photosynthetic performance of individual cells and chloroplasts using different combinations of blue, green, ...

  13. Development of the spectrometric imaging apparatus of laser induced fluorescence from plants and estimation of chlorophyll contents of rice leaves; Laser reiki keiko sokutei sochi no kaihatsu to inehanai no chlorophyll ganryo no suitei

    Energy Technology Data Exchange (ETDEWEB)

    Nakaya, K.; Shoji, K.; Hanyu, H.

    1999-05-01

    Photosynthetic activity of plants is an important factor to assess the micrometeorological effect of plant canopy or to estimate the influence of circumstances such as water stress. Light illumination induces fluorescence from a leaf or suspension of chloroplasts. The red chlorophyll fluorescence had been used to determine the process of the electron transportation in photosynthetic reaction. The fluorescence source other than chlorophyll is not announced sufficiently, but is supposed to be useful to determine the contents of the substance corresponding to physiological response of plants. We developed a fluorescence imaging apparatus to observe spectrum and distribution of laser induced fluorescence from a leaf. Pulsed UV-laser (Nd:YAG) induced blue-green fluorescence and red chlorophyll fluorescence from a green leaf. The pulse modulated measuring light and CCD with image-intensifier (ICCD) enable to detect the fluorescence from plants under illumination. The laser induced fluorescence (LIF) spectra were investigated to estimate the chlorophyll contents in leaves of rice. During the greening course of dark grown etiolated rice leaves, chlorophyll contents were determined using the extraction of leaves and steady state LIF spectra were measured. As a result, the ratio of fluorescent intensity between blue-green and red peaks (F460/F740 and F510/F740) decreased in proportion to alteration of chlorophyll contents respectively. These fluorescence intensity ratios perform more precise estimation of higher chlorophyll contents of leaves than reported red chlorophyll fluorescence intensity ratio (F690/E740). (author)

  14. [Characterizing the interaction between roxarsone and humic acid by fluorescence quenching experiment].

    Science.gov (United States)

    Zhu, Jiang-Peng; Mei, Ting; Peng, Yun; Ge, Si-Yi; Li, Shi-Yin; Wang, Guo-Xiang

    2014-07-01

    In this study, the methods of fluorescence spectroscopy and fluorescence quenching titration technique were used to identify the interactions between humic acid (HA) and roxarsone (ROX). Effects of HA concentration, pH and temperature on the bonding strength between HA and ROX were investigated. The results showed that the four fluorescence peaks (E(x)/E(m) = 300 nm/480 nm, 370 nm/480 nm, 420 nm/500 nm, 460 nm/520 nm, marked as peak A, B, C, D respectively) of HA could be quenched by ROX. The extent of decreases in fluorescence intensities of different peaks was different and followed the order of C > B > A > D. The common logarithm of association constants (lg K) between peak A and ROX increased slightly with the increase of HA concentration and were much larger than the bimolecular quenching constant of O2. It was confirmed that the carboxyl groups and the carboxide groups of HA were quenched statically by ROX. The lg K values fluctuated between 3.55 L x mol(-1) and 3.98 L x mol(-1) when pH ranged from 5.00 to 9.00, and the maximum value occurred at pH 6.00. It might be resulted from the fact that pH could change the formation of ROX and conformation of phenolic hydroxyl groups and carboxyl groups in HA. The lg K values decreased and fluctuated between 2.65 L x mol(-1) and 3.89 L x mol(-1) with temperature ranging from 25.0 degrees C to 55.0 degrees C, which further confirmed the static quenching interaction between HA and ROX. Transient-fluorescence spectrum analyses and liner model simulations revealed that single static quenching was the main mechanism between ROX and the functional groups of fluorescence peak A, B, D in HA, and combined dynamic and static quenching was the main mechanism between ROX and the functional groups of peak C in HA.

  15. Green tea catechins quench the fluorescence of bacteria-conjugated Alexa fluor dyes.

    Science.gov (United States)

    Zhao, Lin; Li, Wei; Zhu, Shu; Tsai, Sheena; Li, Jianhua; Tracey, Kevin J; Wang, Ping; Fan, Saijun; Sama, Andrew E; Wang, Haichao

    2013-10-01

    Accumulating evidence suggests that Green tea polyphenolic catechins, especially the (-)-epigallocatechin gallate (EGCG), can be cross-linked to many proteins, and confer a wide range of anti-bacterial activities possibly by damaging microbial cytoplasmic lipids and proteins. At the doses that conferred protection against lethal polymicrobial infection (induced by cecal ligation and puncture), EGCG significantly reduced bacterial loads particularly in the liver and lung. To elucidate its bactericidal mechanisms, we determined whether EGCG affected the fluorescence intensities of bacteria-conjugated Alexa Fluor 488 or 594 dyes. When mixed with unconjugated Alexa Fluor 488 or 594 dyes, EGCG or analogs did not affect the fluorescence intensity of these dyes. In a sharp contrast, EGCG and some analogs (e.g., Catechin Gallate, CG), markedly reduced the fluorescence intensity of Gram-positive Staphylococcus aureus-conjugated Alexa 594 and Gram-negative Escherichia coli-conjugated Alexa 488. Interestingly, co-treatment with ethanol impaired the EGCG-mediated fluorescence quenching of the G(+) S. aureus, but not of the G(-) E. coli-conjugated Alexa Flour dyes. In light of the notion that Alexa Fluor dyes can be quenched by aromatic amino acids, it is plausible that EGCG exerts antimicrobial activities possibly by altering microbial protein conformations and functions. This possibility can now be explored by screening other fluorescence-quenching agents for possible antimicrobial activities.

  16. Ensemble and single-molecule studies on fluorescence quenching in transition metal bipyridine-complexes.

    Directory of Open Access Journals (Sweden)

    Dominik Brox

    Full Text Available Beyond their use in analytical chemistry fluorescent probes continuously gain importance because of recent applications of single-molecule fluorescence spectroscopy to monitor elementary reaction steps. In this context, we characterized quenching of a fluorescent probe by different metal ions with fluorescence spectroscopy in the bulk and at the single-molecule level. We apply a quantitative model to explain deviations from existing standard models for fluorescence quenching. The model is based on a reversible transition from a bright to a dim state upon binding of the metal ion. We use the model to estimate the stability constants of complexes with different metal ions and the change of the relative quantum yield of different reporter dye labels. We found ensemble data to agree widely with results from single-molecule experiments. Our data indicates a mechanism involving close molecular contact of dye and quenching moiety which we also found in molecular dynamics simulations. We close the manuscript with a discussion of possible mechanisms based on Förster distances and electrochemical potentials which renders photo-induced electron transfer to be more likely than Förster resonance energy transfer.

  17. Exciton-polaron quenching in organic thin-film transistors studied by fluorescence lifetime imaging microscopy

    DEFF Research Database (Denmark)

    Jensen, Per Baunegaard With; Leißner, Till; Osadnik, Andreas

    Organic semiconductors show great potential in electronic and optical applications. However, a major challenge is the degradation of the semiconductor materials that cause a reduction in device performance. Here, we present our investigations of Organic Thin Film Transistors (OTFT) based...... that correlates with the local charge density indicates a pronounced exciton quenching by the injected charges. Subsequent FLIM measurements on previously biased OTFT devices show a general decrease in fluorescence lifetime suggesting degradation of the organic semiconductor. This is correlated with the results...... on the material 5,5-bis(naphthyl)-2,20-bithiophene (NaT2). These types of OTFT have previously been shown to have light emitting properties. Fluorescence Lifetime Imaging Microscopy (FLIM) has been used to investigate the exciton-polaron quenching in biased OTFTs. A clear reduction in fluorescence lifetime...

  18. Determination of L-phenylalanine by cucurbit[7]uril sensitized fluorescence quenching method

    Institute of Scientific and Technical Information of China (English)

    Chang Feng Li; Li Ming Du; Hao Wu; Ying Xia Chang

    2011-01-01

    The determination method of L-phenylalanine (LPA) by fluorescence quenching was developed. The assay was based on the combination of the cucurbit[7]uril (CB[7]) with palmatine hydrochloride (PAL) reaction. In the presence of CB[7], the fluorescence of PAL was quenched by LPA which can be employed to detect LPA. Under the optimal conditions, a linear range 3.63 × 10-8-9.68 × 10-6 mol/L and a detection limit 1.27 × 10-8 mol/L of LPA were obtained. The relative standard deviation (R.S.D) was 1.8% obtained from a series of11 standards each containing 6.05 × 10-6 mol/L oLPA. This paper also discusses the mechanism of fluorescence indicator probe.

  19. Ultrasensitive fluorescence immunoassay for detection of ochratoxin A using catalase-mediated fluorescence quenching of CdTe QDs

    Science.gov (United States)

    Huang, Xiaolin; Zhan, Shengnan; Xu, Hengyi; Meng, Xianwei; Xiong, Yonghua; Chen, Xiaoyuan

    2016-04-01

    Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to perform a dynamic linear detection of OTA ranging from 0.05 pg mL-1 to 10 pg mL-1. The half maximal inhibitory concentration was 0.53 pg mL-1 and the limit of detection was 0.05 pg mL-1. These values were approximately 283- and 300-folds lower than those of horseradish peroxidase (HRP)-based conventional ELISA, respectively. The reported method is accurate, highly reproducible, and specific against other mycotoxins in agricultural products as well. In summary, the developed fluorescence immunoassay based on H2O2-induced fluorescence quenching of CdTe QDs can be used for the rapid and highly sensitive detection of mycotoxins or haptens in food safety monitoring.Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H2O2)-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H2O2-induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H2O2, our proposed method could be used to

  20. The interrelationship between the lower oxygen limit, chlorophyll fluorescence and the xanthophyll cycle in plants.

    Science.gov (United States)

    Wright, A Harrison; DeLong, John M; Gunawardena, Arunika H L A N; Prange, Robert K

    2011-03-01

    The lower oxygen limit (LOL) in plants may be identified through the measure of respiratory gases [i.e. the anaerobic compensation point (ACP) or the respiratory quotient breakpoint (RQB)], but recent work shows it may also be identified by a sudden rise in dark minimum fluorescence (F(o)). The interrelationship between aerobic respiration and fermentative metabolism, which occur in the mitochondria and cytosol, respectively, and fluorescence, which emanates from the chloroplasts, is not well documented in the literature. Using spinach (Spinacia oleracea), this study showed that F(o) and photochemical quenching (q(P)) remained relatively unchanged until O(2) levels dropped below the LOL. An over-reduction of the plastoquinone (PQ) pool is believed to increase F(o) under dark + anoxic conditions. It is proposed that excess cytosolic reductant due to inhibition of the mitochondria's cytochrome oxidase under low-O(2), may be the primary reductant source. The maximum fluorescence (F(m)) is largely unaffected by low-O(2) in the dark, but was severely quenched, mirroring changes to the xanthophyll de-epoxidation state (DEPS), under even low-intensity light (≈4 μmol m(-2) s(-1)). In low light, the low-O(2)-induced increase in F(o) was also quenched, likely by non-photochemical and photochemical means. The degree of quenching in the light was negatively correlated with the level of ethanol fermentation in the dark. A discussion detailing the possible roles of cyclic electron flow, the xanthophyll cycle, chlororespiration and a pathway we termed 'chlorofermentation' were used to interpret fluorescence phenomena of both spinach and apple (Malus domestica) over a range of atmospheric conditions under both dark and low-light.

  1. Photochemical studies of a fluorescent chlorophyll catabolite--source of bright blue fluorescence in plant tissue and efficient sensitizer of singlet oxygen.

    Science.gov (United States)

    Jockusch, Steffen; Turro, Nicholas J; Banala, Srinivas; Kräutler, Bernhard

    2014-02-01

    Fluorescent chlorophyll catabolites (FCCs) are fleeting intermediates of chlorophyll breakdown, which is seen as an enzyme controlled detoxification process of the chlorophylls in plants. However, some plants accumulate large amounts of persistent FCCs, such as in senescent leaves and in peels of yellow bananas. The photophysical properties of such a persistent FCC (Me-sFCC) were investigated in detail. FCCs absorb in the near UV spectral region and show blue fluorescence (max at 437 nm). The Me-sFCC fluorescence had a quantum yield of 0.21 (lifetime 1.6 ns). Photoexcited Me-sFCC intersystem crosses into the triplet state (quantum yield 0.6) and generates efficiently singlet oxygen (quantum yield 0.59). The efficient generation of singlet oxygen makes fluorescent chlorophyll catabolites phototoxic, but might also be useful as a (stress) signal and for defense of the plant tissue against infection by pathogens.

  2. High-contrast visualization of graphene oxide on dye-sensitized glass, quartz, and silicon by fluorescence quenching.

    Science.gov (United States)

    Treossi, Emanuele; Melucci, Manuela; Liscio, Andrea; Gazzano, Massimo; Samorì, Paolo; Palermo, Vincenzo

    2009-11-04

    We present a novel approach for detecting and visualizing graphene oxide (GO) with high contrast on different substrates, including glass, quartz, and silicon. Visualization of GO sheets is accomplished through quenching the fluorescence of a thiophene dye, giving high optical contrast without the need to use interference methods. A comparison of fluorescence, AFM, and XRD measurements confirmed that even a single GO sheet can completely quench the fluorescence and thus be quickly visualized.

  3. A Graphical User Interface for Parameterizing Biochemical Models of Photosynthesis and Chlorophyll Fluorescence

    Science.gov (United States)

    Kornfeld, A.; Van der Tol, C.; Berry, J. A.

    2015-12-01

    Recent advances in optical remote sensing of photosynthesis offer great promise for estimating gross primary productivity (GPP) at leaf, canopy and even global scale. These methods -including solar-induced chlorophyll fluorescence (SIF) emission, fluorescence spectra, and hyperspectral features such as the red edge and the photochemical reflectance index (PRI) - can be used to greatly enhance the predictive power of global circulation models (GCMs) by providing better constraints on GPP. The way to use measured optical data to parameterize existing models such as SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes) is not trivial, however. We have therefore extended a biochemical model to include fluorescence and other parameters in a coupled treatment. To help parameterize the model, we then use nonlinear curve-fitting routines to determine the parameter set that enables model results to best fit leaf-level gas exchange and optical data measurements. To make the tool more accessible to all practitioners, we have further designed a graphical user interface (GUI) based front-end to allow researchers to analyze data with a minimum of effort while, at the same time, allowing them to change parameters interactively to visualize how variation in model parameters affect predicted outcomes such as photosynthetic rates, electron transport, and chlorophyll fluorescence. Here we discuss the tool and its effectiveness, using recently-gathered leaf-level data.

  4. Effects of salinity and nutrients on the growth and chlorophyll fluorescence of Caulerpa lentillifera

    Science.gov (United States)

    Guo, Hui; Yao, Jianting; Sun, Zhongmin; Duan, Delin

    2015-03-01

    Caulerpa lentillifera is a green algae that distributes worldwide and is cultivated for food. We assessed vegetative propagation of C. lentillifera by measuring the specific growth rate (SGR) and chlorophyll fluorescence of the green algae cultured at different salinities and nutrient levels. The results indicated that C. lentillifera can survive in salinities ranging from 20 to 50, and can develop at salinities of 30 to 40. The maximum SGR for C. lentillifera occurred at a salinity of 35. Both chlorophyll content and the ratio of variable to maximum fluorescence ( F v/ F m) were also at a maximum at a salinity of 35. Photosynthesis was inhibited in salinities greater than 45 and less than 25. Both the maximum SGR and maximum chlorophyll content were found in algae treated with a concentration of 0.5 mmol/L of NO3-N and 0.1 mmol/L of PO4-P. The photosynthetic capacity of photosystem II (PSII) was inhibited in cultures of C. lentillifera at high nutrient levels. This occurred when NO3-N concentrations were greater than 1.0 mmol/L and when PO4-P concentrations were at 0.4 mmol/L. As there is strong need for large-scale cultivation of C. lentillifera, these data contribute important information to ensure optimal results.

  5. From the shape of the vertical profile of in vivo fluorescence to Chlorophyll-a concentration

    Science.gov (United States)

    Mignot, A.; Claustre, H.; D'Ortenzio, F.; Xing, X.; Poteau, A.; Ras, J.

    2011-08-01

    In vivo fluorescence of Chlorophyll-a (Chl-a) is a potentially useful property to study the vertical distribution of phytoplankton biomass. However the technique is presently not fully exploited as it should be, essentially because of the difficulties in converting the fluorescence signal into an accurate Chl-a concentration. These difficulties arise noticeably from natural variations in the Chl-a fluorescence relationship, which is under the control of community composition as well as of their nutrient and light status. As a consequence, although vertical profiles of fluorescence are likely the most recorded biological property in the open ocean, the corresponding large databases are underexploited. Here with the aim to convert a fluorescence profile into a Chl-a concentration profile, we test the hypothesis that the Chl-a concentration can be gathered from the sole knowledge of the shape of the fluorescence profile. We analyze a large dataset from 18 oceanographic cruises conducted in case-1 waters from the highly stratified hyperoligotrophic waters (surface Chl-a = 0.02 mg m-3) of the South Pacific Gyre to the eutrophic waters of the Benguela upwelling (surface Chl-a = 32 mg m-3) and including the very deep mixed waters in the North Atlantic (Mixed Layer Depth = 690 m). This dataset encompasses more than 700 vertical profiles of Chl-a fluorescence as well as accurate estimations of Chl-a by High Performance Liquid Chromatography (HPLC). Two typical fluorescence profiles are identified, the uniform profile, characterized by a homogeneous layer roughly corresponding to the mixed layer, and the non-uniform profile, characterized by the presence of a Deep Chlorophyll Maximum. Using appropriate mathematical parameterizations, a fluorescence profile is subsequently represented by 3 or 5 shape parameters for uniform or non-uniform profiles, respectively. For both situations, an empirical model is developed to predict the "true" Chl-a concentration from these shape

  6. From the shape of the vertical profile of in vivo fluorescence to Chlorophyll-a concentration

    Directory of Open Access Journals (Sweden)

    J. Ras

    2011-08-01

    Full Text Available In vivo fluorescence of Chlorophyll-a (Chl-a is a potentially useful property to study the vertical distribution of phytoplankton biomass. However the technique is presently not fully exploited as it should be, essentially because of the difficulties in converting the fluorescence signal into an accurate Chl-a concentration. These difficulties arise noticeably from natural variations in the Chl-a fluorescence relationship, which is under the control of community composition as well as of their nutrient and light status. As a consequence, although vertical profiles of fluorescence are likely the most recorded biological property in the open ocean, the corresponding large databases are underexploited. Here with the aim to convert a fluorescence profile into a Chl-a concentration profile, we test the hypothesis that the Chl-a concentration can be gathered from the sole knowledge of the shape of the fluorescence profile. We analyze a large dataset from 18 oceanographic cruises conducted in case-1 waters from the highly stratified hyperoligotrophic waters (surface Chl-a = 0.02 mg m−3 of the South Pacific Gyre to the eutrophic waters of the Benguela upwelling (surface Chl-a = 32 mg m−3 and including the very deep mixed waters in the North Atlantic (Mixed Layer Depth = 690 m. This dataset encompasses more than 700 vertical profiles of Chl-a fluorescence as well as accurate estimations of Chl-a by High Performance Liquid Chromatography (HPLC. Two typical fluorescence profiles are identified, the uniform profile, characterized by a homogeneous layer roughly corresponding to the mixed layer, and the non-uniform profile, characterized by the presence of a Deep Chlorophyll Maximum. Using appropriate mathematical parameterizations, a fluorescence profile is subsequently represented by 3 or 5 shape parameters for uniform or non-uniform profiles, respectively. For both situations, an empirical model is developed to predict the "true" Chl-a concentration

  7. Potassium Iodide and Acrylamide Fluorescence Quenching Studies on Gamma-Crystallins of Human Lenses in Development and Aging

    Institute of Scientific and Technical Information of China (English)

    1992-01-01

    γ_1-γ_2-and γ_3-crystallin(corresponding to γs-,γC-and γD- crys-tallin respectively)of human fetal,2 year and 20~+ year old lenses areseparated by Sephadex gel chromatography.lodide and acrylamide are usedto quench the tryptophane fluorescence of sub-γ-crystalline fractions and Ksvand fa values are calculated.The results show that iodide has no clear quench-ing effects on all γ-crystallins,the quenching effects of acrylamide on the tryp-tophan fluorescences of γ1-γ2-and γ3-crystallin from lenses of the ...

  8. Hydrophobic Acceleration of Electron-Transfer Fluorescence Quenching Processes between Excited 1-Alkanoylperylenes and Ferrocene Derivatives

    Institute of Scientific and Technical Information of China (English)

    SHI, Ji-Liang

    2001-01-01

    Coaggregation-facilitated Electron-transfer (ET) fluorescence quenching processes between an excited 1-alkanoylperylene (Pe-n, n=4, 8, 12) as an acceptor and an 1-alkanoylferrocene (Fc-m, m=4, 8, 12, 16 ) or a 1,1-dialkanoyiferrocene (Fc-m-2, m=4, 8, 12, 16) as a donor have been investigated by means of fluorescence spectroscopy in dioxane (DX)H2O binary solvents of different φ values, where φ is the volume fraction of the organic component of an aquiorgano mixture. This is a first observation of an ET processes facilitated by hydrophobic-lipophilic interaction (HLI) with organometallic compounds as donors. Tne extent of HLI-driven coaggregation between the acceptor and the donor may be assessed from the efficiency of fluorescence quenching, i.e.,the slope B of Eq. ( 2 ). The chain-foldability effect and the intramolecular “self-satisfation” of HLI for Fc-m-2 have been observed. The experimental results show that the behavior of Fc-m as a quencher for fluorescence quenching of Pen* is rather similar to that of N-alkylsubstituend phenothiazine.

  9. Chlorophyll a fluorescence induction: a personal perspective of the thermal phase, the J-I-P rise.

    Science.gov (United States)

    Stirbet, Alexandrina; Govindjee

    2012-09-01

    The fast (up to 1 s) chlorophyll (Chl) a fluorescence induction (FI) curve, measured under saturating continuous light, has a photochemical phase, the O-J rise, related mainly to the reduction of Q(A), the primary electron acceptor plastoquinone of Photosystem II (PSII); here, the fluorescence rise depends strongly on the number of photons absorbed. This is followed by a thermal phase, the J-I-P rise, which disappears at subfreezing temperatures. According to the mainstream interpretation of the fast FI, the variable fluorescence originates from PSII antenna, and the oxidized Q(A) is the most important quencher influencing the O-J-I-P curve. As the reaction centers of PSII are gradually closed by the photochemical reduction of Q(A), Chl fluorescence, F, rises from the O level (the minimal level) to the P level (the peak); yet, the relationship between F and [Q(A) (-)] is not linear, due to the presence of other quenchers and modifiers. Several alternative theories have been proposed, which give different interpretations of the O-J-I-P transient. The main idea in these alternative theories is that in saturating light, Q(A) is almost completely reduced already at the end of the photochemical phase O-J, but the fluorescence yield is lower than its maximum value due to the presence of either a second quencher besides Q(A), or there is an another process quenching the fluorescence; in the second quencher hypothesis, this quencher is consumed (or the process of quenching the fluorescence is reversed) during the thermal phase J-I-P. In this review, we discuss these theories. Based on our critical examination, that includes pros and cons of each theory, as well mathematical modeling, we conclude that the mainstream interpretation of the O-J-I-P transient is the most credible one, as none of the alternative ideas provide adequate explanation or experimental proof for the almost complete reduction of Q(A) at the end of the O-J phase, and for the origin of the fluorescence

  10. Physiological responses of Brassica napus to fulvic acid under water stress: Chlorophyll a fluorescence and antioxidant enzyme activity

    Directory of Open Access Journals (Sweden)

    Ramin Lotfi

    2015-10-01

    Full Text Available The ameliorative effect of fulvic acid (0, 300, and 600 mg L− 1 on photosystem II and antioxidant enzyme activity of the rapeseed (Brassica napus L. plant under water stress (60, 100, and 140 mm evaporation from class A pan was studied using split plots in a randomized complete block design with three replications. Results indicated that application of fulvic acid (FA improved the maximum quantum efficiency of PSII (Fv/Fm and performance index (PI of plants under both well-watered and limited-water conditions. The time span from Fo to Fm and the energy necessary for the closure of all reaction centers was significantly increased, but the size of the plastoquinone pool was reduced with increasing water stress levels. Plants treated with FA had higher peroxidase and catalase activities under all irrigation conditions. Activities of ascorbate peroxidase and superoxide dismutase in plants increased with increasing water stress. Malondialdehyde increased under severe water stress, but application of FA significantly decreased lipid peroxidation. Production of reactive oxygen species (ROS is a common phenomenon in plants under stress. Under this condition, the balance between the production of ROS and the quenching activity of antioxidants is upset, often resulting in oxidative damage. In this study, application of FA significantly increased fluorescence of chlorophyll a, inhibiting ROS production and enhancing antioxidant enzymes activity that destroyed ROS. Thus, ROS in plant cells was reduced under water stress by application of FA and consequently lipid peroxidation was reduced.

  11. Physiological responses of Brassica napus to fulvic acid under water stress: Chlorophyll a fluorescence and antioxidant enzyme activity

    Institute of Scientific and Technical Information of China (English)

    Ramin; Lotfi; Mohammad; Pessarakli; Puriya; Gharavi-Kouchebagh; Hossein; Khoshvaghti

    2015-01-01

    The ameliorative effect of fulvic acid(0, 300, and 600 mg L-1) on photosystem II and antioxidant enzyme activity of the rapeseed(Brassica napus L.) plant under water stress(60, 100, and 140 mm evaporation from class A pan) was studied using split plots in a randomized complete block design with three replications. Results indicated that application of fulvic acid(FA) improved the maximum quantum efficiency of PSII(Fv/Fm)and performance index(PI) of plants under both well-watered and limited-water conditions. The time span from Foto Fmand the energy necessary for the closure of all reaction centers was significantly increased, but the size of the plastoquinone pool was reduced with increasing water stress levels. Plants treated with FA had higher peroxidase and catalase activities under all irrigation conditions. Activities of ascorbate peroxidase and superoxide dismutase in plants increased with increasing water stress. Malondialdehyde increased under severe water stress, but application of FA significantly decreased lipid peroxidation. Production of reactive oxygen species(ROS) is a common phenomenon in plants under stress. Under this condition, the balance between the production of ROS and the quenching activity of antioxidants is upset, often resulting in oxidative damage. In this study, application of FA significantly increased fluorescence of chlorophyll a, inhibiting ROS production and enhancing antioxidant enzymes activity that destroyed ROS. Thus, ROS in plant cells was reduced under water stress by application of FA and consequently lipid peroxidation was reduced.

  12. Physiological responses of Brassica napus to fulvic acid under water stress:Chlorophyll a fluorescence and antioxidant enzyme activity

    Institute of Scientific and Technical Information of China (English)

    Ramin Lotfi; Mohammad Pessarakli; Puriya Gharavi-Kouchebagh; Hossein Khoshvaghti

    2015-01-01

    The ameliorative effect of fulvic acid (0, 300, and 600 mg L−1) on photosystem II and antioxidant enzyme activity of the rapeseed (Brassica napus L.) plant under water stress (60, 100, and 140 mm evaporation from class A pan) was studied using split plots in a randomized complete block design with three replications. Results indicated that application of fulvic acid (FA) improved the maximum quantum efficiency of PSII (Fv/Fm) and performance index (PI) of plants under both well-watered and limited-water conditions. The time span from Fo to Fm and the energy necessary for the closure of all reaction centers was significantly increased, but the size of the plastoquinone pool was reduced with increasing water stress levels. Plants treated with FA had higher peroxidase and catalase activities under all irrigation conditions. Activities of ascorbate peroxidase and superoxide dismutase in plants increased with increasing water stress. Malondialdehyde increased under severe water stress, but application of FA significantly decreased lipid peroxidation. Production of reactive oxygen species (ROS) is a common phenomenon in plants under stress. Under this condition, the balance between the production of ROS and the quenching activity of antioxidants is upset, often resulting in oxidative damage. In this study, application of FA significantly increased fluorescence of chlorophyll a, inhibiting ROS production and enhancing antioxidant enzymes activity that destroyed ROS. Thus, ROS in plant cells was reduced under water stress by application of FA and consequently lipid peroxidation was reduced.

  13. [Effects of acid rain stress on Eleocarpus glabripetalus seedlings leaf chlorophyll fluorescence characteristics and growth].

    Science.gov (United States)

    Yin, Xiu-Min; Yu, Shu-Quan; Jiang, Hong; Liu, Mei-Hu

    2010-06-01

    A pot experiment was conducted to study the Eleocarpus glabripetalus seedlings leaf chlorophyll fluorescence characteristics and growth in different seasons under simulated acid rain stress (heavy, pH = 2. 5; moderate, pH = 4.0; and control, pH = 5.6). In the same treatments, the leaf relative chlorophyll content (SPAD), maximum PS II photochemical efficiency (F(v)/F(m)), actual PSII photochemical quantum yield (phi(PS II)), plant height, and stem diameter in different seasons were all in the order of October > July > April > January. In the same seasons, all the parameters were in the order of heavy acid rain > moderate acid rain > control. The interactions between different acid rain stress and seasons showed significant effects on the SPAD, F(v)/F(m), plant height, and stem diameter, but lesser effects on phi(PS II), qp and qN.

  14. [Effects of simulated acid rain on Quercus glauca seedlings photosynthesis and chlorophyll fluorescence].

    Science.gov (United States)

    Li, Jia; Jiang, Hong; Yu, Shu-quan; Jiang, Fu-wei; Yin, Xiu-min; Lu, Mei-juan

    2009-09-01

    Taking the seedlings of Quercus glauca, a dominant evergreen broadleaf tree species in subtropical area, as test materials, this paper studied their photosynthesis, chlorophyll fluorescence, and chlorophyll content under effects of simulated acid rain with pH 2.5, 4.0, and 5.6 (CK). After 2-year acid rain stress, the net photosynthetic rate of Q. glauca increased significantly with decreasing pH of acid rain. The acid rain with pH 2.5 and 4.0 increased the stomatal conductance and transpiration rate, and the effect was more significant under pH 2.5. The intercellular CO2 concentration decreased in the order of pH 2.5 > pH 5.6 > pH 4.0. The maximum photosynthetic rate, light compensation point, light saturation point, and dark respiration rate were significantly higher under pH 2.5 and 4.0 than under pH 5.6, while the apparent quantum yield was not sensitive to acid rain stress. The maximal photochemical efficiency of PS II and the potential activity of PS II under pH 2.5 and 4.0 were significantly higher than those under pH 5.6. The relative chlorophyll content was in the order of pH 2.5 > pH 5.6 > pH 4.0, and there was a significant difference between pH 2.5 and 4.0. All the results suggested that the photosynthesis and chlorophyll fluorescence of Q. glauca increased under the effects of acid rain with pH 2.5 and 4.0, and the acid rain with pH 2.5 had more obvious effects.

  15. Quenching of the intrinsic fluorescence of bovine serum albumin by chlorpromazine and hemin

    Directory of Open Access Journals (Sweden)

    Silva D.

    2004-01-01

    Full Text Available The binding of chlorpromazine (CPZ and hemin to bovine serum albumin was studied by the fluorescence quenching technique. CPZ is a widely used anti-psychotic drug that interacts with blood components, influences bioavailability, and affects function of several biomolecules. Hemin is an important ferric residue of hemoglobin that binds within the hydrophobic region of albumin with high specificity. Quenching of the intrinsic fluorescence of bovine serum albumin (BSA was observed by selectively exciting tryptophan residues at 290 nm. Emission spectra were recorded in the range from 300 to 450 nm for each quencher addition. Stern-Volmer graphs were plotted, and the quenching constant estimated for BSA solution titrated with hemin at 25ºC was 1.44 (± 0.05 x 10(5 M-1. Results showed that bovine albumin tryptophans are not equally accessible to CPZ, in agreement with the idea that polar or charged quenchers have more affinity for amino acid residues on the outer wall of the protein. Hemin added to albumin solution at a molar ratio of 1:1 quenched about 25% of their fluorescence. The quenching effect of CPZ on albumin-hemin solution was stronger than on pure BSA. This increase can be the result of combined conformational changes in the structure of albumin caused firstly by hemin and then by CPZ. Our results suggest that the primary binding site for hemin on bovine albumin may be located asymmetrically between the two tryptophans along the sequence formed by subdomains IB and IIA, closer to tryptophan residue 212.

  16. Femtosecond fluorescence spectra of tryptophan in human gamma-crystallin mutants: site-dependent ultrafast quenching.

    Science.gov (United States)

    Xu, Jianhua; Chen, Jiejin; Toptygin, Dmitri; Tcherkasskaya, Olga; Callis, Patrik; King, Jonathan; Brand, Ludwig; Knutson, Jay R

    2009-11-25

    The eye lens Crystallin proteins are subject to UV irradiation throughout life, and the photochemistry of damage proceeds through the excited state; thus, their tryptophan (Trp) fluorescence lifetimes are physiologically important properties. The time-resolved fluorescence spectra of single Trps in human gammaD- and gammaS-Crystallins have been measured with both an upconversion spectrophotofluorometer on the 300 fs to 100 ps time scale, and a time correlated single photon counting apparatus on the 100 ps to 10 ns time scale, respectively. Three Trps in each wild type protein were replaced by phenylalanine, leading to single-Trp mutants: W68-only and W156-only of HgammaD- and W72-only and W162-only of HgammaS-Crystallin. These proteins exhibit similar ultrafast signatures: positive definite decay associated spectra (DAS) for 50-65 ps decay constants that indicate dominance of fast, heterogeneous quenching. The quenched population (judged by amplitude) of this DAS differs among mutants. Trps 68, 156 in human gammaD- and Trp72 in human gammaS-Crystallin are buried, but water can reach amide oxygen and ring HE1 atoms through narrow channels. QM-MM simulations of quenching by electron transfer predict heterogeneous decay times from 50-500 ps that agree with our experimental results. Further analysis of apparent radiative lifetimes allow us to deduce that substantial subpopulations of Trp are fully quenched in even faster (sub-300 fs) processes for several of the mutants. The quenching of Trp fluorescence of human gammaD- and gammaS-Crystallin may protect them from ambient light induced photo damage.

  17. Cytokinin-induced changes in the chlorophyll content and fluorescence of in vitro apple leaves.

    Science.gov (United States)

    Dobránszki, Judit; Mendler-Drienyovszki, Nóra

    2014-10-15

    Cytokinins (CKs) are one of the main regulators of in vitro growth and development and might affect the developmental state and function of the photosynthetic apparatus of in vitro shoots. Effects of different cytokinin regimes including different types of aromatic cytokinins, such as benzyl-adenine, benzyl-adenine riboside and 3-hydroxy-benzyladenine alone or in combination were studied on the capacity of the photosynthetic apparatus and the pigment content of in vitro apple leaves after 3 weeks of culture. We found that the type of cytokinins affected both chlorophyll a and b contents and its ratio. Chlorophyll content of in vitro apple leaves was the highest when benzyl-adenine was applied as a single source of cytokinin in the medium (1846-2176 μg/1g fresh weight (FW) of the leaf). Increasing the concentration of benzyl-adenine riboside significantly decreased the chlorophyll content of the leaves (from 1923 to 1183 μg/1g FW). The highest chl a/chl b ratio was detected after application of meta-topolin (TOP) at concentrations of 2.0 and 6.0 μM (2.706 and 2.804). Chlorophyll fluorescence was measured both in dark-adapted (Fv/Fm test) and in light-adapted leaf samples (Yield test; Y(II)). The maximum quantum yield and efficiency of leaves depended on the cytokinin source of the medium varied between 0.683 and 0.861 (Fv/Fm) indicating a well-developed and functional photosynthetic apparatus. Our results indicate that the type and concentration of aromatic cytokinins applied in the medium affect the chlorophyll content of the leaves in in vitro apple shoots. Performance of the photosynthetic apparatus measured by chlorophyll fluorescence in the leaves was also modified by the cytokinin supply. This is the first ever study on the relationship between the cytokinin supply and the functionability of photosystem II in plant tissue culture and our findings might help to increase plantlet survival after transfer to ex vitro conditions.

  18. Fluorescence quenching of uric acid solubilized in bicontinuous microemulsion by nitrobenzene

    Directory of Open Access Journals (Sweden)

    Maurice O. Iwunze

    2013-02-01

    Full Text Available Abstract: Uric Acid is known to be practically insoluble in aqueous and alcoholic media. However, it exhibits a reasonable solubility in a Bicontinuous Microemulsion system – a 15-fold or more increase in solubility in this system compared to its solubility in water. The bicontinuous microemulsion is made up of three components –Dodecane-Surfactant-water. Uric acid solubilized in this system is quenched by nitrobenzene. The obtained fluorescence data do not obey the Stern-Volmer equation when plotted accordingly. Therefore, the modified Stern-Volmer equation was used to analyze the data. It was observed that only one third (1/3 of uric acid is accessible to quenching in this medium and the reaction is diffusion-limited. The Stern-Volmer quenching constant, KSV, was calculated to be 130 M-1 and the fluorescence lifetime, 0, the quantum yield,, and the bimolecular quenching rate constant, kq, were calculated as 10.6 nanoseconds, 0.06 and 1.231010 M-1s-1, respectively.

  19. Spectrofluorimetric determination of 5-fluorouracil by fluorescence quenching of 9-anthracenecarboxylic acid

    Science.gov (United States)

    Khot, M. S.; Bhattar, S. L.; Kolekar, G. B.; Patil, S. R.

    2010-09-01

    Photo-induced intermolecular electron transfer (PET) interaction between excited singlet (S 1) state of 9-anthracene carboxylic acid (9-ANCA) and DNA bases of pyrimidines as uracil and 5-fluorouracil (5-FU) has been studied in water and ethanol solutions using steady-state fluorescence spectroscopy. The intensity of all emission bands of 9-ANCA was quenched in presence of uracil and 5-FU by electron transfer reaction without formation of an exciplex. It was found that uracil and 5-fluorouracil acts as effective electron donors and simultaneously quench the fluorescence of electron-accepting sensitizer 9-ANCA. The quenching by diffusion-controlled rate coincides well with the dynamic Stern-Volmer correlation. The bimolecular quenching rate constant (kqss) and electron transfer rate constant ( ket) observed are seen to be much higher for 5-fluorouracil than those for uracil. The thermodynamic parameters estimated by using the Rehm-Weller equation were used to propose a suitable mechanism for PET occurring between uracils and 9-ANCA. The proposed method was used to determine 5-fluorouracil from pharmaceutical samples with satisfactory results. The technique is more selective, sensitive and relatively free from coexisting substances.

  20. Fluorescence quenching as a tool to investigate quinolone antibiotic interactions with bacterial protein OmpF.

    Science.gov (United States)

    Neves, Patrícia; Sousa, Isabel; Winterhalter, Mathias; Gameiro, Paula

    2009-02-01

    The outer membrane porin OmpF is an important protein for the uptake of antibiotics through the outer membrane of gram-negative bacteria; however, the possible binding sites involved in this uptake are still not recognized. Determination, at the molecular level, of the possible sites of antibiotic interaction is very important, not only to understand their mechanism of action but also to unravel bacterial resistance. Due to the intrinsic OmpF fluorescence, attributed mainly to its tryptophans (Trp(214), Trp(61)), quenching experiments were used to assess the site(s) of interaction of some quinolone antibiotics. OmpF was reconstituted in different organized structures, and the fluorescence quenching results, in the presence of two quenching agents, acrylamide and iodide, certified that acrylamide quenches Trp(61) and iodide Trp(214). Similar data, obtained in presence of the quinolones, revealed distinct behaviors for these antibiotics, with nalidixic acid interacting near Trp(214) and moxifloxacin near Trp(61). These studies, based on straightforward and quick procedures, show the existence of conformational changes in the protein in order to adapt to the different organized structures and to interact with the quinolones. The extent of reorganization of the protein in the presence of the different quinolones allowed an estimate on the sites of protein/quinolone interaction.

  1. Varietal differences in photosynthetic characters and chlorophyll fluorescence induction kinetics parameters among intergeneric progeny derived from Oryza×Sorghum, its parents, and hybrid rice

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A comparative study on the photosynthetic parameters among intergeneric progenies derived from Oryza sativa L.×Sorghum vulgare L., its maternal parent Gui 630 and commercial 3-line hybrid rice Shanyou 63 in pot experiment in greenhouse was conducted. The morphological and photosynthetic characters of canopy leaves and chlorophyll fluorescence kinetic parameters including Fv/Fm, Fv/F0, photochemical quenching coefficient and non-photochemical coefficient of canopy leaves of 3 varieties were measured. The results showed the progeny, Yuanyou 1, derived from an intergeneric cross of rice and sorghum possesses better canopy spatial architecture with thicker, heavier and bigger canopy leaf than its maternal parent Gui 630. Higher photosynthetic rate due to higher chlorophyll content, higher primary energy transformation efficiency, potential of PSII and non-photochemical quenching coefficient (qE) were also measured in Yuanyou 1. These explain partly why the intergeneric progeny has higher biomass production, and better tolerance to adverse conditions and higher field yields even under stress conditions.

  2. Varietal differences in photosynthetic characters and chlorophyll fluorescence induction kinetics parameters among intergeneric progeny derived from Oryza×Sorghum, its parents, and hybrid rice

    Institute of Scientific and Technical Information of China (English)

    KatsuyoshiShimizu; 唐建军; 陈欣

    2002-01-01

    A comparative study on the photosynthetic parameters among intergeneric progenies derived from Oryza sativa L.× Sorghum vulgare L. , its maternal parent Gui 630 and commercial 3-line hybrid rice Shanyou 63 in pot experiment in greenhouse was conducted. The morphological and photosynthetic characters of canopy leaves and chlorophyll fluorescence kinetic pm'mneters including Fv/Fm, Fv/F0, photochemical quenching coefficient and non-photochemical coefficient of canopy leaves of 3 varieties were measured. The results showed the progeny, Yuanyou 1, derived from an intergeneric cross of rice and sorghum possesses better canopy spatial architecture with thicker, heavier and bigger canopy leaf than its maternal parent Gui 630.Higher photosynthetic rate due to higher chlorophyll content, higher primary energy transformation efficiency,potential of PSII and non-photochemieal quenching coefficient (qE) were also measured in Yuanyou 1. These explain partly why the intergeneric progeny has higher biomass production, and better tolerance to adverse conditions and higher field yields even under stress conditions.

  3. Electronic interactions of i, i + 1 dithioamides: increased fluorescence quenching and evidence for n-to-π* interactions.

    Science.gov (United States)

    Huang, Yun; Ferrie, John J; Chen, Xing; Zhang, Yitao; Szantai-Kis, D Miklos; Chenoweth, David M; Petersson, E James

    2016-06-14

    Thioamide residues can be effective, minimally-perturbing fluorescence quenching probes for studying protein folding and proteolysis. In order to increase the level of quenching, we have here explored the use of adjacent dithioamides. We have found that they are more effective fluorescence quenchers, as expected, but we have also observed unexpected changes in the thioamide absorption spectra that may arise from n-to-π* interactions of the thiocarbonyls. We have made use of the increased quenching to improve the fluorescence turn-on of thioamide protease sensors.

  4. Quenching of tryptophan fluorescence of bovine serum albumin under the effect of ions of heavy metals

    Science.gov (United States)

    Plotnikova, O. A.; Mel'nikov, A. G.; Mel'nikov, G. V.; Gubina, T. I.

    2016-01-01

    The interaction of heavy metals with bovine serum albumin (BSA) has been studied using data of quenching of intrinsic fluorescence of the protein by the ions of the heavy metals. Under the assumption of static quenching with formation of nonfluorescent complexes of fluorophores of BSA with heavy metals, conclusions have been drawn on the peculiarities of binding of the heavy metals to the protein. The values of the Stern-Volmer constants of association and those of the constants of BSA binding to the heavy metals decrease in the order Cu(II) > Pb(II) > Cd(II). It has been experimentally found that the copper ions have greater capacity to bind to the protein with the formation of the nonfluorescent complexes, which results in a significant decrease in the fluorescence intensity of the protein.

  5. Quantitative genetic analysis of chlorophyll a fluorescence parameters in maize in the field environments

    Institute of Scientific and Technical Information of China (English)

    Domagojimi; Hrvoje Lepedu; Vlatka Jurkovi; Jasenka Antunovi; Vera Cesar

    2014-01-01

    Chlorophyl fluorescence transient from initial to maximum fluorescence (“P”step) throughout two intermedi-ate steps (“J”and“I”) (JIP-test) is considered a reliable early quantitative indicator of stress in plants. The JIP-test is particularly useful for crop plants when applied in variable field environments. The aim of the present study was to conduct a quantitative trait loci (QTL) analysis for nine JIP-test parameters in maize during flowering in four field environ-ments differing in weather conditions. QTL analysis and identification of putative candidate genes might help to explain the genetic relationship between photosynthesis and different field scenarios in maize plants. The JIP-test param-eters were analyzed in the intermated B73 ? Mo17 (IBM) maize population of 205 recombinant inbred lines. A set of 2,178 molecular markers across the whole maize genome was used for QTL analysis revealing 10 significant QTLs for seven JIP-test parameters, of which five were co-localized when combined over the four environments indicating polygenic inheritance and pleiotropy. Our results demonstrate that QTL analysis of chlorophyl fluorescence parameters was capable of detecting one pleiotropic locus on chromosome 7, coinciding with the gene gst23 that may be associated with efficient photosynthe-sis under different field scenarios.

  6. Fluorescence imaging and chlorophyll fluorescence to evaluate the role of EDU in UV-B protection in cucumber

    Science.gov (United States)

    Sandhu, Ravinder K.; Kim, Moon S.; Krizek, Donald T.; Middleton, Elizabeth M.

    1997-07-01

    A fluorescence imaging system and chlorophyll fluorescence emissions were used to evaluate whether EDU, N-[2-(2-oxo-1- imidazolidinyl) ethyl]-N'-phenylurea, provided protection against ultraviolet-B (UV-B) irradiation (290 - 320 nm) in cucumber (Cucumis sativus L.) leaves. Plants were grown in growth chambers illuminated for 14 h per day with 400 W high pressure sodium and metal halide lamps. Photosynthetically active radiation (PAR) for 1 hr at the beginning and end of each cycle was provided at 270 micrometers ol m-2 s-1 PAR; during the other 12 hr of the photoperiod, the plants received 840 micrometers ol m-2 s-1 PAR. Beginning on the twelfth day, the plants were exposed to UV-B radiation (0.2 & 18.0 kJ m-2d-1) for 2 days at 8 h per day centered in the photoperiod. Rapidly acquired (less than 1 s), high spatial resolution (less than 1 mm2) images were obtained for whole adaxial leaf surfaces using a fluorescence imaging system. The steady-state fluorescence images were acquired in four spectral regions: blue (F450 nm), green (F550 nm), red (F680 nm), and far-red (F740 nm). Fluorescence emission spectra for leaf pigments extracted in dimethyl sulfoxide (DMSO) were obtained by excitation at 280 and 380 nm (280EX 300 - 530 nm; 380EX 400 - 800 nm). Both UV-B and EDU induced stress responses in cucumber leaves that altered the fluorescence emissions obtained from extracts. In the fluorescence images only UV-B induced stress responses were observed but this damage was detected before it was visually apparent. There was no evidence that EDU afforded protection against UV-B irradiation. Use of fluorescence imaging may provide an early stress detection capability for helping to assess damage to the photosynthetic apparatus of plants.

  7. An Intelligent Optical Dissolved Oxygen Measurement Method Based on a Fluorescent Quenching Mechanism

    Directory of Open Access Journals (Sweden)

    Fengmei Li

    2015-12-01

    Full Text Available Dissolved oxygen (DO is a key factor that influences the healthy growth of fishes in aquaculture. The DO content changes with the aquatic environment and should therefore be monitored online. However, traditional measurement methods, such as iodometry and other chemical analysis methods, are not suitable for online monitoring. The Clark method is not stable enough for extended periods of monitoring. To solve these problems, this paper proposes an intelligent DO measurement method based on the fluorescence quenching mechanism. The measurement system is composed of fluorescent quenching detection, signal conditioning, intelligent processing, and power supply modules. The optical probe adopts the fluorescent quenching mechanism to detect the DO content and solves the problem, whereas traditional chemical methods are easily influenced by the environment. The optical probe contains a thermistor and dual excitation sources to isolate visible parasitic light and execute a compensation strategy. The intelligent processing module adopts the IEEE 1451.2 standard and realizes intelligent compensation. Experimental results show that the optical measurement method is stable, accurate, and suitable for online DO monitoring in aquaculture applications.

  8. Synthesis, characterization and fluorescence quenching of conjugated polymer containing triphenylamine group

    Institute of Scientific and Technical Information of China (English)

    Feng LIU; Jianhua XIAO; Weihua REN; Jun HU; Honglai LIU

    2008-01-01

    Poly(triphenylamine-p-phenylenevinylene)s with two different end-groups were obtained through a Wittig polycondensation. The structures of two copoly-mers were characterized. Ultraviolet and visible spectro-scopy (UV-Vis) and photoluminescence (PL) spectra show the end-capped polymer emits intensive green light in both solution and film state. Their applications in the detection of nitro compounds were investigated, and the results show high fluorescence quenching sensitivity of the end-capped polymer towards o-nitrotoluene (o-NT). When the concentration of o-NT was 21.5×10-3 mol/L, the fluorescence quenching reached 96%. Additionally, after the exposure of polymer film in three different quenchers such as dinitrotoluene (DNT), p-nitrobenzo-quinone (p-BQ) and p-nitrotoluene (p-NT) for 600 s, its fluorescence quenching reached 93.6%, 11.5% and 77.9%, respectively. This kind of polymer has great advantages in preparation and may find applications in the detection of nitro explosives.

  9. The fluorescence quenching mechanism of coumarin 120 with CdS nanoparticles in aqueous suspension

    Energy Technology Data Exchange (ETDEWEB)

    Acar, Murat; Bozkurt, Ebru; Meral, Kadem; Arık, Mustafa; Onganer, Yavuz, E-mail: yonganer@atauni.edu.tr

    2015-01-15

    The interaction of coumarin 120 (C120) with CdS nanoparticles (CdS NPs) in aqueous suspension was examined by using UV–vis absorption, steady-state, time-resolved fluorescence, and electron paramagnetic resonance (EPR) spectroscopy techniques. The fluorescence intensity of C120 was quenched with increasing the amount of CdS NPs in the aqueous suspension. The spectroscopic data revealed that the C120 molecules adsorbed on CdS NPs via electrostatic interactions. The apparent association constant (K{sub app}) and the degree of association (α) for C120/CdS NPs were determined as 130.3 M{sup −1} and 0.51 for 4 nm CdS NPs and 624.3 M{sup −1} and 0.71 for 8 nm CdS NPs, respectively. The photoinduced EPR studies exhibited that no electron transfers between CdS and C120 taking place. The results revealed that the fluorescence quenching of C120 with different CdS NPs is due to the formation of a non-fluorescent complex. - Highlights: • Interaction of C120 with CdS NPs in aqueous solution was spectroscopically examined. • Nonfluorescent C120–CdS NPs complexes in aqueous solution were formed. • In the system, CdS NPs in aqueous solution acted as a fluorescence quencher.

  10. Determination of sunset yellow in soft drinks based on fluorescence quenching of carbon dots

    Science.gov (United States)

    Yuan, Yusheng; Zhao, Xin; Qiao, Man; Zhu, Jinghui; Liu, Shaopu; Yang, Jidong; Hu, Xiaoli

    2016-10-01

    Fluorescent carbon dots was prepared by heating N-(2-hydroxyethyl)ethylene diaminetriacetic acid in air. The carbon dots were not only highly soluble in water but also uniform in size, and possessed strong blue fluorescence and excitation wavelength-dependent emission properties with the maximum excitation and emission wavelength at 366 nm and 423 nm, respectively. Food colorant sunset yellow whose excitation and emission wavelength at 303 nm and 430 nm could selectively quench the fluorescence of carbon dots, efficient fluorescent resonance energy transfer between the carbon dots and sunset yellow is achieved. This was exploited to design a method for the determination of sunset yellow in the concentration range from 0.3 to 8.0 μmol L- 1, with a limit of detection (3 σ/k) of 79.6 nmol L- 1. Furthermore the fluorimetric detection method was established and validated for sunset yellow in soft drinks samples with satisfactory results.

  11. Relationship between the Fluorescence Lifetime of Chlorophyll 'a' and Primary Productivity within the Mississippi River Plume and Adjacent Shelf Region

    Science.gov (United States)

    Hall, Callie; Miller, Richard L.; Fernandez, Salvador M.; McKee, Brent A.

    2000-01-01

    In situ measurements of chlorophyll fluorescence intensity have been widely used to estimate phytoplankton biomass. However, because the fluorescence quantum yield of chlorophyll a in vivo can be highly variable, measurements of chlorophyll fluorescence intensity cannot be directly correlated with phytoplankton biomass and do not provide information on the physiological state of the phytoplankton under study. Conversely, lifetime-based measurements of chlorophyll fluorescence provide a framework in which photosynthetic rates of phytoplankton can be analyzed according to phytoplankton physiology. Along with the measurement of primary production and ambient nutrient concentrations within the Mississippi River plume in the northern Gulf of Mexico, phytoplankton fluorescence lifetimes were measured using a Fluorescence Lifetime Phytoplankton Analyzer (developed under a NASA Small Business Innovative Research contract to Ciencia, Inc.). Variability of fluorescence lifetimes within the plume can be used as a background from which to interpret variations in the maximum quantum yield of photochemistry. The extent to which nutrient and effluent loading in this dynamic coastal area affect the photosynthetic performance of phytoplankton will be presented as a function of phytoplankton fluorescence lifetimes.

  12. Relationship between the Fluorescence Lifetime of Chlorophyll 'a' and Primary Productivity within the Mississippi River Plume and Adjacent Shelf Region

    Science.gov (United States)

    Hall, Callie; Miller, Richard L.; Fernandez, Salvador M.; McKee, Brent A.

    2000-01-01

    In situ measurements of chlorophyll fluorescence intensity have been widely used to estimate phytoplankton biomass. However, because the fluorescence quantum yield of chlorophyll a in vivo can be highly variable, measurements of chlorophyll fluorescence intensity cannot be directly correlated with phytoplankton biomass and do not provide information on the physiological state of the phytoplankton under study. Conversely, lifetime-based measurements of chlorophyll fluorescence provide a framework in which photosynthetic rates of phytoplankton can be analyzed according to phytoplankton physiology. Along with the measurement of primary production and ambient nutrient concentrations within the Mississippi River plume in the northern Gulf of Mexico, phytoplankton fluorescence lifetimes were measured using a Fluorescence Lifetime Phytoplankton Analyzer (developed under a NASA Small Business Innovative Research contract to Ciencia, Inc.). Variability of fluorescence lifetimes within the plume can be used as a background from which to interpret variations in the maximum quantum yield of photochemistry. The extent to which nutrient and effluent loading in this dynamic coastal area affect the photosynthetic performance of phytoplankton will be presented as a function of phytoplankton fluorescence lifetimes.

  13. Violet diode laser-induced chlorophyll fluorescence: a tool for assessing mosaic disease severity in cassava (Manihot esculenta Crantz) cultivars.

    Science.gov (United States)

    Anderson, Benjamin; Eghan, Moses J; Asare-Bediako, Elvis; Buah-Bassuah, Paul K

    2012-01-01

    Violet diode laser-induced chlorophyll fluorescence was used in agronomical assessment (disease severity and average yield per plant). Because cassava (Manihot esculenta Crantz) is of economic importance, improved cultivars with various levels of affinity for cassava mosaic disease were investigated. Fluorescence data correlated with cassava mosaic disease severity levels and with the average yield per plant.

  14. A Dioxobilin-Type Fluorescent Chlorophyll Catabolite as a Transient Early Intermediate of the Dioxobilin-Branch of Chlorophyll Breakdown in Arabidopsis thaliana.

    Science.gov (United States)

    Süssenbacher, Iris; Hörtensteiner, Stefan; Kräutler, Bernhard

    2015-11-09

    Chlorophyll breakdown in higher plants occurs by the so called "PaO/phyllobilin" path. It generates two major types of phyllobilins, the characteristic 1-formyl-19-oxobilins and the more recently discovered 1,19-dioxobilins. The hypothetical branching point at which the original 1-formyl-19-oxobilins are transformed into 1,19-dioxobilins is still elusive. Here, we clarify this hypothetical crucial transition on the basis of the identification of the first natural 1,19-dioxobilin-type fluorescent chlorophyll catabolite (DFCC). This transient chlorophyll breakdown intermediate was isolated from leaf extracts of Arabidopsis thaliana at an early stage of senescence. The fleetingly existent DFCC was then shown to represent the direct precursor of the major nonfluorescent 1,19-dioxobilin that accumulated in fully senescent leaves.

  15. Fluorescence Quenching Nanoprobes Dedicated to In Vivo Photoacoustic Imaging and High-Efficient Tumor Therapy in Deep-Seated Tissue.

    Science.gov (United States)

    Qin, Huan; Zhou, Ting; Yang, Sihua; Xing, Da

    2015-06-10

    Photoacoustic imaging (PAI) and photoacoustic (PA) therapy have promising applications for treating tumors. It is known that the utilization of high-absorption-coefficient probes can selectively enhance the PAI target contrast and PA tumor therapy efficiency in deep-seated tissue. Here, the design of a probe with the highest availability of optical-thermo conversion by using graphene oxide (GO) and dyes via π-π stacking interactions is reported. The GO serves as a base material for loading dyes and quenching dye fluorescence via fluorescence resonance energy transfer (FRET), with the one purpose of maximum of PA efficiency. Experiments verify that the designed fluorescence quenching nanoprobes can produce stronger PA signals than the sum of the separate signals generated in the dye and the GO. Potential applications of the fluorescence quenching nanoprobes are demonstrated, dedicating to enhance PA contrast of targets in deep-seated tissues and tumors in living mice. PA therapy efficiency both in vitro and in vivo by using the fluorescence quenching nanoprobes is found to be higher than with the commonly used PA therapy agents. Taken together, quenching dye fluorescence via FRET will provide a valid means for developing high-efficiency PA probes. Fluorescence quenching nanoprobes are likely to become a promising candidate for deep-seated tumor imaging and therapy.

  16. Evaluation of Chlorophyll Content and Fluorescence Parameters as Indicators of Drought Tolerance in Barley

    Institute of Scientific and Technical Information of China (English)

    LI Rong-hua; GUO Pei-guo; Michael Baum; Stefania Grando; Salvatore Ceccarelli

    2006-01-01

    Drought is a major abiotic stress that severely affects food production worldwide. Agronomic and physiological traits associated with drought tolerance are suitable indicators for selection of drought tolerance genotypes to reduce the impact of water deficit on crop yield in breeding program. The objective of this study was to identify indicators related to drought tolerance through analysis of photosynthetic traits in barley (Hordeum vulgare L.). These traits included chlorophyll content, initial fluorescence (Fo), maximum primary yield of photochemistry of pho tosystem Ⅱ (Fv / Fo) and maximum quantum yield of photosystem Ⅱ (Fv/Fm). Four genotypes (Tadmor, Arta, Morocco9-75 and WI2291) variable in drought tolerance were used to investigate the correlation between these traits and drought tolerance. The results reflected that all of these traits were affected negatively in the four genotypes at different levels of post-anthesis drought stress, but the decrease in drought tolerant genotypes was much less than that of drought sensitive genotypes. The results further revealed that the components of the photosynthetic apparatus could be damaged significantly in drought sensitive genotypes, while drought tolerant genotypes were relatively less affected. On the other hand, the values of chlorophyll content, Fo, Fv/Fo and Fv/Fm in drought tolerance genotypes were significantly higher than those in drought sensitive genotypes under drought stress. It was concluded that chlorophyll content, Fo, Fv / Fo and Fv / Fm could be considered as reliable indicators in screening barley germplasm for drought tolerance.

  17. Fluorescence Quenching Study on the Interaction of Some Schiff Base Complexes with Bovine Serum Albumin

    Institute of Scientific and Technical Information of China (English)

    MEI,Ping; ZHANG,Li-Xia; LIU,Yi; CAI,Li-Hua; HU,Pei-Zhi

    2008-01-01

    The interaction of Schiff base ligand A and its three metal complexes[A-Fe(Ⅱ), A-Cu(Ⅱ), and A-Zn(Ⅱ)] with bovine serum albumin (BSA) was investigated using a tryptophan fluorescence quenching method. The Schiff base ligand A and its three metal complexes all showed quenching of BSA fluorescence in a Tris-HCl buffer. Quenching constants were determined for quenching BSA by the Schiff base ligand A and its metal complexes in a Tris-HCl buffer (pH=7.4) at different temperatures. The experimental results show that the dynamic quenching constant (KSV) was increased with increasing temperature, whereas the association constant (K) was decreased with the in crease of temperature. The thermodynamic parameters ΔH, ΔG and ΔS at different temperatures were calculated.The ionic strength of the Tris-HCl buffer had a great influence on the wavelength of maximum emission of BSA.Under low ionic strength, the emission spectra of BSA influenced by A-Zn(Ⅱ) had a small blue shift. Compared to A-Zn(Ⅱ), the emission spectra of BSA in the presence of the Schiff base ligand A and A-Cu(Ⅱ) had no significant λem shift. At high ionic strength, the emission spectra of BSA upon addition of the Schiff base A, A-Fe(Ⅱ), and A-Zn(Ⅱ) all had a red shift, but the emission spectra of BSA had λem shift neither at low ionic strength, nor at high ionic strength in the presence of A-Cu(Ⅱ). Furthermore, the temperature did not affect the λem shift of BSA emission spectra.

  18. Binding of caffeine with caffeic acid and chlorogenic acid using fluorescence quenching, UV/vis and FTIR spectroscopic techniques.

    Science.gov (United States)

    Belay, Abebe; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2016-03-01

    The interactions of caffeine (CF) with chlorogenic acid (CGA) and caffeic acid (CFA) were investigated by fluorescence quenching, UV/vis and Fourier transform infrared (FTIR) spectroscopic techniques. The results of the study indicated that the fluorescence quenching between caffeine and hydroxycinnamic acids could be rationalized in terms of static quenching or the formation of non-fluorescent CF-CFA and CF-CGA complexes. From fluorescence quenching spectral analysis, the quenching constant (KSV), quenching rate constant (kq), number of binding sites (n), thermodynamic properties and conformational changes of the interaction were determined. The quenching constants (KSV) between CF and CGA, CFA are 1.84 × 10(4) and 1.04 × 10(4) L/mol at 298 K and their binding site n is ~ 1. Thermodynamic parameters determined using the Van't Hoff equation indicated that hydrogen bonds and van der Waal's forces have a major role in the reaction of caffeine with caffeic acid and chlorogenic acid. The 3D fluorescence, UV/vis and FTIR spectra also showed that the binding of CF with CFA and CGA induces conformational changes in CFA and CGA.

  19. Chlorophyll a Fluorescence in Evaluation of the Effect of Heavy Metal Soil Contamination on Perennial Grasses

    Science.gov (United States)

    Żurek, Grzegorz; Rybka, Krystyna; Pogrzeba, Marta; Krzyżak, Jacek; Prokopiuk, Kamil

    2014-01-01

    Chlorophyll a fluorescence gives information about the plant physiological status due to its coupling to the photosynthetic electron transfer chain and to the further biochemical processes. Environmental stresses, which acts synergistically, disturbs the photosynthesis. The OJIP test, elaborated by Strasser and co-workers, enables comparison of the physiological status of plants grown on polluted vs. control areas. The paper shows that the Chl a measurements are very useful tool in evaluating of heavy metal ions influence on perennial grasses, tested as potential phytoremediators. Among 5 cultivars tested, the highest concentration of Cd and Zn ions, not associated with the yield reduction, was detected in the biomass of tall fescue cv. Rahela. Chl a fluorescence interpreted as double normalized curves pointed out Rahela as the outstanding cultivar under the HM ions stress. PMID:24633293

  20. Modified in situ antimicrobial susceptibility testing method based on cyanobacteria chlorophyll a fluorescence.

    Science.gov (United States)

    Heliopoulos, Nikolaos S; Galeou, Angeliki; Papageorgiou, Sergios K; Favvas, Evangelos P; Katsaros, Fotios K; Stamatakis, Kostas

    2016-02-01

    The chlorophyll a fluorescence based antimicrobial susceptibility testing (AST) method presented in a previous work was based on the measurement of Chl a fluorescence of the gram(-) cyanobacterium Synechococcus sp. PCC 7942. Synechococcus sp. PCC 7942 as a gram(-) bacterium is affected by antibacterial agents via mechanisms affecting all gram(-) bacteria, however, as an exclusively phototrophic organism it would also be affected by photosynthesis inhibitory action of an agent that otherwise has no antibacterial properties. In this report, the method is modified by replacing the exclusively phototrophic Synechococcus sp. PCC 7942 with the Synechocystis sp. PCC 6714, capable of both phototrophic and heterotrophic growth in order to add versatility and better reflect the antibacterial effects of surfaces under study towards nonphotosynthetic bacteria. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. [Photosynthetic functions and chlorophyll fast fluorescence characteristics of five Pinus species].

    Science.gov (United States)

    Qiu, Nian-Wei; Zhou, Feng; Gu, Zhu-Jun; Jia, Shu-Qin; Wang, Xing-An

    2012-05-01

    A comparative study was made on the needle morphological characteristics, photosynthetic rate, and chlorophyll fast fluorescence induction curves of five representative Pinus species P. parvifiora, P. armandii, P. bungeana, P. tabuliformis, and P. densiflora. Significant differences were observed in the needle morphological characteristics among the five species. P. tabuliformis had the longest needle length and highest needle density, whereas P. bungeana had the highest chlorophyll content. P. densiflora and P. parvifiora had the maximum and minimum photosynthetic rate, respectively. There was a positive correlation between the photosynthetic rate and stomatal conductance across the five species. The differences in the chlorophyll fast fluorescence induction curves of the five species were mainly manifested in J-step and I-step. Although the five species had similar values of Fv/Fm, Fv/Fo and Tfm, P. parviflora had significantly higher values of dV/dt(o), dVG/d(o), V and Vi, but lower energy flux ratio psi(o), phiEo and phiRo, compared with the other four species. The low PSII activity and efficiency of P. parviflora might relate to its smallest Sm, Sm/Tfm and N. P. densiflora and P. parvifiora had the maximum and minimum vitality indices PI(ABS/CSo/CSm) and DF, respectively, and there existed significant positive correlations between the PI(CSo) and PI(CSm) and the net photosynthetic rate of the five species, suggesting that PI(CSo) and PI(CSm) could be used to estimate the photosynthetic activity of Pinus trees.

  2. Choline-induced selective fluorescence quenching of acetylcholinesterase conjugated Au@BSA clusters.

    Science.gov (United States)

    Mathew, Meegle S; Baksi, Ananya; Pradeep, T; Joseph, Kuruvilla

    2016-07-15

    We have developed a highly selective sensitive fluorescent detection of acetylcholine (ACh) using bovine serum albumin (BSA) protected atomically precise clusters of gold. The gold quantum clusters (AuQC@BSA) synthesized using bovine serum albumin and conjugated with acetylcholinesterase (AChE), an enzyme specific for acetylcholine, resulting in AuQC@BSA-AChE. The enzyme, AChE hydrolyzes acetylcholine (ACh) to choline (Ch) which in turn interacts with AuQC@BSA-AChE and quenches its fluorescence, enabling sensing. We have carried out the real time monitoring of the hydrolysis of ACh using electrospray ionization mass spectrometry (ESI MS) to find out the mechanism of fluorescent quenching. The validity of present method for determination of concentration of acetylcholine in real system such as blood was demonstrated. Further, the sensor, AuQC@BSA-AChE can be easily coated on paper and an efficient and cheap sensor can be developed and detection limit for ACh is found to be 10nM. The fluorescent intensity of AuQC@BSA-AChE is sensitive towards acetylcholine in range of 10nM to 6.4µM. This suggests that AuQC@BSA-AChE has an excellent potential to be used for diagnosis of various neuropsychological and neuropsychiatric disorders.

  3. Changes in Chlorophyll Fluorescence of Rice Mutants Induced by High Hydrostatic Pressure

    Institute of Scientific and Technical Information of China (English)

    BAI Cheng-ke; LI Gui-shuang; PENG Chang-lian; DUAN Jun

    2003-01-01

    Three mutants of rice (Oryza sativa L. ), Mutant 1, Mutant 2and Mutant 3, which were selected by high hydrostatic pressure (75 MPa), and their parent Yuexiangzhan were used to study the changes in chlorophyll fluorescence during different growth stages. In all the three mutants, the function of PSⅡ was improved, Fy/Fm ratio of mutants increased compared to their parent at tillering and heading stage, and φPS Ⅱ also improved except for Mutant 2 at heading stage. Similar to their parent, the mutants exhibited slight photoinhibition at noon and almost complete recovery to initial levels of 6:00 after 18:00 at heading stage. At milking stage, the photoinhibition in the mutants was obvious, and recovered rapidly compared to the parent. Yields of individual plant and grain/straw ratio were also higher in three mutants than the parent. Results indicated that characteristics of chlorophyll fluorescence in leaves of mutants and their photoinhibition in the field had changed. It is suggested that high hydrostatic pressure induction could be applied as a new effective approach in high-yield rice breeding in the future.

  4. [Effects of exogenous Ca2+ on morphological and photosynthetic characteristics and chlorophyll fluorescent parameters of squash seedlings under high temperature and strong light stress].

    Science.gov (United States)

    Qin, Shu-hao; Li, Ling-ling; Chen, Na-na

    2010-11-01

    Taking squash (Cucurbita pepo L.) variety Alan as test object, this paper studied the effects of exogenous Ca2+ on the morphological and photosynthetic characteristics and chlorophyll fluorescent parameters of squash seedlings under the cross-stress of high temperature and strong light. Under the stress, applying 5-20 mmol x L(-1) of Ca2+ increased the plant height, leaf area, chlorophyll and carotenoid contents, photosynthetic rate (Pn), stoma conductance (Gs), transpiration rate (Tr), maximal PS II efficiency (Fv/Fm), actual PS II efficiency (phi(PS II)), and photochemical queching coefficient (q(P)), and decreased the intercellular CO2 concentration (Ci) and non-photochemical fluorescence quenching coefficient (NPQ), suggesting that this application of exogenous Ca2+ could effectively mitigate the damage of high temperature and strong light stress on the squash seedlings leaf, and make it keep more rapid photosynthetic electron transfer rate and higher PS II electron transfer activity. Among the treatments of applying Ca2+, 10 mmol Ca2+ x L(-1) had the best effect. When the Ca2+ application rate exceeded 40 mmol x L(1), no mitigation effect was observed on the high temperature and strong light stress.

  5. Characterization and application of PBA fiber optic chemical film sensor based on fluorescence multiple quenching

    Institute of Scientific and Technical Information of China (English)

    陈坚; 李伟; 阎超; 袁立懋; 郭炬亮; 周新继

    1997-01-01

    The three types of structure of the pyrenebutyric acid of fiber optic chemical film sensor were stud-ied by fluorescence multiple quenching. They are, for different test samples and purposes, respectively general, three-way and combined. A tri-cup method was designed to demonstrate the multiple quenching of response mechanism, and a relationship formula of mathematical approach was established. The response mechanism was shown to include the dynamic quenching , inner-filter effects and/or resonance energy transfer. To show the response characterization in a series of organic and inorganic quenchers, a new concept of apparent quenching coefficient Kq was advanced. This kind of sensor has been used in continuous and in situ monitoring of the dissolution rate of drug tablets, on line and in situ monitoring of some organic therapeutic drugs in biological fluid and Cr( VI ) in industrial waste water. The measured data were examined and compared with HPLC or HPTLCS. Test results show that the sensors and appa

  6. Multi-Phenotypic subtyping of circulating tumor cells using sequential fluorescent quenching and restaining

    Science.gov (United States)

    Adams, Daniel L.; Alpaugh, R. Katherine; Tsai, Susan; Tang, Cha-Mei; Stefansson, Steingrimur

    2016-09-01

    In tissue biopsies formalin fixed paraffin embedded cancer blocks are micro-sectioned producing multiple semi-identical specimens which are analyzed and subtyped proteomically, and genomically, with numerous biomarkers. In blood based biopsies (BBBs), blood is purified for circulating tumor cells (CTCs) and clinical utility is typically limited to cell enumeration, as only 2–3 positive fluorescent markers and 1 negative marker can be used. As such, increasing the number of subtyping biomarkers on each individual CTC could dramatically enhance the clinical utility of BBBs, allowing in depth interrogation of clinically relevant CTCs. We describe a simple and inexpensive method for quenching the specific fluors of fluorescently stained CTCs followed by sequential restaining with additional biomarkers. As proof of principle a CTC panel, immunosuppression panel and stem cell panel were used to sequentially subtype individual fluorescently stained patient CTCs, suggesting a simple and universal technique to analyze multiple clinically applicable immunomarkers from BBBs.

  7. Chlorophyll Fluorescence Emissions of Vegetation Canopies From High Resolution Field Reflectance Spectra

    Science.gov (United States)

    Middleton, E. M.; Corp, L. A.; Daughtry, C. S. T.; Campbell, P. K. Entcheva

    2006-01-01

    A two-year experiment was performed on corn (Zea mays L.) crops under nitrogen (N) fertilization regimes to examine the use of hyperspectral canopy reflectance information for estimating chlorophyll fluorescence (ChlF) and vegetation production. Fluorescence of foliage in the laboratory has proven more rigorous than reflectance for correlation to plant physiology. Especially useful are emissions produced from two stable red and far-red chlorophyll ChlF peaks centered at 685V10 nm and 735V5 nm. Methods have been developed elsewhere to extract steady state solar induced fluorescence (SF) from apparent reflectance of vegetation canopies/landscapes using the Fraunhofer Line Depth (FLD) principal. Our study utilized these methods in conjunction with field-acquired high spectral resolution canopy reflectance spectra obtained in 2004 and 2005 over corn crops, as part of an ongoing multi-year experiment at the USDA/Agriculture Research Service in Beltsville, MD. A spectroradiometer (ASD-FR Fieldspec Pro, Analytical Spectral Devices, Inc., Boulder, CO) was used to measure canopy radiances 1 m above plant canopies with a 22deg field of view and a 0deg nadir view zenith angle. Canopy and plant measurements were made at the R3 grain fill reproductive stage on 3-4 replicate N application plots provided seasonal inputs of 280, 140, 70, and 28 kg N/ha. Leaf level measurements were also made which included ChlF, photosynthesis, and leaf constituents (photosynthetic pigment, carbon (C), and N contents). Crop yields were determined at harvest. SIF intensities for ChlF were derived directly from canopy reflectance spectra in specific narrowband regions associated with atmospheric oxygen absorption features centered at 688 and 760 nm. The red/far-red S F ratio derived from these field reflectance spectra successfully discriminated foliar pigment levels (e.g., total chlorophyll, Chl) associated with N application rates in both corn crops. This canopy-level spectral ratio was also

  8. Temporal variability in chlorophyll fluorescence of back-reef corals in Ofu, American Samoa

    Science.gov (United States)

    Piniak, G.A.; Brown, E.K.

    2009-01-01

    Change in the yield of chlorophyll a fluorescence is a common indicator of thermal stress in corals. The present study reports temporal variability in quantum yield measurements for 10 coral species in Ofu, American Samoa - a place known to experience elevated and variable seawater temperatures. In winter, the zooxanthellae generally had higher dark-adapted maximum quantum yield (F v/Fm), higher light- adapted effective quantum yield (??F/F'm), and lower relative electron transport rates (rETR) than in the summer. Temporal changes appeared unrelated to the expected bleaching sensitivity of corals. All species surveyed, with the exception of Montipora grisea, demonstrated significant temporal changes in the three fluorescence parameters. Fluorescence responses were influenced by the microhabitat - temporal differences in fluorescence parameters were usually observed in the habitat with a more variable temperature regime (pool 300), while differences in Fv/Fm between species were observed only in the more environmentally stable habitat (pool 400). Such species-specific responses and microhabitat variability should be considered when attempting to determine whether observed in situ changes are normal seasonal changes or early signs of bleaching. ?? 2009 Marine Biological Laboratory.

  9. Binding of dicamba to soluble and bound extracellular polymeric substances (EPS) from aerobic activated sludge: a fluorescence quenching study.

    Science.gov (United States)

    Pan, Xiangliang; Liu, Jing; Zhang, Daoyong; Chen, Xi; Song, Wenjuan; Wu, Fengchang

    2010-05-15

    Binding of dicamba to soluble EPS (SEPS) and bound EPS (BEPS) from aerobic activated sludge was investigated using fluorescence spectroscopy. Two protein-like fluorescence peaks (peak A with Ex/Em=225 nm/342-344 nm and peak B with Ex/Em=275/340-344 nm) were identified in SEPS and BEPS. Humic-like fluorescence peak C (Ex/Em=270-275 nm/450-460 nm) was only found in BEPS. Fluorescence of the peaks A and B for SEPS and peak A for BEPS were markedly quenched by dicamba at all temperatures whereas fluorescence of peaks B and C for BEPS was quenched only at 298 K. A dynamic process dominated the fluorescence quenching of peak A of both SEPS and BEPS. Fluorescence quenching of peak B and C was governed a static process. The effective quenching constants (logK(a)) were 4.725-5.293 for protein-like fluorophores of SEPS and 4.23-5.190 for protein-like fluorophores of BEPS, respectively. LogK(a) for humic-like substances was 3.85. Generally, SEPS had greater binding capacity for dicamba than BEPS, and protein-like substances bound dicamba more strongly than humic-like substances. Binding of dicamba to SEPS and BEPS was spontaneous and exothermic. Electrostatic force and hydrophobic interaction forces play a crucial role in binding of dicamba to EPS.

  10. [Effects of plastic film mulching and rain harvesting modes on chlorophyll fluorescence characteristics, yield and water use efficiency of dryland maize].

    Science.gov (United States)

    Li, Shang-Zhong; Fan, Ting-Lu; Wang, Yong; Zhao, Gang; Wang, Lei; Tang, Xiao-Ming; Dang, Yi; Zhao, Hui

    2014-02-01

    The differences on chlorophyll fluorescence parameters, yield and water use efficiency of dryland maize were compared among full plastic film mulching on double ridges and planting in catchment furrows (FFDRF), half plastic film mulching on double ridges and planting in catchment furrows (HFDRF), plastic film mulching on ridge and planting in film-side (FS), and flat planting with no plastic film mulching (NM) under field conditions in dry highland of Loess Plateau in 2007-2012. The results showed that fluorescence yield (Fo), the maximum fluorescence yield (Fm), light-adapted fluorescence yield when PS II reaction centers were totally open (F), light-adapted fluorescence yield when PS II reaction centers closed (Fm'), the maximal photochemical efficiency of PS II (Fv/Fm), the actual photochemical efficiency of PS II in the light (Phi PS II), the relative electron transport rate (ETR), photochemical quenching (qP) and non-photochemical quenching (qN) in maize leaves of FFDRF were higher than that of control (NM), and the value of 1-qP was lower than that of control, at 13:00, chlorophyll fluorescence parameters values of FFDRF was significantly higher than control, which were increased by 5.3%, 56.8%, 10.7%, 36.3%, 23.6%, 56.7%, 64.4%, 45.5%, 23.6% and -55.6%, respectively, compared with the control. Yield and water use efficiency of FFDRF were the highest in every year no matter dry year, normal year, humid year and hail disaster year. Average yield and water use efficiency of FFDRF were 12,650 kg x hm(-2) and 40.4 kg x mm(-1) x hm(-2) during 2007-2012, increased by 57.8% and 61.6% compared with the control, respectively, and also significantly higher compared with HFDRF and PS. Therefore, it was concluded that FFDRF had significantly increased the efficiency of light energy conversion and improved the production capacity of dryland maize.

  11. Dynamic quenchers in fluorescently labeled membranes. Theory for quenching in a three-phase system.

    Science.gov (United States)

    Omann, G M; Glaser, M

    1985-05-01

    The theory for quenching of fluorescently labeled membranes by dynamic quenchers is described for a three-phase system: a fluorescently labeled membrane, a nonlabeled membrane, and an aqueous phase. Two different experimental protocols are possible to determine quenching parameters. Using the first protocol, partition coefficients and bimolecular quenching constants were determined for a hydrophobic quencher in carbazole-labeled membranes in the presence of an unlabeled reference membrane. These parameters determined for 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) using this three-phase analysis were in good agreement with values determined by a two-phase analysis without the reference lipid. Hence, the theory was verified. In the second protocol, the quencher partition coefficient was determined for unlabeled membranes in the presence of a carbazole-labeled reference membrane. Partition coefficients for DDE determined by this method were the same as partition coefficients determined for carbazole-labeled membranes using the two-phase analysis. The greater ease in determining partition coefficients and bimolecular quenching constants by the three-phase analysis and, in particular, the ability to determine the partition coefficient in unlabeled membranes make the three-phase analysis especially useful. This method was used to study the effect varying the membrane lipid composition has on the partition coefficient. The data indicate that partition coefficients of DDE in fluid membranes are not dramatically dependent upon polar head group composition, fatty acid composition, or cholesterol content. However, partitioning into gel-phase lipids is at least 100-fold less than fluid-phase lipids.

  12. Fluorescence quenching of coumarin 153 by hydroxyl-functionalized room temperature ionic liquids

    Science.gov (United States)

    Li, Shuang; Yu, Anchi; Lu, Rong

    2016-08-01

    Steady-state absorption and fluorescence as well as time-resolved fluorescence of coumarin 151 (C151) and coumarin 153 (C153) were measured in hydroxyl-functionalized ionic liquids ([HOEmim][BF4] and [HOEmim][N(CN)2]) and in nonhydroxyl-functionalized ionic liquids ([Emim][BF4] and [Emim][N(CN)2]). Both the steady-state fluorescence and time-resolved fluorescence observations reveal that hydroxyl-functionalized ionic liquid quenches the fluorescence of C153 while the nonhydroxyl-functionalized ionic liquid does not. We also measured the time-resolved fluorescence anisotropy of C151 and C153 in both [HOEmim][BF4] and [Emim][BF4]. It is found that the ratio of the rotational relaxation lifetime of C153 in [HOEmim][BF4] with respect to that in [Emim][BF4] is about 15% larger than that of C151 in [HOEmim][BF4] with respect to that in [Emim][BF4], indicating extra interaction between C153 and [HOEmim][BF4] exists except the effect of the viscosity of ionic liquid.

  13. Determination of protease subsite preference on SPOT peptide array by fluorescence quenching-based assay.

    Science.gov (United States)

    Kim, Do-Hyun; Shin, Dong-Sik; Lee, Yoon-Sik

    2012-06-01

    A peptide SPOT array was synthesized on a glass chip and used to determine protease subsite preference. To synthesize a peptide array for positional scanning, the ratio of the isokinetic concentration was determined for every Fmoc-amino acid except Cys. Based on this ratio, a peptide array consisting of Dabcyl-X-X-P(2)-Arg-X-X-X-Lys(FITC) (X: equimolar mixture of 19 amino acids, P(2): one of 19 amino acids) was synthesized on a chitosan-grafted glass chip. Subsequently, the peptide substrates on the array were hydrolyzed by thrombin to screen for subsite specificity using a fluorescence quenching-based assay. The P(2) subsite specificity of thrombin was screened by the fluorescence images obtained after hydrolysis. Pro at the P(2) subsite showed the highest specificity for thrombin based on both the fluorescence quenching-based assay and the solution phase assay. From these results, we confirmed that our mixture-based peptide SPOT array format on the chitosan-grafted glass chips could be used to determine protease subsite preference.

  14. Enhanced fluorescence quenching in an acridine orange - alizarin red system through matrine and its analytical application

    Science.gov (United States)

    Wei, Xiaoling; Wang, Xiaojun; Gong, Qi; Wang, Lisheng; Zhou, Shiwu

    2015-01-01

    This study shows that alizarin red (AR) only slightly quenched fluorescence for acridine orange (AO) in an AR/AO mixed solution at pH = 5-6. The reduced fluorescent signal was closely and linearly associated with the level of MT added to the system, which is the basis for a new quantitative MT assay method using the fluorescence quenching reaction in the AO-AR system. The results show that under optimal conditions, this method had a 14.9-43.5 mg L-1 linear detection range with a 1.38 mg L-1 detection limit and 1.24% precision. In addition, this method was used to determine the MT levels in the commercially available MT-containing pesticides and suppositories, which showed a 96.6-103% recovery. Therefore, this method has multiple advantages, including simple and fast operation, high accuracy and low cost. Moreover, herein, we investigated the underlying mechanism in-depth using an ultraviolet (UV) spectroscopic technique.

  15. Fluorescence quenching study on the interaction of ferroferric oxide nanoparticles with bovine serum albumin

    Science.gov (United States)

    Hao, Changchun; Xu, Guangkuan; Feng, Ying; Lu, Linhao; Sun, Wenyuan; Sun, Runguang

    2017-09-01

    Fluorescence quenching was used to study the potential interaction mechanism of Bovine serum albumin (BSA) with either hydrophilic ferroferric oxide (Fe3O4) nanoparticles (NPs) or hydrophobic Fe3O4 NPs. The experimental results indicated the mechanism between BSA and hydrophilic Fe3O4 NPs was static quenching and the one between BSA and hydrophobic Fe3O4 NPs was dynamic process that was drove by Förster's resonance energy transfer (FRET). And the binding parameters for the interaction of BSA with either hydrophilic or hydrophobic Fe3O4 NPs were calculated by using the fluorescence quenching measurement. The binding constant (KA) values of hydrophilic Fe3O4 NPs were 8518.73 ± 23.35 (at 298 K), 1190.31 ± 15.41 (at 306 K) and 321.97 ± 8.57 (at 313 K), respectively. The thermodynamic analysis implied that the intermolecular forces between BSA and hydrophilic Fe3O4 NPs were Van der Waals interaction or hydrogen bond, because the values of ΔH and ΔS between them were negative. While the one of BSA and hydrophobic Fe3O4 NPs involved hydrophobic forces, owing to the positive ΔH and ΔS between them. But they were all enthalpy-driven and exothermic, since their ΔG values were all negative. Synchronous fluorescence spectroscopy suggested that the conformation of tryptophan residue of BSA was changed in the presence of hydrophilic Fe3O4 NPs or hydrophobic Fe3O4 NPs, because the position of the maximum emission wavelength had a discernible red shift.

  16. Rapid fluorometric determination of perfluorooctanoic acid by its quenching effect on the fluorescence of quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qi; Huang, Aizhen; Wang, Nan, E-mail: nwang@hust.edu.cn; Zheng, Guan; Zhu, Lihua

    2015-05-15

    Analysis of perfluorooctanoic acid (PFOA) usually requires a combination of high-performance liquid chromatography and mass spectrometry, which is expensive and time-consuming. In the present work, water-soluble CdS quantum dots (QDs) were employed to develop a simple and rapid fluorometric method for the determination of PFOA. Strongly fluorescent CdS QDs were prepared by using 3-mercaptopropionic acid (MPA) as a stabilizer. It was observed that PFOA strongly quenched the fluorescence emission of the MPA-CdS QDs because PFOA promotes the aggregation of MPA-CdS QDs through a fluorine–fluorine affinity interaction. Under optimum conditions, the fluorescence intensity of MPA-CdS QDs was observed to decrease linearly with an increase in the concentration of PFOA from 0.5 to 40 μmol L{sup −1}, with a limit of detection of 0.3 μmol L{sup −1}. This new method was successfully implemented for the analysis of PFOA-spiked textile samples, with recoveries ranging from 95% to 113%. - Highlights: • PFOA significantly quenched the fluorescence emission of quantum dots (QDs). • A rapid and simple fluorescence sensor was proposed for determining PFOA by QDs. • PFOA determination could be completed within approximately 10 min. • The developed method had a working range of 0.5 to 40 μmol L{sup −1} and a detection limit of 0.3 μmol L{sup −1}.

  17. Use of in vivo chlorophyll fluorescence to estimate photosynthetic activity and biomass productivity in microalgae grown in different culture systems

    Directory of Open Access Journals (Sweden)

    Félix L Figueroa

    2013-11-01

    Full Text Available In vivo chlorophyll fluorescence associated to Photosystem II is being used to evaluate photosynthetic activity of microalgae grown in different types of photobioreactors; however, controversy on methodology is usual. Several recommendations on the use of chlorophyll fluorescence to estimate electron transport rate and productivity of microalgae grown in thin-layer cascade cultivators and methacrylate cylindrical vessels are included. Different methodologies related to the measure of photosynthetic activity in microalgae are discussed: (1 measurement of light absorption, (2 determination of electron transport rates versus irradiance and (3 use of simplified devices based on pulse amplitude modulated (PAM fluorescence as Junior PAM or Pocket PAM with optical fiber and optical head as measuring units, respectively. Data comparisons of in vivo chlorophyll fluorescence by using these devices and other PAM fluorometers as Water-PAM in the microalga Chlorella sp. (Chlorophyta are presented. Estimations of carbon production and productivity by transforming electron transport rate to gross photosynthetic rate (as oxygen evolution using reported oxygen produced per photons absorbed values and carbon photosynthetic yield based on reported oxygen/carbon ratio are also shown. The limitation of ETR as estimator of photosynthetic and biomass productivity is discussed. Low cost:quality PAMs can promote monitoring of chlorophyll fluorescence in algal biotechnology to estimate the photosynthetic activity and biomass productivity.

  18. [Flag leaf photosynthetic characteristics, change in chlorophyll fluorescence parameters, and their relationships with yield of winter wheat sowed in spring].

    Science.gov (United States)

    Xu, Lan; Gao, Zhi-qang; An, Wei; Li, Yan-liang; Jiao, Xiong-fei; Wang, Chuang-yun

    2016-01-01

    With five good winter wheat cultivars selected from the middle and lower reaches of Yangtze River and Southwest China as test materials, a field experiment in Xinding basin area of Shanxi Province was conducted to study the photosynthetic characteristics, chlorophyll content, and chlorophyll fluorescence parameters of flag leaf at different sowing dates, as well as the correlations between these indices and yield for two years (2013-2014). The results showed that the difference in most fluorescence parameters except chlorophyll content among cultivars was significant. The correlations between these fluorescence parameters and yield were significant. The variation coefficient of chlorophyll (Chl) content was low (0.12-0.17), and that of performance index based on absorption (PIabs) was high (0.32-0.39), with the partial correlation coefficients of them with grain yield from 2013 to 2014 ranged in 0.70-0.81. Under the early sowing condition, the grain yield positively correlated with PIabs at flowering and filling stages and chlorophyll content at grain filling stage, but negatively correlated with the relative variable fluorescence at I point (Vi) at grain filling stage. About 81.1%-82.8% of grain yield were determined by the variations of PIabs, Chl, and Vi. Wheat cultivars had various performances in the treatments with different sowing dates and a consistent trend was observed in the two experimental years. Among these 5 cultivars, Yangmai 13 was suitable for early sowing, with the flag leaf photosynthetic rate (Pn), Chl, most fluorescence parame-ters, and grain yield showed obviously high levels. In conclusion, under early sowing condition chlorophyll content at grain filling stages, PIabs at flowering and filling stages, and Pn were important indices for selecting wheat cultivars with high photosynthetic efficiency.

  19. Modelling satellite-level solar-induced chlorophyll fluorescence and its comparison with OCO-2 observations

    Science.gov (United States)

    Pradhan, Rohit; Gohel, Ankit

    2016-04-01

    Solar Induced chlorophyll Fluorescence (SIF) is a direct measure of photosynthesis rate as it is emitted by the photosynthetic system. This paper reports a method to model SIF over India by assimilating spatial inputs (LAI, Chlorophyll content etc.) into FluorMOD leaf and canopy model. Modelled SIF was then compared to Orbiting Carbon Observatory (OCO-2) SIF observations from September 2014 to August 2015. Modelled SIF at 757 nm averaged over the country varied between 0.18 to 0.33 W m-2 sr-1 μm-1 whereas SIF at 771 nm varied between 0.10 to 0.19 W m-2 sr-1 μm-1. OCO-2 observed SIF at 757 nm averaged over the country ranged from 0.18 to 0.42 Wm-2sr-1μm-1. Fairly good agreement (r=0.77, p<0.01 at 757nm; r=0.71, p<0.05 at 771 nm) was observed between modelled and observed SIF except for summer months of April and May. This paper presents a new approach to upscale a leaf and canopy level model to estimate SIF over entire country.

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

    Science.gov (United States)

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

    2013-11-01

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

  1. Tundra photosynthesis captured by satellite-observed solar-induced chlorophyll fluorescence

    Science.gov (United States)

    Luus, K. A.; Commane, R.; Parazoo, N. C.; Benmergui, J.; Euskirchen, E. S.; Frankenberg, C.; Joiner, J.; Lindaas, J.; Miller, C. E.; Oechel, W. C.; Zona, D.; Wofsy, S.; Lin, J. C.

    2017-02-01

    Accurately quantifying the timing and magnitude of respiration and photosynthesis by high-latitude ecosystems is important for understanding how a warming climate influences global carbon cycling. Data-driven estimates of photosynthesis across Arctic regions often rely on satellite-derived enhanced vegetation index (EVI); we find that satellite observations of solar-induced chlorophyll fluorescence (SIF) provide a more direct proxy for photosynthesis. We model Alaskan tundra CO2 cycling (2012-2014) according to temperature and shortwave radiation and alternately input EVI or SIF to prescribe the annual seasonal cycle of photosynthesis. We find that EVI-based seasonality indicates spring "green-up" to occur 9 days prior to SIF-based estimates, and that SIF-based estimates agree with aircraft and tower measurements of CO2. Adopting SIF, instead of EVI, for modeling the seasonal cycle of tundra photosynthesis can result in more accurate estimates of growing season duration and net carbon uptake by arctic vegetation.

  2. Effects of ozone fumigation on epiphytic macrolichens: ultrastructure, CO2 gas exchange and chlorophyll fluorescence.

    Science.gov (United States)

    Scheidegger, C; Schroeter, B

    1995-01-01

    The lichen species Anaptychia ciliaris, Collema nigrescens, Evernia prunastri, Hypogymnia bitteri, Lobaria pulmonaria, Pseudevernia furfuracea and Usnea rigida s.l. were fumigated with site-relevant concentrations (for Central Europe) of ozone over 80 days (180 microg m(-3) during daytime, 80 microg m(-3) during the night). Chlorophyll fluorescence measurements revealed a significant reduction of Fv/Fm after ozone fumigation in five of the species investigated, indicating severe stress on photosystem II due to ozone. The physiological impairment paralleled our fine structural investigations, revealing a significantly higher percentage of collapsed photobiont cells. This indicates that the effects of ambient ozone concentrations under experimental conditions included biophysical and physiological, as well as structural impairment in the lichens studied.

  3. Linking chlorophyll a fluorescence to photosynthesis for remote sensing applications: mechanisms and challenges.

    Science.gov (United States)

    Porcar-Castell, Albert; Tyystjärvi, Esa; Atherton, Jon; van der Tol, Christiaan; Flexas, Jaume; Pfündel, Erhard E; Moreno, Jose; Frankenberg, Christian; Berry, Joseph A

    2014-08-01

    Chlorophyll a fluorescence (ChlF) has been used for decades to study the organization, functioning, and physiology of photosynthesis at the leaf and subcellular levels. ChlF is now measurable from remote sensing platforms. This provides a new optical means to track photosynthesis and gross primary productivity of terrestrial ecosystems. Importantly, the spatiotemporal and methodological context of the new applications is dramatically different compared with most of the available ChlF literature, which raises a number of important considerations. Although we have a good mechanistic understanding of the processes that control the ChlF signal over the short term, the seasonal link between ChlF and photosynthesis remains obscure. Additionally, while the current understanding of in vivo ChlF is based on pulse amplitude-modulated (PAM) measurements, remote sensing applications are based on the measurement of the passive solar-induced chlorophyll fluorescence (SIF), which entails important differences and new challenges that remain to be solved. In this review we introduce and revisit the physical, physiological, and methodological factors that control the leaf-level ChlF signal in the context of the new remote sensing applications. Specifically, we present the basis of photosynthetic acclimation and its optical signals, we introduce the physical and physiological basis of ChlF from the molecular to the leaf level and beyond, and we introduce and compare PAM and SIF methodology. Finally, we evaluate and identify the challenges that still remain to be answered in order to consolidate our mechanistic understanding of the remotely sensed SIF signal.

  4. Impact of elevated temperatures on specific leaf weight, stomatal density, photosynthesis and chlorophyll fluorescence in soybean.

    Science.gov (United States)

    Jumrani, Kanchan; Bhatia, Virender Singh; Pandey, Govind Prakash

    2017-03-01

    High-temperature stress is a major environmental stress and there are limited studies elucidating its impact on soybean (Glycine max L. Merril.). The objectives of present study were to quantify the effect of high temperature on changes in leaf thickness, number of stomata on adaxial and abaxial leaf surfaces, gas exchange, chlorophyll fluorescence parameters and seed yield in soybean. Twelve soybean genotypes were grown at day/night temperatures of 30/22, 34/24, 38/26 and 42/28 °C with an average temperature of 26, 29, 32 and 35 °C, respectively, under greenhouse conditions. One set was also grown under ambient temperature conditions where crop season average maximum, minimum and mean temperatures were 28.0, 22.4 and 25.2 °C, respectively. Significant negative effect of temperature was observed on specific leaf weight (SLW) and leaf thickness. Rate of photosynthesis, stomatal conductance and water use efficiency declined as the growing temperatures increased; whereas, intercellular CO2 and transpiration rate were increased. With the increase in temperature chlorophyll fluorescence parameters such as Fv/Fm, qP and PhiPSII declined while there was increase in qN. Number of stomata on both abaxial and adaxial surface of leaf increased significantly with increase in temperatures. The rate of photosynthesis, PhiPSII, qP and SPAD values were positively associated with leaf thickness and SLW. This indicated that reduction in photosynthesis and associated parameters appears to be due to structural changes observed at higher temperatures. The average seed yield was maximum (13.2 g/pl) in plants grown under ambient temperature condition and declined by 8, 14, 51 and 65% as the temperature was increased to 30/22, 34/24, 38/26 and 42/28 °C, respectively.

  5. Prospects for Chlorophyll Fluorescence Remote Sensing from the Orbiting Carbon Observatory-2

    Science.gov (United States)

    Frankenberg, Christian; Odell, Chris; Berry, Joseph; Guanter, Luis; Joiner, Joanna; Kohler, Philipp; Pollock, Randy; Taylor, Thomas E.

    2014-01-01

    The Orbiting Carbon Observatory-2 (OCO-2), scheduled to launch in July 2014, is a NASA mission designed to measure atmospheric CO2. Its main purpose is to allow inversions of net flux estimates of CO2 on regional to continental scales using the total column CO2 retrieved using high-resolution spectra in the 0.76, 1.6, and 2.0 nm ranges. Recently, it was shown that solar-induced chlorophyll fluorescence (SIF), a proxy for gross primary production (GPP, carbon uptake through photosynthesis), can be accurately retrieved from space using high spectral resolution radiances in the 750 nm range from the Japanese GOSAT and European GOME-2 instruments. Here, we use real OCO-2 thermal vacuum test data as well as a full repeat cycle (16 days) of simulated OCO-2 spectra under realistic conditions to evaluate the potential of OCO-2 for retrievals of chlorophyll fluorescence and also its dependence on clouds and aerosols. We find that the single-measurement precision is 0.3-0.5 Wm(exp -2)sr(exp -1) nm(exp -1) (15-25% of typical peak values), better than current measurements from space but still difficult to interpret on a single-sounding basis. The most significant advancement will come from smaller ground-pixel sizes and increased measurement frequency, with a 100-fold increase compared to GOSAT (and about 8 times higher than GOME-2). This will largely decrease the need for coarse spatial and temporal averaging in data analysis and pave the way to accurate local studies.We also find that the lack of full global mapping from the OCO-2 only incurs small representativeness errors on regional averages. Eventually, the combination of net ecosystem exchange (NEE) derived from CO2 source/sink inversions and SIF as proxy for GPP from the same satellite will provide a more process-based understanding of the global carbon cycle.

  6. Leaf Chlorophyll Fluorescence and Gas Exchange Response to Different Light Levels in Platycerium bifurcatum

    Directory of Open Access Journals (Sweden)

    Ruzana-Adibah M. Sanusi

    2011-01-01

    Full Text Available Problem statement: Platycerium bifurcatum (Cav. C. Chr. is epiphytes which lives in forest canopy and commonly used for its ornamental value. In these environments, they were always exposed to many types of stresses such as high light intensity. Light intensity plays an important role in affecting plants physiological performance. Therefore, the purpose of this study was to investigate physiological responses of P. bifurcatum to light stress. Approach: In this study, P. bifurcatum were grown under four different Photosynthetic Active Radiation (PAR levels which were 20 µmol m-2 s-1 (T1, 70 µmol m-2 s-1 (T2, 200 µmol m-2 s-1 (T3 and 1500 µmol m-2 s-1 (T4. Leaf gas exchange and chlorophyll fluorescence were used to evaluate the stress response of various levels of light intensity. All measurements were carried out on weekly basis for twelve weeks. Results: Results showed that Anet value of T1, T2 and T3 in the range near to the average Anet value for most epiphytes. Conversely, T4 showed lower value in Anet with 1.797 µmol CO2 m-2 s-1. Fv/Fm ratio in T3 and T4 were below 0.8 indicates that there was a sign of stress occurred in these treatments. However Anet of T3 was not affected although there have been event of photoinhibition observed in the treatment. On the contrary, T4 was fully affected by high light intensity as there was a reduction of Fv/Fm ratio and also Anet. T1 and T2 of Anet and Fv/Fm ratio values ranged of unstressed plants after subjected to light treatment. Conclusion: Measurement of leaf chlorophyll fluorescence and gas exchange are useful to detection of light stress in P. bifurcatum. Different levels of light intensity were significantly affecting physiological attributes of P. bifurcatum.

  7. An investigation on fluorescence quenching of certain porphyrins by colloidal CdS

    Energy Technology Data Exchange (ETDEWEB)

    Asha Jhonsi, M.; Kathiravan, A. [School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Renganathan, R., E-mail: rrengas@yahoo.co [School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)

    2009-08-15

    Certain porphyrin derivatives namely meso-tetraphenylporphyrin (TPP), meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP), meso-tetrakis(4-sulfonatophenyl)porphyrin (TSPP) were examined as sensitizers for colloidal CdS. The interaction of these porphyrins and colloidal CdS were studied by absorption, infrared, steady state and time resolved fluorescence spectroscopy and transient absorption techniques. The apparent association constants (K{sub app}) resulting from adsorption of porphyrins on CdS surface were calculated from both absorption and fluorescence studies and they agree well. Using all the spectroscopic measurements we confirmed that the interaction between porphyrins and colloidal CdS occurs through ground state complex formation and the quenching follows static mechanism.

  8. Laser-induced chlorophyll fluorescence: a technique for detection of dimethoate effect on chlorophyll content and photosynthetic activity of wheat plant.

    Science.gov (United States)

    Pandey, Jitendra Kumar; Gopal, R

    2011-03-01

    Laser-induced chlorophyll fluorescence (LICF) spectra and fluorescence induction kinetics (FIK) curves of wheat plant leaves treated with different concentrations (50, 100 and 200 ppm) of dimethoate are recorded. LICF spectra are recorded in the region of 650-780 nm using violet diode laser (405 nm) and FIK curve at 685 and 730 nm with red diode laser (635 nm) for excitation. The fluorescence intensity ratios (FIR) are determined from LICF spectra and vitality index (R(fd)) from FIK curves. These parameters along with photosynthetic pigment contents and growth parameters are used to analyze the effect of dimethoate on wheat plants. The result indicates that lower concentration of 50 ppm shows stimulatory response while higher concentrations of dimethoate are hazardous for growth, photosynthetic pigments and activity of wheat plants.

  9. Temperature and light tolerance of representative brown,green and red algae in tumble culture revealed by chlorophyll fluorescence measurements

    Institute of Scientific and Technical Information of China (English)

    PANG Shaojun; SHAN Tifeng

    2008-01-01

    Laminaria japonica,Undaria pinnatifida,Ulva lactuca,Grateloupia turuturu and Palmaria palmata are suitable species that fit the requirements of a seaweed-animal integrated aquaculture system in terms of their viable biomass,rapid growth and promising nutrient uptake rates. In this investigation,the responses of the optimal chlorophyll fluolescence yield of the five algal species in tumble culture were assessed at a temperature range of 10~30℃.The results revealed that Ulva lactuca was the most resistant species to high temperature,withstanding 30℃ for 4 h without apparent decline in the optimal chlorophyll fluorescence yield. While the arctic alga Palmaria palmata was the most vulnerable one,showing significant decline in the optimal chlorophyll fluorescence yield at 25℃ for 2 h.The cold-water species Laminaria japonica,however,demonstrated strong ability to cope with higher temperature(24~26℃)for shorter time(within 24 h)without significant decline in the optimal chlorophyll fluorescence yield.Grateloupia turuturu showed a general decrease in the optimal chiorophyll fluores-cence yield with the rising temperature from 23 to 30℃,similar to the temperate kelp Undaria pinnatifida.Changes of chio-rophyll fluorescence yields of these algae were characterized differently indicating the existence of species-unique strategy to cope with high light.Measurements of the optimal chlorophyll fluorescence yield after short exposure to direct solar irradiance revealed how long these exposures could be without significant photoinhibition or with promising recovery in photosynthetic activities. Seasonal pattern of alternation of algal species in tank culture in the Northern Hemisphere at the latitude of 36°Nwas proposed according to these basic measurements.

  10. [Effects of simulating acid rain on photosynthesis and chlorophyll fluorescence parameters of Quercus glauca Quercus glauca].

    Science.gov (United States)

    Wang, Sai; Yi, Li-Ta; Yu, Shu-Quan; Zhang, Chao; Shi, Jing-Jing

    2014-08-01

    At three levels of simulated acid rainfall intensities with pH values of 2.5 (severe), 40 (medium) and 5.6 (light) respectively, the responses of chlorophyll fluorescence and photosynthetic parameters of Quercus glauca seedlings were studied in three acid rainfall treatments, i. e. only the aboveground of seedlings exposed to acid rain (T1), both of the seedlings and soil exposed to acid rain (T2), only the soil exposed to acid rain (T3) compared with blank control (CK). Under the severe acid rainfall, T1 significantly inhibited chlorophyll synthesis, and thus reduced the primary photochemical efficiency of PS II ( F(v)/F(m)), potential activity of PS II (F(v)/F(o)) , apparent quantum (Y), net photosynthetic rate (P(n)), and transpiration rate (T(r)), but increased the light compensation point (LCP) and dark respiration rate (R(d)) of Q. glauca seedlings. T2 inhibited, but T3 played a little enhancement on the aforementioned parameters of Q. glauca seedlings. Under the conditions of medium and light acid rainfall intensities, the above parameters in the three treatments were higher than that of CK, except with lower R(d). The chlorophyll fluorescence and photosynthetic parameters showed a similar tendency in the three treatments, i. e. T2>T3 >T1. It indicated that T1 had the strongest inhibition on seedlings in condition of the severe acid rainfall, while T2 had the most dramatic facilitating effect on seedlings under the medium and light acid rainfall. Intensity of acid rainfall had significant influences on SPAD, F(v)/F(m), F(v)/F(o), Y, P(n), T(r), and maximum photosynthetic rate (A(max)), whereas treatments of acid rainfall affected SPAD, F(v)/F(m), Y, P(n), T(r), A(max) and light saturation point (LSP). The interaction of acid rainfall intensities and treatments played significant effects on SPAD, F(v)/F(m), Y, P(n) and A(max).

  11. Time-resolved fluorescence quenching studies of sodium lauryl ether sulfate micelles

    Energy Technology Data Exchange (ETDEWEB)

    Friedrich, Leidi C.; Silva, Volnir O.; Quina, Frank H., E-mail: quina@usp.br [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto de Quimica; Moreira Junior, Paulo F. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Escola Politecnica. Departamento de Engenharia Quimica; Tcacenco, Celize M. [Fundacao Instituto de Ensino para Osasco (FIEO/UNIFIEO), SP (Brazil). Centro Universitario FIEO. Centro de Estudos Quimicos

    2013-02-15

    Aggregation numbers (N{sub Ag}) of micelles of the commercial anionic detergent sodium lauryl ether sulfate (SLES), with an average of two ethylene oxide subunits, were determined at 30 and 40 deg C by the time-resolved fluorescence quenching method with pyrene as the fluorescent probe and the N-hexadecylpyridinium ion as the quencher. The added-salt dependent growth of SLES micelles ({gamma} = 0.11-0.15, where {gamma} is the slope of a plot of log aggregation number vs. log [Y{sub aq}] and [Y{sub aq}] is the sodium counterion concentration free in the intermicellar aqueous phase) is found to be significantly lower than that of sodium alkyl sulfate micelles ({gamma} ca. 0.25), a difference attributed to the larger headgroup size of SLES. The I{sub 1}/I{sub 3} vibronic intensity ratio and the rate constant for intramicellar quenching of pyrene show that the pyrene solubilization microenvironment and the intramicellar microviscosity are insensitive to micelle size or the presence of added salt. (author)

  12. Fluorescent proteins as biosensors by quenching resonance energy transfer from endogenous tryptophan: detection of nitroaromatic explosives.

    Science.gov (United States)

    Gingras, Alexa; Sarette, Joseph; Shawler, Evan; Lee, Taeyoung; Freund, Steve; Holwitt, Eric; Hicks, Barry W

    2013-10-15

    Ensuring domestic safety from terrorist attack is a daunting challenge because of the wide array of chemical agents that must be screened. A panel of purified fluorescent protein isoforms (FPs) was screened for the ability to detect various explosives, explosive simulants, and toxic agents. In addition to their commonly used visible excitation wavelengths, essentially all FPs can be excited by UV light at 280 nm. Ultraviolet illumination excites electrons in endogenous tryptophan (W) residues, which then relax by Förster Resonance Energy Transfer (FRET) to the chromophore of the FP, and thus the FPs emit with their typical visible spectra. Taking advantage of the fact that tryptophan excitation can be quenched by numerous agents, including nitroaromatics like TNT and nitramines like RDX, it is demonstrated that quenching of visible fluorescence from UV illumination of FPs can be used as the basis for detecting these explosives and explosive degradation products. This work provides the foundation for production of an array of genetically-modified FPs for in vitro biosensors capable of rapid, simultaneous, sensitive and selective detection of a wide range of explosive or toxic agents. Published by Elsevier B.V.

  13. Time-resolved fluorescence quenching studies of sodium lauryl ether sulfate micelles

    Energy Technology Data Exchange (ETDEWEB)

    Friedrich, Leidi C.; Silva, Volnir O.; Quina, Frank H., E-mail: quina@usp.br [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto de Quimica; Moreira Junior, Paulo F. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Escola Politecnica. Departamento de Engenharia Quimica; Tcacenco, Celize M. [Fundacao Instituto de Ensino para Osasco (FIEO/UNIFIEO), SP (Brazil). Centro Universitario FIEO. Centro de Estudos Quimicos

    2013-02-15

    Aggregation numbers (N{sub Ag}) of micelles of the commercial anionic detergent sodium lauryl ether sulfate (SLES), with an average of two ethylene oxide subunits, were determined at 30 and 40 deg C by the time-resolved fluorescence quenching method with pyrene as the fluorescent probe and the N-hexadecylpyridinium ion as the quencher. The added-salt dependent growth of SLES micelles ({gamma} = 0.11-0.15, where {gamma} is the slope of a plot of log aggregation number vs. log [Y{sub aq}] and [Y{sub aq}] is the sodium counterion concentration free in the intermicellar aqueous phase) is found to be significantly lower than that of sodium alkyl sulfate micelles ({gamma} ca. 0.25), a difference attributed to the larger headgroup size of SLES. The I{sub 1}/I{sub 3} vibronic intensity ratio and the rate constant for intramicellar quenching of pyrene show that the pyrene solubilization microenvironment and the intramicellar microviscosity are insensitive to micelle size or the presence of added salt. (author)

  14. Fluorescence quenching study of quercetin interaction with bovine milk xanthine oxidase

    Science.gov (United States)

    Rasoulzadeh, Farzaneh; Jabary, Hamideh Nadjarpour; Naseri, Abdolhossein; Rashidi, Mohammad-Reza

    2009-02-01

    Quercetin is a natural flavonoid with many important therapeutic properties. The interaction of this polyphenolic compound bovine milk xanthine oxidase as one of its major target proteins was studied using fluorescence quenching method for the first time. It was found that the fluorescence quenching of xanthine oxidase occurs through a static mechanism. The results revealed the presence of a single binding site on xanthine oxidase with the binding constant value equals to 1.153 × 10 4 l mol -1 at 310 K and pH 7.4. The thermodynamic parameters were also calculated at different temperatures. The enthalpy and entropy changes were found as -10.661 kJ mol -1 and +43.321 J mol -1 K -1 indicating that both hydrogen binding and hydrophobic are involved in the interaction of this polyphenolic natural compound with xanthine oxidase. The results may provide a ground for further studies with different flavonoids to find a safe alternative for allopurinol, the only xanthine oxidase inhibitor with clinical application.

  15. MagiProbe: a novel fluorescence quenching-based oligonucleotide probe carrying a fluorophore and an intercalator

    OpenAIRE

    Yamane, Akio

    2002-01-01

    Fluorescence is the favored signaling technology for molecular diagnoses. Fluorescence energy transfer-based methods are powerful homogeneous assay tools. A novel oligonucleotide probe, named MagiProbe, which is simple to use, is described, and information given about the duplex formed with a target. The probe internally has a fluorophore and an intercalator. Its fluorescence is quenched by the intercalator in the absence of a target sequence. On hybridization with a target sequence, the prob...

  16. Chlorophyll a fluorescence induction (Kautsky curve) in a Venus flytrap (Dionaea muscipula) leaf after mechanical trigger hair irritation.

    NARCIS (Netherlands)

    Vredenberg, W.J.; Pavlovic, A.

    2013-01-01

    This paper describes experiments on transient changes in chlorophyll a fluorescence in traps of the carnivorous plant Venus flytrap (Dionaea muscipula) that occur in association with mechanical stimulation of trigger hairs and propagation of action potentials (APs). The experiments show the

  17. Method 445.0 In Vitro Determination of Chlorophyll a and Pheophytin ain Marine and Freshwater Algae by Fluorescence

    Science.gov (United States)

    This method provides a procedure for low level determination of chlorophyll a (chl a) and its magnesium free derivative, pheophytin a (pheo a), in marine and freshwater phytoplankton using fluorescence detection.(1,2) Phaeophorbides present in the sample are determined collective...

  18. Method 445.0 In Vitro Determination of Chlorophyll a and Pheophytin ain Marine and Freshwater Algae by Fluorescence

    Science.gov (United States)

    This method provides a procedure for low level determination of chlorophyll a (chl a) and its magnesium free derivative, pheophytin a (pheo a), in marine and freshwater phytoplankton using fluorescence detection.(1,2) Phaeophorbides present in the sample are determined collective...

  19. Chlorophyll Fluorescence Sorting Method to Improve Quality of Capsicum Pepper Seed Lots Produced from Different Maturity Fruits

    NARCIS (Netherlands)

    Kenanoglu, B.B.; Demir, I.; Jalink, H.

    2013-01-01

    This work was conducted to investigate the efficacy of chlorophyll fluorescence (CF) sorting to improve seed germination, seedling emergence, and vigor of seeds produced from different maturity fruits of four different cultivars. Four harvest dates from each cultivar were evaluated by harvesting ora

  20. Chlorophyll Fluorescence Sorting Method to Improve Quality of Capsicum Pepper Seed Lots Produced from Different Maturity Fruits

    NARCIS (Netherlands)

    Kenanoglu, B.B.; Demir, I.; Jalink, H.

    2013-01-01

    This work was conducted to investigate the efficacy of chlorophyll fluorescence (CF) sorting to improve seed germination, seedling emergence, and vigor of seeds produced from different maturity fruits of four different cultivars. Four harvest dates from each cultivar were evaluated by harvesting ora

  1. The Impact of Different Water Regime on Chlorophyll Fluorescence of Pyrus pyraster L. and Sorbus domestica L

    Directory of Open Access Journals (Sweden)

    Viera Šajbidorová

    2015-01-01

    Full Text Available The water deficit is considered to be significant cause of photosynthesis defects. Measuring of chlorophyll fluorescence is one of the methods revealing defects in the photosynthetic apparatus. The experiment was established with two woody plant (Pyrus pyraster L. and Sorbus domestica L. cultivated in two different regimes of the substrate saturation. The measurement of the modulated fluorescence of chlorophyll a was done by FMS1 fluorometer during three-week period between June and September (2012 and 2013. There were analysed selected parameters of chlorophyll fluorescence: Fv/Fm – maximum quantum efficiency of PSII, ΦPSII – effective quantum yield of PSII and RFD – chlorophyll fluorescence decrease ratio. According to the obtained results, Pyrus pyraster has probably higher potential for adaptation to water deficiency. There were recorded the significant decreases mainly in the values of parameter RFD and ΦPSII for Sorbus domestica within duration of experiment with different water regime in both growing seasons 2012 and 2013. The results document a weak sensitivity of the parameter Fv/Fm on changes in the amount of available water in the substrate in both taxa.

  2. Using violet laser-induced chlorophyll fluorescence emission spectra for crop yield assessment of cowpea (Vigna unguiculata (L) Walp) varieties

    Science.gov (United States)

    Anderson, Benjamin; Buah-Bassuah, Paul K.; Tetteh, Jonathan P.

    2004-07-01

    The use of violet laser-induced chlorophyll fluorescence (LICF) emission spectra to monitor the growth of five varieties of cowpea in the University of Cape Coast Botanical Garden is presented. Radiation from a continuous-wave violet laser diode emitting at 396 nm through a fibre is closely incident on in vivo leaves of cowpea to excite chlorophyll fluorescence, which is detected by an integrated spectrometer with CCD readout. The chlorophyll fluorescence spectra with peaks at 683 and 731 nm were used for growth monitoring of the cowpea plants over three weeks and analysed using Gaussian spectral functions with curve fitted parameters to determine the peak positions, area under the spectral curve and the intensity ratio F683/F731. The variation in the intensity ratio of the chlorophyll bands showed sensitive changes indicating the photosynthetic activity of the cowpea varieties. A discussion of the fluorescence result as compared to conventional assessment is presented with regard to discrimination between the cowpea varieties in terms of crop yield performance.

  3. Gas exchange and chlorophyll fluorescence of pea (Pisum sativum L.) plants in response to ambient ozone at a rural site in Egypt

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, I.M.; Basahi, J.M. [Air Pollution Laboratory (APL), Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, P. O. Box 80216, Jeddah 21589 (Saudi Arabia); Hassan, I.A., E-mail: ihassan_eg@yahoo.com [Air Pollution Laboratory (APL), Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, P. O. Box 80216, Jeddah 21589 (Saudi Arabia); Department of Botany, Faculty of Science, Alexandria University, 21526 El Shatby, Alexandria (Egypt)

    2014-11-01

    Egyptian pea cultivars (Pisum sativum L. cultivars Little Marvel, Perfection and Victory) grown in open-top chambers were exposed to either charcoal-filtered (FA) or non-filtered air (NF) for five consecutive years (2009–2013) at a rural site in northern Egypt. Net photosynthetic rates (P{sub N}), stomatal conductance (g{sub s}), intercellular CO{sub 2} (C{sub i}) and chlorophyll fluorescence were measured. Ozone (O{sub 3}) was found to be the most prevalent pollutant common at the rural site and is suspected to be involved in the alteration of the physiological parameters measured in the present investigation. P{sub N} of different cultivars were found to respond similarly; decreases of 23, 29 and 39% were observed in the cultivars Perfection, Little Marvel and Victory, respectively (averaged over the five years) due to ambient O{sub 3}. The maximum impairment in P{sub N} was recorded in the cultivar Victory (46%) in 2013 when the highest O{sub 3} levels were recorded (90 nL L{sup −1}). The average stomatal conductance decreased by 20 and 18% in the cultivars Little Marvel and Perfection, respectively, while the average stomatal conductance increased on average by 27% in the cultivar Victory. A significant correlation was found between P{sub N} and C{sub i}, indicating the importance of non-stomatal limitations of photosynthesis, especially in the cultivar Victory. The P{sub N} vs. Ci curves were fitted to a non-rectangular hyperbolic model. The actual quantum yield (Φ{sub PSII}) and photochemical quenching coefficient (qP) were significantly decreased in the leaves of plants exposed to NF air. Non-photochemical quenching (NPQ) was increased in all cultivars. Exposure to NF air caused reductions in chlorophyll (Chl a) of 19, 16 and 30% in the Little Marvel, Perfection and Victory cultivars, respectively. - Highlights: • Ozone (O{sub 3}) concentrations recorded were within the ranges of phytotoxicity. • O{sub 3} has a clear influence on the physiological

  4. Gas exchange and chlorophyll fluorescence of pea (Pisum sativum L.) plants in response to ambient ozone at a rural site in Egypt.

    Science.gov (United States)

    Ismail, I M; Basahi, J M; Hassan, I A

    2014-11-01

    Egyptian pea cultivars (Pisum sativum L. cultivars Little Marvel, Perfection and Victory) grown in open-top chambers were exposed to either charcoal-filtered (FA) or non-filtered air (NF) for five consecutive years (2009-2013) at a rural site in northern Egypt. Net photosynthetic rates (PN), stomatal conductance (gs), intercellular CO2 (Ci) and chlorophyll fluorescence were measured. Ozone (O3) was found to be the most prevalent pollutant common at the rural site and is suspected to be involved in the alteration of the physiological parameters measured in the present investigation. PN of different cultivars were found to respond similarly; decreases of 23, 29 and 39% were observed in the cultivars Perfection, Little Marvel and Victory, respectively (averaged over the five years) due to ambient O3. The maximum impairment in PN was recorded in the cultivar Victory (46%) in 2013 when the highest O3 levels were recorded (90 nL L(-1)). The average stomatal conductance decreased by 20 and 18% in the cultivars Little Marvel and Perfection, respectively, while the average stomatal conductance increased on average by 27% in the cultivar Victory. A significant correlation was found between PN and Ci, indicating the importance of non-stomatal limitations of photosynthesis, especially in the cultivar Victory. The PN vs. Ci curves were fitted to a non-rectangular hyperbolic model. The actual quantum yield (ΦPSII) and photochemical quenching coefficient (qP) were significantly decreased in the leaves of plants exposed to NF air. Non-photochemical quenching (NPQ) was increased in all cultivars. Exposure to NF air caused reductions in chlorophyll (Chl a) of 19, 16 and 30% in the Little Marvel, Perfection and Victory cultivars, respectively.

  5. Comparison of Sun-Induced Chlorophyll Fluorescence Estimates Obtained from Four Portable Field Spectroradiometers

    Directory of Open Access Journals (Sweden)

    Tommaso Julitta

    2016-02-01

    Full Text Available Remote Sensing of Sun-Induced Chlorophyll Fluorescence (SIF is a research field of growing interest because it offers the potential to quantify actual photosynthesis and to monitor plant status. New satellite missions from the European Space Agency, such as the Earth Explorer 8 FLuorescence EXplorer (FLEX mission—scheduled to launch in 2022 and aiming at SIF mapping—and from the National Aeronautics and Space Administration (NASA such as the Orbiting Carbon Observatory-2 (OCO-2 sampling mission launched in July 2014, provide the capability to estimate SIF from space. The detection of the SIF signal from airborne and satellite platform is difficult and reliable ground level data are needed for calibration/validation. Several commercially available spectroradiometers are currently used to retrieve SIF in the field. This study presents a comparison exercise for evaluating the capability of four spectroradiometers to retrieve SIF. The results show that an accurate far-red SIF estimation can be achieved using spectroradiometers with an ultrafine resolution (less than 1 nm, while the red SIF estimation requires even higher spectral resolution (less than 0.5 nm. Moreover, it is shown that the Signal to Noise Ratio (SNR plays a significant role in the precision of the far-red SIF measurements.

  6. Pico-projector-based optical sectioning microscopy for 3D chlorophyll fluorescence imaging of mesophyll cells

    Science.gov (United States)

    Chen, Szu-Yu; Hsu, Yu John; Yeh, Chia-Hua; Chen, S.-Wei; Chung, Chien-Han

    2015-03-01

    A pico-projector-based optical sectioning microscope (POSM) was constructed using a pico-projector to generate structured illumination patterns. A net rate of 5.8 × 106 pixel/s and sub-micron spatial resolution in three-dimensions (3D) were achieved. Based on the pico-projector’s flexibility in pattern generation, the characteristics of POSM with different modulation periods and at different imaging depths were measured and discussed. With the application of different modulation periods, 3D chlorophyll fluorescence imaging of mesophyll cells was carried out in freshly plucked leaves of four species without sectioning or staining. For each leaf, an average penetration depth of 120 μm was achieved. Increasing the modulation period along with the increment of imaging depth, optical sectioning images can be obtained with a compromise between the axial resolution and signal-to-noise ratio. After ∼30 min imaging on the same area, photodamage was hardly observed. Taking the advantages of high speed and low damages of POSM, the investigation of the dynamic fluorescence responses to temperature changes was performed under three different treatment temperatures. The three embedded blue, green and red light-emitting diode light sources were applied to observe the responses of the leaves with different wavelength excitation.

  7. Center for Fluorescence Spectroscopy: advanced studies of fluorescence dynamics, lifetime imaging, clinical sensing, two-photon excitation, and light quenching

    Science.gov (United States)

    Lakowicz, Joseph R.; Malak, Henryk M.; Gryczynski, Ignacy; Szmacinski, Henryk; Kusba, Jozef; Akkaya, Engin; Terpetschnig, Ewald A.; Johnson, Michael L.

    1994-08-01

    The Center for Fluorescence Spectroscopy (CFS) is a multi-user facility providing state of the art time-resolved fluorescence instrumentation and software for scientists, whose research can be enhanced by such experimental data. The CFS is a national center, supported by the National Center for Research Resources Division of the National Institutes of Health, and in part by the National Science Foundation. Both time-domain (TD) and frequency- domain (FD) measurements (10 MHz to 10 Ghz) are available, with a wide range of excitation and emission wavelengths (UV to NIR). The data can be used to recover distances and site-to-site diffusion in protein, interactions between macromolecules, accessibility of fluorophores to quenchers, and the dynamic properties of proteins, membranes and nucleic acids. Current software provides for analysis of multi-exponential intensity and anisotropy decays, lifetime distribution, distance distributions for independent observation of fluorescence donors and acceptors, transient effects in collisional quenching, phase-modulation spectra and time-resolved emission spectra. Most programs provide for global analysis of multiple data sets obtained under similar experimental conditions. Data can be analyzed on-site by connection with the CFS computers through the internet. During six years of operation we have established scientific collaborations with over 30 academic and industrial groups in the United States. These collaborations have resulted in 63 scientific papers.

  8. Folded or nonfolded fluorophores incorporating naphthalene:Their fluorescent quenching driven by charge transfer or co-aggregation in the aqueous-organic binary solvent

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Folded or nonfolded fluorophores incorporating naphthalene were synthesized and characterized by steady state fluorescence technique.Paraquat as an excellent quenching reagent quenched the fluorescence of Nel6 or nDs(n = 1-4) driven by charge transfer.Under aggregation of nDs,α-CD did not quench the fluorescence of 1D.At lower concentration,the quenching tendency ofα-CD against nDs is 2D>3D>4D,while at higher concentration,the tendency is 2D<3D<4D.α-CD showed the selective recognition on its fluorescent ...

  9. Chlorophyll Fluorescence and Photon Yield of Oxygen Evolution in Iron-Deficient Sugar Beet (Beta vulgaris L.) Leaves 12

    Science.gov (United States)

    Morales, Fermín; Abadía, Anunciación; Abadía, Javier

    1991-01-01

    The response of sugar beet (Beta vulgaris L.) leaves to iron deficiency can be described as consisting of two phases. In the first phase, leaves may lose a large part of their chlorophyll while maintaining a roughly constant efficiency of photosystem II photochemistry; ratios of variable to maximum fluorescence decreased by only 6%, and photon yields of oxygen evolution decreased by 30% when chlorophyll decreased by 70%. In the second phase, when chlorophyll decreased below a threshold level, iron deficiency caused major decreases in the efficiency of photosystem II photochemistry and in the photon yield of oxygen evolution. These decreases in photosystem II photochemical efficiency were found both in plants dark-adapted for 30 minutes and in plants dark-adapted overnight, indicating that photochemical efficiency cannot be repaired in that time scale. Decreases in photosystem II photochemical efficiency and in the photon yield of oxygen evolution were similar when measurements were made (a) with light absorbed by carotenoids and chlorophylls and (b) with light absorbed only by chlorophylls. Leaves of iron-deficient plants exhibited a room temperature fluorescence induction curve with a characteristic intermediate peak I that increases with deficiency symptoms. PMID:16668527

  10. 3个钓钟柳品种叶绿素荧光特性比较%Chlorophyll fluorescence parameters in three cultivars of Penstemon

    Institute of Scientific and Technical Information of China (English)

    陶文文; 蒋文伟; 赵丽娟

    2011-01-01

    The chlorophyll fluorescence parameters change of the Penstemon was studied, the aim was to enhance its planting management for the region in east China. Chlorophyll fluorescence parameters [minimal fluo rescence(Fo), maximum fluorescence (Fm), photochemical quenching (qp), variable fluorescence (Fv), yield (Y), non photochemical quenching (NPQ), and electron transport rate (ETR) ] of Penstemon campanulatus ‘Purple Passion' , Penstemon digitalis ‘Husker Red' , and Penstemon barbatus ‘Rondo' , all perennial root flowers, were measured and compared by the chlorophyll florescence measuring technique. A correlation analysis was conducted. Results of the correlation analysis showed significant positive correlations between Fo and Fm, qp and Fm, qp and Fv, Y and ETa, Fm and Fv, Fo and F, and Fm and Y; significantly negative correlations were found between Fo and ETR and Fv/Fo and Y. Also, chlorophyll fluorescence parameters for the three cultivars were significant(P < 0.05) and highly significant (P < 0.01 ). The values of Fv, Fv/Fm, Fv/Fo, Y,ETR, qp, and Nm for the three cultivars were in the order: ‘Purple Passion' > ‘Rondo' > ‘Husker Red'. Thus, the photosynthetic physiological functions of P. campanulatus ‘Purple Passion' were best.%利用叶绿素荧光测定技术测定了多年生宿根花卉紫红钓钟柳penstemon campanulatus'Purple Passion',毛地黄钓钟柳P.digitalis'Husker Red'和五彩钓钟柳P.barbatus'Rondo'等3个钓钟柳品种的叶绿素荧光参数,并对它们进行比较.结果表明:3个钓钟柳品种间的叶绿素荧光参数均达到显著或极显著水平,紫红钓钟柳的可变荧光(Fv),光系统Ⅱ原始光能转化效率(Fv/Fm),光系统Ⅱ的潜在活性(Fv/Fo),光合量子产额(Y),表观光合电子传递速率(ETR),光化学猝灭系数(qp),非炮化学猝灭系数(NPQ)值最高,其次为五彩钓钟柳,最低是毛地黄钓钟柳.说明紫红钓钟柳具有较好的光合生理功能,其次是五彩钓钟

  11. Solvatochromic study of highly fluorescent alkylated isocyanonaphthalenes, their π-stacking, hydrogen-bonding complexation, and quenching with pyridine.

    Science.gov (United States)

    Nagy, Miklós; Rácz, Dávid; Lázár, László; Purgel, Mihály; Ditrói, Tamás; Zsuga, Miklós; Kéki, Sándor

    2014-11-10

    Mono- and dialkylated derivatives of 1-amino-5-isocyanonaphthalene (ICAN) were studied as new members of a multifunctional, easy-to-prepare fluorophore family, which showed excellent solvatochromic properties. The monoallyl derivative and the starting ICAN exhibited strong fluorescence quenching in the presence of small amounts of pyridine. The formation of a hydrogen-bonded ground-state pyridine complex was detected; however, analysis of quantum chemical calculations suggested the presence of an additional π-stacked pyridine complex. The Stern-Volmer plot of the quenching process exhibited a downward curvature and after reaching a minimum the fluorescence intensity increased back to a significant level at high pyridine concentrations. Significant fluorescence was observed even in pure pyridine. A new mechanism and a simple mathematical equation were derived to explain the downward curvature and the remaining fluorescence by the formation of a fluorescent π-stacked complex.

  12. Chlorophyll Fluorescence in Partially Defoliated Grape Plants (Vitis vinifera L. cv. Chardonnay / Fluorescencia de la Clorofila en Plantas de Uva (Vitis vinifera L. cv. Chardonnay Defoliadas Parcialmente

    Directory of Open Access Journals (Sweden)

    Peña Olmos Jaime Ernesto

    2013-08-01

    Full Text Available The chlorophyll content and fluorescence weredetermined in five-year-old grape plants (Vitis vinifera L. cv.Chardonnay that were subjected to early partial defoliation,in Villa de Leyva, Colombia. The experimental design wascompletely randomized, consisting of two treatments (50%defoliation and control, each with four replications of 35 plants. Every two weeks, one of every two recently-emerged leaves was removed from the non-control plants. The determination of total chlorophyll content was carried out on six leaves per plant using a CCM-200 Plus chlorophyll meter, while chlorophyll fluorescence measurements were taken with one darkadapted leaf per plant using a Junior-PAM fluorometer. Initial fluorescence (Fo, maximum fluorescence (Fm, terminal fluorescence (Ft, variable fluorescence (Fv, electron transport rate (ETR, maximum photochemical quantum yield of PSII (Fv/ Fm, effective photochemical quantum yield of photosystem II (Y(II, photochemical fluorescence quenching coefficient (qP, two non-photochemical quenching coefficients (qN and NPQ,quantum yield of light-induced non-photochemical fluorescence quenching (Y(NPQ, and quantum yield of non-light-induced non-photochemical quenching (Y(NO were measured. The chlorophyll concentration index showed higher values in the defoliated plants. There were no significant differences for the values of Fm, Ft and Fv. Fo was higher in the defoliated plants, while ETR, Fv/Fm and Y(II showed higher values in the control plants. It is evident that a reduction in leaf area modifies thepartitioning of excitation energy destined for photochemicaland non-photochemical processes, thus directly influencing the photosynthetic process of the plants evaluated. / Utilizando un diseño completamente aleatorizado,con dos tratamientos (defoliación al 50% y control y cuatrorepeticiones de 35 plantas cada una, se determinó el contenido y la fluorescencia de la clorofila en plantas de uva, sometidas a defoliación parcial

  13. Fluorescence quenching of CdS quantum dots by 4-azetidinyl-7-nitrobenz-2-oxa-1,3-diazole: a mechanistic study.

    Science.gov (United States)

    Santhosh, Kotni; Patra, Satyajit; Soumya, S; Khara, Dinesh Chandra; Samanta, Anunay

    2011-10-24

    Fluorescence quenching of CdS quantum dots (QDs) by 4-azetidinyl-7-nitrobenz-2-oxa-1,3-diazole (NBD), where the two quenching partners satisfy the spectral overlap criterion necessary for Förster resonance energy transfer (FRET), is studied by steady-state and time-resolved fluorescence techniques. The fluorescence quenching of the QDs is accompanied by an enhancement of the acceptor fluorescence and a reduction of the average fluorescence lifetime of the donor. Even though these observations are suggestive of a dynamic energy transfer process, it is shown that the quenching actually proceeds through a static interaction between the quenching partners and is probably mediated by charge-transfer interactions. The bimolecular quenching rate constant estimated from the Stern-Volmer plot of the fluorescence intensities, is found to be exceptionally high and unrealistic for the dynamic quenching process. Hence, a kinetic model is employed for the estimation of actual quencher/QD ratio dependent exciton quenching rate constants of the fluorescence quenching of CdS by NBD. The present results point to the need for a deeper analysis of the experimental quenching data to avoid erroneous conclusions.

  14. A comparative study on fluorescence quenching of CdTe nanocrystals with a serial of polycyclic aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Baslak, Canan, E-mail: cananbaslak@gmail.com [Advanced Technology Research and Application Center, Selcuk University, 42075 Konya (Turkey); Department of Chemistry, Faculty of Science, Selcuk University, 42075 Konya (Turkey); Kus, Mahmut, E-mail: mahmutkus1@gmail.com [Advanced Technology Research and Application Center, Selcuk University, 42075 Konya (Turkey); Department of Chemical Engineering, Faculty of Engineering, Selcuk University, 42075 Konya (Turkey); Cengeloglu, Yunus [Department of Chemistry, Faculty of Science, Selcuk University, 42075 Konya (Turkey); Ersoz, Mustafa [Advanced Technology Research and Application Center, Selcuk University, 42075 Konya (Turkey); Department of Chemistry, Faculty of Science, Selcuk University, 42075 Konya (Turkey)

    2014-09-15

    We report sensing different polycyclic aromatic hydrocarbons (PAHs) with colloidal CdTe nanocrystals. The effect of molecular structure on quenching rate for 2-hyroxy-1-naphthaldehyde (2H–1N), 9,10-phenanthraquinone (PQ), 9-anthracenecarboxaldehyde (9-AC) and quinoline (Q) is presented. The quenching rate constants are observed to be strongly dependent on the molecular structure. PQ, consisting of two carbonyl groups, shows the highest rate constant while Q shows the worst one. Both static and dynamic quenching are simultaneously observed for PQ and 2H–1N. Therefore extended Stern–Volmer equations are used to calculate rate constants. Results showed that dynamic quenching is a dominant process. The rate constants for PQ, 2H–1N, 9-AC and Q are calculated to be 64.84, 10.73, 10.66 and 1.85 respectively. - Highlights: • We report the fluorescence quenching of colloidal CdTe nanocrystals with different polycyclic aromatic hydrocarbons. • The quenching rate constants are observed to be strongly dependent on the molecular structure. • Static and dynamic quenching are simultaneously observed. • The best quenching was observed for 9,10-phenanthraquinone.

  15. Which model based on fluorescence quenching is suitable to study the interaction between trans-resveratrol and BSA?

    Science.gov (United States)

    Wei, Xin Lin; Xiao, Jian Bo; Wang, Yuanfeng; Bai, Yalong

    2010-01-01

    There are several models by means of quenching fluorescence of BSA to determine the binding parameters. The binding parameters obtained from different models are quite different from each other. Which model is suitable to study the interaction between trans-resveratrol and BSA? Herein, twelve models based fluorescence quenching of BSA were compared. The number of binding sites increasing with increased binding constant for similar compounds binding to BSA maybe one approach to resolve this question. For example, here eleven flavonoids were tested to illustrate that the double logarithm regression curve is suitable to study binding polyphenols to BSA.

  16. Identification of the sites of chlorophyll triplet quenching in relation to the structure of LHC-II from higher plants. Evidence from EPR spectroscopy.

    Science.gov (United States)

    Di Valentin, Marilena; Biasibetti, Federico; Ceola, Stefano; Carbonera, Donatella

    2009-10-01

    The Chlorophyll a (Chl a) molecules involved in the triplet-triplet energy transfer to the central luteins in trimeric LHC-II are identified by time-resolved and pulse EPR techniques. The concept of spin angular momentum conservation during triplet-triplet energy transfer is exploited for the calculation of the spin polarization of the carotenoid triplet states. The sites with the highest probability of forming triplet states, which are quenched by the central luteins, result to be Chl603 and Chl612. "Unquenched" Chl triplet states are produced by photoexcitation in the LHC-II complex. Putative sites of these triplet states are Chl614, Chl611, Chl604, and Chl613 since they do not contribute to the formation of the observed carotenoid triplet states.

  17. Fiber-optic fluorescence-quenching oxygen partial pressure sensor using platinum octaethylporphyrin.

    Science.gov (United States)

    Davenport, John J; Hickey, Michelle; Phillips, Justin P; Kyriacou, Panayiotis A

    2016-07-20

    The development and bench testing of a fiber-optic oxygen sensor is described. The sensor is designed for measurement of tissue oxygen levels in the mucosa of the digestive tract. The materials and construction are optimized for insertion through the mouth for measurement in the lower esophagus. An oxygen-sensitive fluorescence-quenching film was applied as a solution of platinum octaethylporphyrin (PtOEP) poly(ethyl methacrylate) (PEMA) and dichloromethane and dip coated onto the distal tip of the fiber. The sensor was tested by comparing relative fluorescence when immersed in liquid water at 37°C, at a range of partial pressures (0-101 kPa). Maximum relative fluorescence at most oxygen concentrations was seen when the PtOEP concentration was 0.1  g.L-1, four layers of coating solution were applied, and a fiber core radius of 600 μm was selected, giving a Stern-Volmer constant of 0.129  kPa-1. The performance of the sensor is suitable for many in vivo applications, particularly mucosal measurements. It has sufficient sensitivity, is sterilizable, and is sufficiently flexible and robust for insertion via the mouth without damage to the probe or risk of harm to the patient.

  18. Complexation of fluoroquinolone antibiotics with human serum albumin: A fluorescence quenching study

    Energy Technology Data Exchange (ETDEWEB)

    Seedher, Neelam, E-mail: nseedher@yahoo.co [Department of Chemistry, Panjab University, Chandigarh 160014 (India); Agarwal, Pooja [Department of Chemistry, Panjab University, Chandigarh 160014 (India)

    2010-10-15

    Mechanism of interaction and detailed physico-chemical characterization of the binding of four fluoroquinolones: levofloxacin, sparfloxacin, ciprofloxacin HCl and enrofloxacin with human serum albumin has been studied at physiological pH (7.4) using fluorescence spectroscopic technique. The stoichiometry of interaction was found to be 1:1 for all the drugs used. The association constants for the interaction were of the order of 10{sup 4} in most cases. At low drug:protein ratios, a significant fraction of the added drug was bound. The predominant interactions involved are hydrogen bonding and Van der Waal's interactions in the case of levofloxacin, hydrophobic interactions in the case of ciprofloxacin hydrochloride and enrofloxacin and hydrogen bonding, hydrophobic and electrostatic interactions in the case of sparfloxacin. The drug binding region did not coincide with that of the hydrophobic probe, 1-anilinonaphthalene-8-sulfonate (ANS). From the displacement of site-specific probes and site-marker drugs, it was concluded that ciprofloxacin hydrochloride is site II-specific while enrofloxacin is a site I-specific drug. Levofloxacin binds at both site I and site II with equal affinity. Sparfloxacin had higher affinity for site II than site I. It is also possible that sparfloxacin binds at the interface between site I and site II. Stern-Volmer analysis of the data showed that the quenching mechanism is predominantly collisional for the binding of ciprofloxacin HCl and enrofloxacin while both static and collisional quenching mechanisms are operative in the case of levofloxacin and sparfloxacin. High magnitude of the rate constant for quenching showed that the process is not entirely diffusion controlled. Circular dichroism (CD) spectroscopic studies showed that the presence of drugs did not cause any major changes in the secondary structure of HSA.

  19. Fluorescence quenching and spectrophotometric methods for the determination of daunorubicin with meso-tera (4-sulphophenyl) porphyrin as probe.

    Science.gov (United States)

    Tian, Jing; Liu, Shaopu; Liu, Zhongfang; Yang, Jidong; Zhu, Jinghui; Qiao, Man; Hu, Xiaoli

    2014-01-01

    In this work, a synthetic meso-tera (4-sulfophenyl) porphyrin (TPPS4) was used as a probe to determine daunorubicin (DNR) by fluorescence quenching and spectrophotometric methods. At pH 4.6 potassium acid phthalate-NaOH buffer solution, a 1:1 complex of DNR interacted with TPPS4 formed via the electrostatic attractions and hydrophobic interactions, thus resulted in TPPS4 fluorescence quenching and absorption spectra change. The maximum excitation wavelength (λex) and the maximum emission wavelength (λem) are 435 nm and 672 nm, respectively. The fluorescence quenching values (ΔF) are the good linear relationship to the concentration of DNR in the range of 0.8-6.0 mgL(-1). The method exhibits high sensitivity with the detection limit (3σ) being 27.0 ng mL(-1). Meanwhile, a decrease of absorbance is detected at 433 nm with the appearance of a new absorption peak at 420 nm. The optimum reaction conditions, influencing factors and the effect of coexisting substances have been investigated in our experiment. The results showed that the method had a good selectivity and could be applied to determine DNR in serum and urine samples. In addition, the combine ratio between DNR and TPPS4 was measured and the charge distribution before and after reaction was calculated by quantum chemistry calculation AM1 method. The type of fluorescence quenching was discussed by the absorption spectra change, Stern-Volmer plots and fluorescence lifetime determination.

  20. Multiplex fluorescence melting curve analysis for mutation detection with dual-labeled, self-quenched probes.

    Directory of Open Access Journals (Sweden)

    Qiuying Huang

    Full Text Available Probe-based fluorescence melting curve analysis (FMCA is a powerful tool for mutation detection based on melting temperature generated by thermal denaturation of the probe-target hybrid. Nevertheless, the color multiplexing, probe design, and cross-platform compatibility remain to be limited by using existing probe chemistries. We hereby explored two dual-labeled, self-quenched probes, TaqMan and shared-stem molecular beacons, in their ability to conduct FMCA. Both probes could be directly used for FMCA and readily integrated with closed-tube amplicon hybridization under asymmetric PCR conditions. Improved flexibility of FMCA by using these probes was illustrated in three representative applications of FMCA: mutation scanning, mutation identification and mutation genotyping, all of which achieved improved color-multiplexing with easy probe design and versatile probe combination and all were validated with a large number of real clinical samples. The universal cross-platform compatibility of these probes-based FMCA was also demonstrated by a 4-color mutation genotyping assay performed on five different real-time PCR instruments. The dual-labeled, self-quenched probes offered unprecedented combined advantage of enhanced multiplexing, improved flexibility in probe design, and expanded cross-platform compatibility, which would substantially improve FMCA in mutation detection of various applications.

  1. Influence of the excitation light intensity on the rate of fluorescence quenching reactions: pulsed experiments.

    Science.gov (United States)

    Angulo, Gonzalo; Milkiewicz, Jadwiga; Kattnig, Daniel; Nejbauer, Michał; Stepanenko, Yuriy; Szczepanek, Jan; Radzewicz, Czesław; Wnuk, Paweł; Grampp, Günter

    2017-02-22

    The effect of multiple light excitation events on bimolecular photo-induced electron transfer reactions in liquid solution is studied experimentally. It is found that the decay of fluorescence can be up to 25% faster if a second photon is absorbed after a first cycle of quenching and recombination. A theoretical model is presented which ascribes this effect to the enrichment of the concentration of quenchers in the immediate vicinity of fluorophores that have been previously excited. Despite its simplicity, the model delivers a qualitative agreement with the observed experimental trends. The original theory by Burshtein and Igoshin (J. Chem. Phys., 2000, 112, 10930-10940) was created for continuous light excitation though. A qualitative extrapolation from the here presented pulse experiments to the continuous excitation conditions lead us to conclude that in the latter the order of magnitude of the increase of the quenching efficiency upon increasing the light intensity of excitation, must also be on the order of tens of percent. These results mean that the rate constant for photo-induced bimolecular reactions depends not only on the usual known factors, such as temperature, viscosity and other properties of the medium, but also on the intensity of the excitation light.

  2. Study of Interaction Between Tryptophan, Tyrosine, and Phenylalanine Separately with Silver Nanoparticles by Fluorescence Quenching Method

    Science.gov (United States)

    Roy, S.; Das, T. K.

    2015-09-01

    Using the spectroscopic method, the individual interaction of the three biochemically important amino acids, which are constituents of protein, namely, tryptophan, tyrosine, and phenylalanine with biologically synthesized silver nanoparticles has been investigated. The obtained UV-Vis spectra show the formation of ground-state complexes between tryptophan, tyrosine, and phenylalanine with silver nanoparticles. Silver nanoparticles possess the ability to quench the intrinsic fluorescence of the aforesaid amino acids by a dynamic quenching process. The binding constant, number of binding sites, and corresponding thermodynamic parameters (Δ H, Δ S, and Δ G) based on the interaction system were calculated for 293, 303, and 313 K. In the case of tryptophan and phenylalanine, with increase in temperature, the binding constant K was found to decrease; conversely, it was found to increase with increase in temperature in the case of tyrosine. The thermodynamic results revealed that the binding process was spontaneous; hydrogen bonding and van der Waals interaction were the predominant forces responsible for the complex stabilization in the case of tryptophan and phenylalanine, respectively, whereas in the case of tyrosine, hydrophobic interaction was the sole force conferring stability. Moreover, the Förster non-radiation energy transfer theory has been applied to calculate the average binding distance among the above amino acids and silver nanoparticles. The results show a binding distance of <7 nm, which ensures that energy transfer does occur between the said amino acids and silver nanoparticles.

  3. A High-Performance Fluorescence Immunoassay Based on the Relaxation of Quenching, Exemplified by Detection of Cardiac Troponin I

    Directory of Open Access Journals (Sweden)

    Seung-Wan Kim

    2016-05-01

    Full Text Available The intramolecular fluorescence self-quenching phenomenon is a major drawback in developing high-performance fluorometric biosensors which use common fluorophores as signal generators. We propose two strategies involving liberation of the fluorescent molecules by means of enzymatic fragmentation of protein or dehybridization of double-stranded DNA. In the former, bovine serum albumin (BSA was coupled with the fluorescent BODIPY dye (Red BSA, and then immobilized on a solid surface. When the insolubilized Red BSA was treated with proteinase K (10 units/mL for 30 min, the fluorescent signal was significantly increased (3.5-fold compared to the untreated control. In the second case, fluorophore-tagged DNA probes were linked to gold nanoparticles by hybridization with capture DNA strands densely immobilized on the surface. The quenched fluorescence signal was recovered (3.7-fold by thermal dehybridization, which was induced with light of a specific wavelength (e.g., 530 nm for less than 1 min. We next applied the Red BSA self-quenching relaxation technique employing enzymatic fragmentation to a high-performance immunoassay of cardiac troponin I (cTnI in a microtiter plate format. The detection limit was 0.19 ng/mL cTnI, and the fluorescent signal was enhanced approximately 4.1-fold compared with the conventional method of direct measurement of the fluorescent signal from a non-fragmented fluorophore-labeled antibody.

  4. [Fluorescence quenching method for the determination of p-hydroxyphenylpyruvic acid].

    Science.gov (United States)

    Wu, F; Fu, M; Wei, X; Yang, W; Hu, R; Guo, L

    2001-06-01

    A fluorescence quenching method for the determination of p-hydroxyphenylpyruvic acid with trytophan in the medium pH 11.01 NH3-NH4Cl is studied. The calibration curve is linear for p-hydroxyphenylpyruvic acid from 0 to 15 micrograms.mL-1 with lambda ex/lambda em = 285/356 nm. The detection limit is 0.37 microgram.mL-1. Twenty replicate determinations of solutions containing 10 micrograms.mL-1 p-hydroxyphenylpyruvic acid show a relative standard deviation of 1.2%. This method can be applied to the determination of p-hydroxyphenylpyruvic acid in serum with satisfactory results.

  5. Estimating chlorophyll content and photochemical yield of photosystem II (ΦPSII) using solar-induced chlorophyll fluorescence measurements at different growing stages of attached leaves.

    Science.gov (United States)

    Tubuxin, Bayaer; Rahimzadeh-Bajgiran, Parinaz; Ginnan, Yusaku; Hosoi, Fumiki; Omasa, Kenji

    2015-09-01

    This paper illustrates the possibility of measuring chlorophyll (Chl) content and Chl fluorescence parameters by the solar-induced Chl fluorescence (SIF) method using the Fraunhofer line depth (FLD) principle, and compares the results with the standard measurement methods. A high-spectral resolution HR2000+ and an ordinary USB4000 spectrometer were used to measure leaf reflectance under solar and artificial light, respectively, to estimate Chl fluorescence. Using leaves of Capsicum annuum cv. 'Sven' (paprika), the relationships between the Chl content and the steady-state Chl fluorescence near oxygen absorption bands of O2B (686nm) and O2A (760nm), measured under artificial and solar light at different growing stages of leaves, were evaluated. The Chl fluorescence yields of ΦF 686nm/ΦF 760nm ratios obtained from both methods correlated well with the Chl content (steady-state solar light: R(2) = 0.73; artificial light: R(2) = 0.94). The SIF method was less accurate for Chl content estimation when Chl content was high. The steady-state solar-induced Chl fluorescence yield ratio correlated very well with the artificial-light-induced one (R(2) = 0.84). A new methodology is then presented to estimate photochemical yield of photosystem II (ΦPSII) from the SIF measurements, which was verified against the standard Chl fluorescence measurement method (pulse-amplitude modulated method). The high coefficient of determination (R(2) = 0.74) between the ΦPSII of the two methods shows that photosynthesis process parameters can be successfully estimated using the presented methodology.

  6. Fluorescence lifetime and acrylamide quenching studies of the interactions between troponin subunits.

    Science.gov (United States)

    Leavis, P C; Gowell, E; Tao, T

    1984-08-28

    Fluorescence lifetime and acrylamide quenching studies were carried out to characterize the interactions between the subunits of troponin under various conditions of metal ion binding. Troponin C was labeled at Cys-98 with N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)ethylenediamine. In the presence of Ca2+, the fluorescence decay of labeled troponin C (TnC*) was monoexponential, lifetime tau = 15.5 ns and quenching rate constant kq = 2.97 X 10(8) M-1 s-1. In the absence of Ca2+, the decay was resolvable into a major component with tau = 11.9 ns and a minor component with tau = 20.5 ns, with corresponding values of kq = 4.80 X 10(8) and 0.66 X 10(8) M-1 s-1, respectively. Upon the binding of either troponin I (TnI) or troponin T (TnT) in the presence of Ca2+, tau increased to approximately 18 ns, and kq decreased to approximately 0.8 X 10(8) M-1 s-1. For the Ca2+ form of the TnC*-TnI-TnT ternary complex, values of tau = 17.6 ns and kq = 1.73 X 10(8) M-1 s-1 were obtained. These values did not vary significantly when Ca2+ was removed, or when Mg2+ replaced Ca2+. These findings were interpreted as follows: the region around Cys-98 of TnC* adopts a looser conformation upon the removal of Ca2+ from the high-affinity sites. Both TnI and TnT bind to TnC* in the region containing Cys-98. The probe is shielded from the solvent to a greater extent in the binary complexes than in the ternary complex.(ABSTRACT TRUNCATED AT 250 WORDS)

  7. Fluorescence-quenching study of glucose binding by yeast hexokinase isoenzymes

    Energy Technology Data Exchange (ETDEWEB)

    Feldman, I.; Kramp, D.C.

    1978-04-18

    A study of the effect of varying ionic strength on the glucose-induced quenching of tryptophan fluorescence of hexokinase isoenzymes A(P-I) and B(P-II) was carried out at pH 8.3 and pH 5.5. At pH 8.3 both isoenzymes gave apparently linear Scatchard-type data plots even with protein concentrations and ionic strengths for which both dimeric and monomeric forms of hexokinase coexist in significant amounts. Taking into account a 1 percent accuracy in the experimental measurements, we concluded that the intrinsic dissociation constants, K/sub M/ and K/sub D/, for the binding of glucose to the monomeric and dimeric forms of HkB, are within a factor of two of each other, i.e., K/sub D//K/sub M/ equal to or less than 2. The values of K/sub M/, estimated from the apparent K, were so greatly influenced by ionic strength that it is clear that it is meaningless to compare K/sub M/ and K/sub D/ values measured at different ionic strengths as has been done in the literature. Curvature in the pH 5.5 fluorescence-quenching plots for relatively low ionic strengths demonstrates cooperativity for glucose-binding to the dimer, positive for HkA but negative for HkB. In contrast, the binding is relatively noncooperative at high ionic strength at this pH. These results were attributed to the well known effect of salt-neutralization of side chain electrical charges on the flexibility and compactness of proteins.

  8. Effects of Dihydroartemisinin and Artemether on the Growth, Chlorophyll Fluorescence, and Extracellular Alkaline Phosphatase Activity of the Cyanobacterium Microcystis aeruginosa

    Science.gov (United States)

    Wang, Shoubing; Xu, Ziran

    2016-01-01

    Increased eutrophication in the recent years has resulted in considerable research focus on identification of methods for preventing cyanobacterial blooms that are rapid and efficient. The objectives of this study were to investigate the effects of dihydroartemisinin and artemether on the growth of Microcystis aeruginosa and to elucidate its mode of action. Variations in cell density, chlorophyll a, soluble protein, malondialdehyde, extracellular alkaline phosphatase activity (APA), and chlorophyll fluorescence parameters (Fv/Fm, ΦPSII, ETR, rapid light curves, fast chlorophyll fluorescence curves on fluorescence intensity, and relative variable fluorescence) were evaluated by lab-cultured experiments. Our results demonstrated that both dihydroartemisinin and artemether inhibited the growth of M.aeruginosa by impairing the photosynthetic center in photosystem II and reducing extracellular APA, with a higher sensitivity exhibited toward artemether. The inhibitory effects of dihydroartemisinin on M.aeruginosa increased with concentration, and the maximum growth inhibitory rate was 42.17% at 24 mg·L-1 after 120h exposure, whereas it was 55.72% at 6 mg·L-1 artemetherafter 120h exposure. Moreover, the chlorophyll fluorescence was significantly inhibited (p<0.05) after 120h exposure to 12 and 24 mg·L-1 dihydroartemisinin. Furthermore, after 120h exposure to 6 mg·L-1 artemether, Fv/Fm, ΦPSII, ETR and rETRmax showed a significant decrease (p<0.01) from initial values of 0.490, 0.516, 17.333, and 104.800, respectively, to 0. One-way analysis of variance showed that 6 mg·L-1 artemether and 24 mg·L-1 dihydroartemisinin had significant inhibitory effects on extracellular APA (p<0.01). The results of this study would be useful to further studies to validate the feasibility of dihydroartemisinin and artemether treatment to inhibit overall cyanobacterial growth in water bodies, before this can be put into practice. PMID:27755566

  9. Intracellular Disassembly of Self-Quenched Nanoparticles Turns NIR Fluorescence on for Sensing Furin Activity in Cells and in Tumors.

    Science.gov (United States)

    Yuan, Yue; Zhang, Jia; Cao, Qinjingwen; An, Linna; Liang, Gaolin

    2015-06-16

    There has been no report on enzyme-controlled disassembly of self-quenched NIR fluorescent nanoparticles turning fluorescence on for specific detection/imaging of the enzyme's activity in vitro and in vivo. Herein, we reported the rational design of new NIR probe 1 whose fluorescence signal was self-quenched upon reduction-controlled condensation and subsequent assembly of its nanoparticles (i.e., 1-NPs). Then disassembly of 1-NPs by furin turned the fluorescence on. Employing this enzymatic strategy, we successfully applied 1-NPs for NIR detection of furin in vitro and NIR imaging furin activity in living cells. Moreover, we also applied 1-NPs for discriminative NIR imaging of MDA-MB-468 tumors in nude mice. This NIR probe 1 might be further developed for tumor-targeted imaging in routine preclinical studies or even in patients in the future.

  10. Effects of Shading Stress and Light Recovery on the Photosynthesis Characteristic and Chlorophyll Fluorescence Characteristic of Fragaria Ananassa Duch. cv. Toyonoka

    Directory of Open Access Journals (Sweden)

    Renyan Duan

    2013-06-01

    Full Text Available Light is an important resource for plant growth and development, crops need to change their physiological characteristics to different light environments. Fragaria ananassa Duch. cv. Toyonoka. is an important economic plant which is widely planted at home. A greenhouse experiment was conducted from April 2010 with different sun-shading treatment, 85% (CK, 60% (T1, 35% (T2 and 10% (T3. After 7 days of shading stress, the physiological characteristics were slowly recovered. The results showed that (1 Under shading condition, Light saturation rate (Amax, Apparent Quantum Yield (AQY, Carboxylation Efficiency (CE, dark respiration (Rd, Light Saturation Point (LSP and Light Compensation Point (LCP became lower. (2 The maximal fluorescence (Fm, light energy transformation efficiency of PS II (Fv/Fm, actual photochemical efficiency of PS II in the light (Yield, photochemical quenching coefficient (qP declined with shading stress increase. (3 There were significant difference in the chlorophyll fluorescence parameters among different treatment groups by the end of sun-shading treatment (p<0.05. After the light was recovered, the physiological characteristics could rapidly recover under low shading stress and moderate shading stress, while in severe shading stress the physiological characteristics hardly recover.

  11. Global and Time-Resolved Monitoring of Crop Photosynthesis with Chlorophyll Fluorescence

    Science.gov (United States)

    Guanter, Luis; Zhang, Yongguang; Jung, Martin; Joiner, Joanna; Voigt, Maximilian; Berry, Joseph A.; Frankenberg, Christian; Huete, Alfredo R.; Zarco-Tejada, Pablo; Lee, Jung-Eun; Moran, M. Susan; Ponce-Campos, Guillermo; Beer, Christian; Camps-Valls, Gustavo; Buchmann, Nina; Gianelle, Damiano; Klumpp, Katja; Cescatti, Alessandro; Baker, John M.; Griffis, Timothy J.

    2014-01-01

    Photosynthesis is the process by which plants harvest sunlight to produce sugars from carbon dioxide and water. It is the primary source of energy for all life on Earth; hence it is important to understand how this process responds to climate change and human impact. However, model-based estimates of gross primary production (GPP, output from photosynthesis) are highly uncertain, in particular over heavily managed agricultural areas. Recent advances in spectroscopy enable the space-based monitoring of sun-induced chlorophyll fluorescence (SIF) from terrestrial plants. Here we demonstrate that spaceborne SIF retrievals provide a direct measure of the GPP of cropland and grassland ecosystems. Such a strong link with crop photosynthesis is not evident for traditional remotely sensed vegetation indices, nor for more complex carbon cycle models. We use SIF observations to provide a global perspective on agricultural productivity. Our SIF-based crop GPP estimates are 50-75% higher than results from state-of-the-art carbon cycle models over, for example, the US Corn Belt and the Indo-Gangetic Plain, implying that current models severely underestimate the role of management. Our results indicate that SIF data can help us improve our global models for more accurate projections of agricultural productivity and climate impact on crop yields. Extension of our approach to other ecosystems, along with increased observational capabilities for SIF in the near future, holds the prospect of reducing uncertainties in the modeling of the current and future carbon cycle.

  12. 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.

  13. Assessment of phytotoxicity of anthracene in soybean (Glycine max) with a quick method of chlorophyll fluorescence.

    Science.gov (United States)

    Tomar, R S; Sharma, A; Jajoo, A

    2015-07-01

    A decrease in photosynthetic efficiency may indicate the toxic effects of environmental pollutants on higher plants. Measurement of chlorophyll (Chl) a fluorescence to assess the performance of photosystem II (PSII) was used as an bioindicator of toxicity of the polycyclic aromatic hydrocarbon (PAH) anthracene (ANT) in soybean plants. The results revealed that ANT treatment caused a reduction in quantum yield of PSII, damage to the oxygen evolving complex, as well as a significant reduction in performance index of PSII. However, change in performance index was more prominent, and it seems that the performance index is a more sensitive parameter to environmental contaminants. Moreover, a change in heterogeneity of PSII was also observed. The number of active reaction centres decreased with increasing concentration of ANT, as secondary plastoquinone reducing centres were converted into non-reducing centres, and PSIIα centres were converted into PSIIβ and PSIIγ centres. The influence of ANT on PSII heterogeneity could be an important reason for reductions in the PSII performance.

  14. CO2, CH4, CO and Chlorophyll Fluorescence Retrievals for the Geostationary Carbon Process Investigation

    Science.gov (United States)

    Xi, X.; Natraj, V.; Luo, M.; Shia, R.; Sander, S. P.; Yung, Y. L.

    2013-12-01

    The Geostationary Carbon Process Investigation (GCPI) combines an imaging Fourier Transform Spectrometer instrument with a geostationary Earth orbit vantage point to realize a transformational advance in carbon monitoring beyond the synoptic capabilities of Low Earth Orbit instruments such as SCIAMACHY, GOSAT and OCO-2. GCPI follows the paradigm of numerical weather prediction and aims to provide orders of magnitude improvement in observational density for atmospheric CO2, CH4, CO, and new measurements of chlorophyll fluorescence (CF). These new observations could be used to drive and constrain Earth system models, improve our understanding of the underlying carbon cycle processes and evaluate model forecasting capabilities. GCPI is designed to deliver simultaneous measurements of CF and column averaged CO2, CH4 and CO dry air mole fractions to disentangle biogenic and anthropogenic sources of carbon. Here, we perform radiative transfer simulations over a range of conditions expected to be observed by GCPI and estimate prospective performance of retrievals based on results from Bayesian error analysis and characterizations. The potential benefits from the measurements of CF are also investigated.

  15. Validation of the chlorophyll fluorescence imaging method (CFI for early detection of herbicide resistance in weeds

    Directory of Open Access Journals (Sweden)

    Menegat, Alexander

    2014-02-01

    Full Text Available The increasing number of herbicide tolerant weed populations is illustrating the increasing demand for reliable methods for an accelerated detection of herbicide tolerance compared to greenhouse studies. Several methods for resistance quick detection have been published in previous years. One of the recent methods is the Chlorophyll Fluorescence Imaging Method (CFI. For this method changes in photosynthetic activity of the target organisms, caused by herbicides, are determined. General assumption of this method in terms of herbicide resistance detection is that each herbicidal compound, independent of the mode of action, will cause changes within the photosynthetic apparatus of the target organisms. This effect already could be confirmed for several modes of action (PSII, ALS, ACCase, EPSPS, synth. Auxins. Aim of this study is to validate this novel method on the basis of greenhouse experiments and single nucleotide polymorphisms (SNP analysis. The resistance profiles of 10 black-grass populations (Alopecurus myosuroides Huds. have been determined in greenhouse herbicide efficacy trials and constitutive SNP analyses of the survivors. With the CFI-method it was possible to detect the resistance profile as well as the resistance frequency within the populations. The results from the greenhouse experiments could be reproduced with conformity of 94%. This result is valid for the tested herbicides mesosulfuron, pyroxsulam as well as clodinafop and pinoxaden.

  16. Analysis of chlorophyll fluorescence reveals stage specific patterns of chloroplast-containing cells during Arabidopsis embryogenesis.

    Science.gov (United States)

    Tejos, Ricardo I; Mercado, Ana V; Meisel, Lee A

    2010-01-01

    The basic body plan of a plant is established early in embryogenesis when cells differentiate, giving rise to the apical and basal regions of the embryo. Using chlorophyll fluorescence as a marker for chloroplasts, we have detected specific patterns of chloroplast-containing cells at specific stages of embryogenesis. Non-randomly distributed chloroplast-containing cells are seen as early as the globular stage of embryogenesis in Arabidopsis. In the heart stage of embryogenesis, chloroplast containing cells are detected in epidermal cells as well as a central region of the heart stage embryo, forming a triangular septum of chloroplast-containing cells that divides the embryo into three equal sectors. Torpedo stage embryos have chloroplast-containing epidermal cells and a central band of chloroplast-containing cells in the cortex layer, just below the shoot apical meristem. In the walking-stick stage of embryogenesis, chloroplasts are present in the epidermal, cortex and endodermal cells. The chloroplasts appear reduced or absent from the provascular and columella cells of walking-stick stage embryos. These results suggest that there is a tight regulation of plastid differentiation during embryogenesis that generates specific patterns of chloroplast-containing cells in specific cell layers at specific stages of embryogenesis.

  17. Self-quenched covalent fluorescent dye-nucleic acid conjugates as polymeric substrates for enzymatic nuclease assays.

    Science.gov (United States)

    Trubetskoy, Vladimir S; Hagstrom, James E; Budker, Vladimir G

    2002-01-01

    A fluorescent method is described for assessing nuclease activity. The technique is based on the preparation of quenched fluorophore-nucleic acid covalent conjugates and their subsequent dequenching due to degradation by nucleases. The resulting fluorescence increase can be measured by a spectrofluorometer and exhibits subpicogram per milliliter sensitivity level for RNase A and low picogram per milliliter level for DNase I. The method is adaptable for quantitative nuclease inhibitor testing.

  18. Quenching of fluorescence by crystal violet and its use to differentiate between surface-bound and internalized bacteria

    Science.gov (United States)

    Mathew, S.; Lim, Y. C.; Kishen, A.

    2008-06-01

    Phagocytosis is a complex process involving attachment, ingestion and intracellular processing of bacteria by phagocytes. A great difficulty in the evaluation of this process is to differentiate between attachment of the particles to the cell surface and internalization of the particles by the cells. Various techniques have been used to differentiate internalized and surface-attached bacteria in cultured cells, but only a few permit differentiations between surface-bound and internalized bacteria. In this study the quenching of fluorescence by crystal violet on acridine orange stained bacterial biofilm and planktonic bacterial cells is used to differentiate between surface-bound and internalized bacteria within macrophages. Method: One week old Enterococcus faecalis biofilm was grown on perspex and glass substrates in All-Culture medium (nutrient-rich condition) and phosphate buffered saline (nutrient-deprived condition). As model systems, human monocytic (THP-1) and histiocytic (U937) cell lines were used. These cell lines were incubated with the biofilm bacteria for 4 hrs in CO II incubator at 37 °C. The cells and bacteria were stained with acridine orange and quenched with crystal violet to distinguish between surface-bound and internalized bacteria. Results: The presence of green-fluorescing internalized bacteria was detected within the macrophages under the planktonic, nutrient-rich and nutrient-deprived biofilm conditions. All infecting bacteria take up acridine orange and fluoresced green, crystal violet quenched the fluorescence of extra-cellular adhering bacteria so that only fluorescent intracellular bacteria would be visible under fluorescent light microscopy.

  19. Measuring Norfloxacin Binding to Trypsin Using a Fluorescence Quenching Assay in an Upper-Division, Integrated Laboratory Course

    Science.gov (United States)

    Hicks, Katherine A.

    2016-01-01

    Fluorescence quenching assays are often used to measure dissociation constants that quantify the binding affinity between small molecules and proteins. In an upper-division undergraduate laboratory course, where students work on projects using a guided inquiry-based approach, a binding titration experiment at physiological pH is performed to…

  20. Fluorescence Aggregation-Caused Quenching versus Aggregation-Induced Emission: A Visual Teaching Technology for Undergraduate Chemistry Students

    Science.gov (United States)

    Ma, Xiaofeng; Sun, Rui; Cheng, Jinghui; Liu, Jiaoyan; Gou, Fei; Xiang, Haifeng; Zhou, Xiangge

    2016-01-01

    A laboratory experiment visually exploring two opposite basic principles of fluorescence of aggregation-caused quenching (ACQ) and aggregation-induced emission (AIE) is demonstrated. The students would prepared two salicylaldehyde-based Schiff bases through a simple one-pot condensation reaction of one equiv of 1,2-diamine with 2 equiv of…

  1. Measuring Norfloxacin Binding to Trypsin Using a Fluorescence Quenching Assay in an Upper-Division, Integrated Laboratory Course

    Science.gov (United States)

    Hicks, Katherine A.

    2016-01-01

    Fluorescence quenching assays are often used to measure dissociation constants that quantify the binding affinity between small molecules and proteins. In an upper-division undergraduate laboratory course, where students work on projects using a guided inquiry-based approach, a binding titration experiment at physiological pH is performed to…

  2. Cellular Activation of the Self-Quenched Fluorescent Reporter Probe in Tumor Microenvironment

    Directory of Open Access Journals (Sweden)

    Alexei A. Bogdanov, Jr.

    2002-01-01

    Full Text Available The effect of intralysosomal proteolysis of near-infrared fluorescent (NIRF self-quenched macromolecular probe (PGC-Cy5.5 has been previously reported and used for tumor imaging. Here we demonstrate that proteolysis can be detected noninvasively in vivo at the cellular level. A codetection of GFP fluorescence (using two-photon excitation and NIRF was performed in tumor-bearing animals injected with PGC-Cy5.5. In vivo microscopy of tumor cells in subdermal tissue layers (up to 160 μm showed a strong Cy5.5 dequenching effect in GFP-negative cells. This observation was corroborated by flow cytometry, sorting, and reverse transcription polymerase chain reaction analysis of tumor-isolated cells. Both GFP-positive (81% total and GFP-negative (19% total populations contained Cy5.5-positive cells. The GFP-negative cells were confirmed to be host mouse cells by the absence of rat cathepsin mRNA signal. The subfraction of GFPnegative cells (2.5-3.0% had seven times higher NIRF intensity than the majority of GFP-positive or GFPnegative cells (372 and 55 AU, respectively. Highly NIRF-positive, FP-negative cells were CD45-and MAC3-positive. Our results indicate that: 1 intracellular proteolysis can be imaged in vivo at the cellular level using cathepsin-sensitive probes; 2 tumor-recruited cells of hematopoetic origin participate most actively in uptake and degradation of long-circulating macromolecular probes.

  3. Quantitative Trait Loci Mapping for Chlorophyll Fluorescence and Associated Traits in Wheat (Triticum aestivum)

    Institute of Scientific and Technical Information of China (English)

    De-Long Yang; Rui-Lian Jing; Xiao-Ping Chang; Wei Li

    2007-01-01

    Parameters of chlorophyll fluorescence kinetics (PCFKs) under drought stress condition are generally used to characterize instincts for dehydration tolerance in wheat (Triticum aestivum L.). Therefore, it is important to map quantitative trait loci (QTLs) for PCFKs in wheat genetic improvement for drought tolerance. A doubled haploid (DH)population with 150 lines, derived from a cross between two common wheat varieties, Hanxuan 10 and Lumai 14,was used to analyze the correlation between PCFKs and chlorophyll content (ChlC) and to map QTLs at the grainfilling stage under conditions of both rainfed (drought stress, DS) and well-watered (WW), respectively. QTLs for these traits were detected by QTLMapper version 1.0 based on the composite interval mapping method of the mixed-linear model. The results showed a very significant positive correlation between Fy, Fm, Fv/Fm and Fv/Fo.The correlation coefficients were generally higher under WW than under DS. Also, there was a significant or a highly significant positive correlation between Fv, Fm, Fv/Fm, Fv/Fo and ChlC. The correlation coefficients were higher in the DS group than the WW group. A total of 14 additive QTLs (nine QTLs detected under DS and five QTLs under WW)and 25 pairs of eplstatic QTLs (15 pairs detected under DS and 10 pairs under WW) for PCFKs were mapped on chromosomes 6A, 7A, 1B, 3B, 4D and 7D. The contributions of additive QTLs for PCFKs to phenotype variation were from 8.40% to 72.72%. Four additive QTLs (two QTLs detected under DS and WW apiece) controlling ChlC were mapped on chromosomes 1A, 5A and 7A. The contributions of these QTLs for ChlC to phenotype variation were from 7.27% to 11.68%. Several QTL clusters were detected on chromosomes 1B, 7A and 7D, but no shared chromosomal regions for them were identified under different water regimes, indicating that these QTLs performed different expression patterns under rainfed and well-watered conditions.

  4. Interpreting seasonal changes in the carbon balance of southern Amazonia using measurements of XCO2 and chlorophyll fluorescence from GOSAT

    OpenAIRE

    Parazoo, Nicholas C.; Bowman, Kevin; Frankenberg, Christian; Lee, Jung-Eun; Fisher, Joshua B.; Worden, John; Jones, Dylan B. A.; Berry, Joseph; Collatz, G James; Baker, Ian T.; Jung, Martin; Liu, Junjie; Osterman, Gregory; O'Dell, Chris; Sparks, Athena

    2013-01-01

    Amazon forests exert a major influence on the global carbon cycle, but quantifying the impact is complicated by diverse landscapes and sparse data. Here we examine seasonal carbon balance in southern Amazonia using new measurements of column-averaged dry air mole fraction of CO_2 (XCO_2) and solar induced chlorophyll fluorescence (SIF) from the Greenhouse Gases Observing Satellite (GOSAT) from July 2009 to December 2010. SIF, which reflects gross primary production (GPP), is used to disentang...

  5. Characteristics of Gas Exchange and Chlorophyll Fluorescence in Different Position Leaves at Booting Stage in Rice Plants

    Institute of Scientific and Technical Information of China (English)

    Mo Yi-wei; JIN Song-heng; WANG Zhong; WANG Pin-mei; QIAN Shan-qin; ZHAO Kai; GU Yun-jie; YANG Yi-qing; YAO Sheng; JIANG De-an

    2004-01-01

    To investigate the senescence of rice leaves at different positions at booting stage, gas exchange and chlorophyll fluorescence properties in leaves at different positions were examined by using six rice materials. The net rates of photosynthesis (Pn),stomatal conductance (gs), transpiration rate (E) and water use efficiency (WUE) decreased significantly with lowering of leaf positions,while intercellular CO2 concentration (Cj) had a little change, indicating that the decrease of photosynthetic rate was not resulted from the decrease of gs. The decrease of SPAD reading which had a close correlation with chlorophyll content was one of apparent reasons resulting in the decease of Pn. Further evidence by chlorophyll fluorescence showed that the photochemical efficiency of PS Ⅱ and its electron transport rate (ETR) decreased substantially with lowering of the leaf positions but the variable-to-maximum fluorescence ratio(Fv/Fm) and efficiency of energy conversion of open PS Ⅱ (Fv'/Fm') remained rather stable, suggesting that primary limitation of Pn was suppression of electron transport of PS Ⅰ, and probably associated with carbon assimilation.

  6. Determination of safranine T in food samples by CTAB sensitised fluorescence quenching method of the derivatives of calix[4]arene.

    Science.gov (United States)

    Wang, Wenjun; Zhu, Xiashi; Yan, Chaoguo

    2013-12-01

    In this paper, the interaction of safranine T (ST) and calix[4]arene (4,10,16,22-tetramethoxylresorcinarene carboxylic acid derivatives (TRCA)) was investigated with fluorescence spectroscopy. The results was shown that the fluorescence intensity of TRCA could be quenched by ST, and the fluorescence quenching (ΔF=FTRCA-FST-TRCA) was sensitised in cetyltrimethyl ammonium bromide (CTAB). Under the optimal conditions, the linear range of calibration curve for the determination of ST was 0.10-4.00 μg/mL. The detection limit and RSD was 0.034 μg/mL, 2.30% (n=3). The quantum yield (Yu) of ST was approximately 2.0 times higher in the presence of CTAB than that in the absence of CTAB. The method has been applied for the determination of ST in food samples with satisfactory results.

  7. Complexation of serum albumins and triton X-100: Quenching of tryptophan fluorescence and analysis of the rotational diffusion of complexes

    Science.gov (United States)

    Vlasova, I. M.; Vlasov, A. A.; Saletskii, A. M.

    2016-07-01

    The polarized and nonpolarized fluorescence of bovine serum albumin and human serum albumin in Triton X-100 solutions is studied at different pH values. Analysis of the constants of fluorescence quenching for BSA and HSA after adding Triton X-100 and the hydrodynamic radii of BSA/HSA-detergent complexes show that the most effective complexation between both serum albumins and Triton X-100 occurs at pH 5.0, which lies near the isoelectric points of the proteins. Complexation between albumin and Triton X-100 affects the fluorescence of the Trp-214 residing in the hydrophobic pockets of both BSA and HSA.

  8. Fluorescence-quenching of a liposomal-encapsulated near-infrared fluorophore as a tool for in vivo optical imaging.

    Science.gov (United States)

    Tansi, Felista L; Rüger, Ronny; Rabenhold, Markus; Steiniger, Frank; Fahr, Alfred; Hilger, Ingrid

    2015-01-05

    Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous number of imaging techniques currently available and the progress in instrumentation, there is still a need for highly sensitive probes that are suitable for in vivo imaging. One typical problem of available preclinical fluorescent probes is their rapid clearance in vivo, which reduces their imaging sensitivity. To circumvent rapid clearance, increase number of dye molecules at the target site, and thereby reduce background autofluorescence, encapsulation of the near-infrared fluorescent dye, DY-676-COOH in liposomes and verification of its potential for in vivo imaging of inflammation was done. DY-676 is known for its ability to self-quench at high concentrations. We first determined the concentration suitable for self-quenching, and then encapsulated this quenching concentration into the aqueous interior of PEGylated liposomes. To substantiate the quenching and activation potential of the liposomes we use a harsh freezing method which leads to damage of liposomal membranes without affecting the encapsulated dye. The liposomes characterized by a high level of fluorescence quenching were termed Lip-Q. We show by experiments with different cell lines that uptake of Lip-Q is predominantly by phagocytosis which in turn enabled the characterization of its potential as a tool for in vivo imaging of inflammation in mice models. Furthermore, we use a zymosan-induced edema model in mice to substantiate the potential of Lip-Q in optical imaging of inflammation in vivo. Considering possible uptake due to inflammation-induced enhanced permeability and retention (EPR) effect, an always-on liposome formulation with low, non-quenched concentration of DY-676-COOH (termed Lip-dQ) and the free DY-676-COOH were compared with Lip-Q in animal trials.

  9. Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

    Science.gov (United States)

    Rabenhold, Markus; Steiniger, Frank; Fahr, Alfred; Hilger, Ingrid

    2015-01-01

    Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous number of imaging techniques currently available and the progress in instrumentation, there is still a need for highly sensitive probes that are suitable for in vivo imaging. One typical problem of available preclinical fluorescent probes is their rapid clearance in vivo, which reduces their imaging sensitivity. To circumvent rapid clearance, increase number of dye molecules at the target site, and thereby reduce background autofluorescence, encapsulation of the near-infrared fluorescent dye, DY-676-COOH in liposomes and verification of its potential for in vivo imaging of inflammation was done. DY-676 is known for its ability to self-quench at high concentrations. We first determined the concentration suitable for self-quenching, and then encapsulated this quenching concentration into the aqueous interior of PEGylated liposomes. To substantiate the quenching and activation potential of the liposomes we use a harsh freezing method which leads to damage of liposomal membranes without affecting the encapsulated dye. The liposomes characterized by a high level of fluorescence quenching were termed Lip-Q. We show by experiments with different cell lines that uptake of Lip-Q is predominantly by phagocytosis which in turn enabled the characterization of its potential as a tool for in vivo imaging of inflammation in mice models. Furthermore, we use a zymosan-induced edema model in mice to substantiate the potential of Lip-Q in optical imaging of inflammation in vivo. Considering possible uptake due to inflammation-induced enhanced permeability and retention (EPR) effect, an always-on liposome formulation with low, non-quenched concentration of DY-676-COOH (termed Lip-dQ) and the free DY-676-COOH were compared with Lip-Q in animal trials. PMID:25591069

  10. Fluorescence quenching studies of γ-butyrolactone binding protein (CprB) from Streptomyces coelicolor A3(2).

    Science.gov (United States)

    Biswas, Anwesha; Swarnkar, Ravi K; Hussain, Bhukya; Sahoo, Suraj K; Pradeepkumar, P I; Patwari, G Naresh; Anand, Ruchi

    2014-08-28

    Quorum sensing is a cell density dependent phenomenon that utilizes small molecule inducers like γ-butyrolactones (GBLs) and their receptor proteins for adaptation to the environment. The cognate GBLs that bind to several of this GBL receptor family of proteins remain elusive. Here, using CprB protein from Streptomyces coelicolor A3(2) as a model system, we devise a method suited for ligand screening that would be applicable to the entire family of GBL receptors. Docking studies were performed to confirm the identity of the ligand binding pocket, and it was ascertained that the common γ-butyrolactone moiety interacts with the conserved tryptophan residue (W127) residing in the ligand binding pocket. The presence of W127 in the cavity was exploited to monitor its fluorescence quenching on the addition of two chemically synthesized GBLs. Analysis of the data with both the native and W185L mutant versions of the protein confirmed that the compounds used as quenchers reside in the ligand binding pocket. Furthermore, fluorescence lifetime and potassium iodide (KI) quenching studies established that the quenching is static in nature and that the tryptophan residue is buried and inaccessible to surface quenchers. Additionally, a combination of concentration dependent fluorescence quenching and dynamic light scattering experiments revealed that the binding properties of the protein are concentration dependent and it was concluded that the most efficient binding of the ligand is evoked by working at the lowest concentration of protein, providing a sufficient signal, where the aggregation effects are negligible.

  11. Consistency Between Sun-Induced Chlorophyll Fluorescence and Gross Primary Production of Vegetation in North America

    Science.gov (United States)

    Zhang, Yao; Xiao, Xiangming; Jin, Cui; Dong, Jinwei; Zhou, Sha; Wagle, Pradeep; Joiner, Joanna; Guanter, Luis; Zhang, Yongguang; Zhang , Geli; Qin, Yuanwei; Wang, Jie; Moore, Berrien, III

    2016-01-01

    Accurate estimation of the gross primary production (GPP) of terrestrial ecosystems is vital for a better understanding of the spatial-temporal patterns of the global carbon cycle. In this study,we estimate GPP in North America (NA) using the satellite-based Vegetation Photosynthesis Model (VPM), MODIS (Moderate Resolution Imaging Spectrometer) images at 8-day temporal and 500 meter spatial resolutions, and NCEP-NARR (National Center for Environmental Prediction-North America Regional Reanalysis) climate data. The simulated GPP (GPP (sub VPM)) agrees well with the flux tower derived GPP (GPPEC) at 39 AmeriFlux sites (155 site-years). The GPP (sub VPM) in 2010 is spatially aggregated to 0.5 by 0.5-degree grid cells and then compared with sun-induced chlorophyll fluorescence (SIF) data from Global Ozone Monitoring Instrument 2 (GOME-2), which is directly related to vegetation photosynthesis. Spatial distribution and seasonal dynamics of GPP (sub VPM) and GOME-2 SIF show good consistency. At the biome scale, GPP (sub VPM) and SIF shows strong linear relationships (R (sup 2) is greater than 0.95) and small variations in regression slopes ((4.60-5.55 grams Carbon per square meter per day) divided by (milliwatts per square meter per nanometer per square radian)). The total annual GPP (sub VPM) in NA in 2010 is approximately 13.53 petagrams Carbon per year, which accounts for approximately 11.0 percent of the global terrestrial GPP and is within the range of annual GPP estimates from six other process-based and data-driven models (11.35-22.23 petagrams Carbon per year). Among the seven models, some models did not capture the spatial pattern of GOME-2 SIF data at annual scale, especially in Midwest cropland region. The results from this study demonstrate the reliable performance of VPM at the continental scale, and the potential of SIF data being used as a benchmark to compare with GPP models.

  12. PhotoSpec - Ground-based Remote Sensing of Solar-Induced Chlorophyll Fluorescence: First Results

    Science.gov (United States)

    Grossmann, K.; Magney, T. S.; Frankenberg, C.; Seibt, U.; Pivovaroff, A. L.; Hurlock, S. C.; Stutz, J.

    2016-12-01

    Solar-Induced Chlorophyll Fluorescence (SIF) emitted from vegetation can be used as a proxy for photosynthetic activity and is observable on a global scale from space. However, many issues on a leaf-to-canopy scale remain poorly understood, such as influences on the SIF signal from environmental conditions, water stress, or radiation. We have developed a novel ground-based spectrometer system for measuring SIF from natural ecosystems. The instrumental set-up, requirements, and measurement technique are based on decades of experience using Differential Optical Absorption Spectroscopy (DOAS), an established method to measure atmospheric trace gases. The instrument consists of three thermally stabilized commercial spectrometers that are linked to a 2D scanning telescope unit via optical fiber bundles, and also includes a commercial photosynthetic active radiation (PAR) sensor. The spectrometers cover a SIF retrieval wavelength range at high spectral resolution (670 - 780 nm, 0.1 nm FWHM), and also provide moderate resolution spectra (400 - 800 nm, 1.5 nm FWHM) to retrieve vegetation indices and the photochemical reflectance index (PRI). We report on results of the first continuous field measurements of this novel system at Stunt Ranch Santa Monica Mountains UC Reserve, where the PhotoSpec instrument was monitoring SIF of four native Californian shrubland species with different adaptations to seasonal summer drought. We report on the correlation with CO2 fluxes over both the growing season and the hot summer period in 2016. We also show detailed measurements of the diurnal cycle of the SIF signal of single broad leaves, as well as dark-light transitions, under controlled experimental conditions. In addition to demonstrating the instrumental set-up, retrieval algorithm, and instrument performance, our results illustrate that SIF measurements at the leaf to ecosystem scale are needed to understand and interpret the SIF signals retrieved at larger scales.

  13. Quality assessment of urban trees using growth visual and chlorophyll fluorescence indicators

    Directory of Open Access Journals (Sweden)

    Uhrin Peter

    2016-06-01

    Full Text Available Urbanised landscape represents composed structures of technical and biotic elements where social and economy activities create living space for human society but with strongly changed environment. To dominant characters belong climate changes with increased air temperature, drought and emission load, which has developed wide spectrum of stress factors influencing the urban vegetation. For the assessment of plant growth and adaptation response, we have used Sycamore maple (Acer pseudoplatanus L. as study model woody plant. In the framework of visual characters, we assessed the following indicators: (a assimilation organs (leaf necrosis; (b crown quality (degree of foliage and degree of dead tree crown; (c trunk and branch quality (mechanical damage, incidence of wood destroying fungus and trunk cavities and callus healing of trunk wounds. Each indicator was assessed in five-point scale, and in the end, the common index of quality was calculated. The quality index achieved 9.33 points in the first and 10.33 in the second evaluation periods in the Nitra city and 2.66 at the both assessed periods in the comparable rural park. In the group of physiological indicators, chlorophyll a fluorescence marker and its Fv/Fm parameter were used. Within three repeating assessment during growing season (June, August and September, the average values reached Fv/Fm = 0.814 in the city and Fv/Fm = 0.829 in rural park. The results confirmed statistical significances between loaded city conditions and relatively clean rural locality. Used markers have shown as appropriate tools for growth response measurements of street trees in a changed urban environment.

  14. Quenching of coumarin emission by CdSe and CdSe/ZnS quantum dots: Implications for fluorescence reporting

    Energy Technology Data Exchange (ETDEWEB)

    Baride, Aravind [Department of Chemistry, University of South Dakota, Vermillion, SD 57069 (United States); Engebretson, Daniel [Biomedical Engineering, University of South Dakota, Vermillion, SD 57069 (United States); Berry, Mary T. [Department of Chemistry, University of South Dakota, Vermillion, SD 57069 (United States); Stanley May, P., E-mail: smay@usd.edu [Department of Chemistry, University of South Dakota, Vermillion, SD 57069 (United States)

    2013-09-15

    The photoinduced release of highly fluorescent 7-diethylamino coumarin (7DEAC) from CdSe quantum dots (QD) modified with a thiocinnamate ligand (11-mercapto undecyl-E-3-(4-(N,N-diethylamino)-2-hydroxy phenyl) propenoate, [4DEATC]) has been previously described. Coumarin fluorescence was used to ‘report’ the photochemical reaction. The current study quantifies the quenching effect of the QDs on the coumarin emission in this system. A systematic study is presented on the quenching of 7DEAC by CdSe and CdSe/ZnS quantum dots capped with 2-[2-(2-methoxyethoxy)ethoxy] ethanethiol (PEG-thiol). A new method for the functionalization of CdSe and CdSe/ZnS QDs with PEG-thiol was developed, which does not require isolation of the as-synthesized QDs. Stern–Volmer analysis was applied to quantify the effect of the PEG-CdSe and PEG-CdSe/ZnS on 7DEAC emission. The Stern–Volmer constant, K{sub SV}, was shown to be inversely proportional to temperature for quenching by PEG-CdSe, and the fluorescence lifetime of 7DEAC was shown to be independent of PEG-CdSe concentration. Room-temperature K{sub SV} values were similar for the PEG-CdSe and PEG-CdSe/ZnS quenchers. The large magnitude of K{sub SV}, the temperature dependence of K{sub SV}, the lifetime data, and the similarity of K{sub SV} values for the core and core–shell QD quenchers are all consistent with a static quenching mechanism. Assuming a static quenching mechanism, the temperature dependence of the coumarin-QD binding constant, K{sub b}, was used to estimate the ΔH and ΔS for the binding process. -- Highlights: • Quenching of a coumarin derivative by CdSe and CdSe/ZnS quantum dots is demonstrated • Stern–Volmer analysis is performed as a function of temperature • Fluorescence lifetime analysis was used to support Stern–Volmer analysis • Data overwhelmingly support quenching via a Static Mechanism • Quenching of coumarin by quantum dots is significant and must be considered in any release and report

  15. The drought impact on satellite solar-induced chlorophyll fluorescence in China during 2007-2015

    Science.gov (United States)

    Li, Ruitao

    2016-04-01

    Drought is one of the most damaging and complicated natural hazards in the world. China is one of the countries which are most severely affected by drought. And there is a severe drought event in China every 2-3 years. From the beginning of the 1980s, some vegetation indices have been used to monitor vegetation under water stress. With the development of remote sensing technology, satellite solar-induced chlorophyll fluorescence (SIF) has emerged as a new method to monitor vegetation in recent years. Some studies have shown that compared with vegetation indices, SIF is more sensitive for vegetation functioning. However, the related studies using the satellite SIF is relatively limited in China. The objective of this study is to investigate the impact of drought on SIF by analyzing the relationships of SIF and crucial land surface parameter under the drought condition and to assess the adaption of satellite SIF in China. The SIF data are from the Global Ozone Monitoring Experiment 2 (GOME-2). Firstly, the widely used Palmer Drought Severity Index (PDSI) was used for drought events identification from 2007 to 2015 in China. On the basis of the identification results, we chose a number of areas of interest according to different land cover types and drought intensity. Then, we analyzed the relationships of SIF and land surface variables, i.e. normalized difference vegetation index (NDVI), the fraction of absorbed photosynthetically active radiation (fPAR), root-zone soil moisture (SMC) and surface skin temperatures (Tskin). The results show that the spatial patterns of negative SIF anomalies are closely relevant to the drought intensity. The decrease of SIF is aggravated in the phase of drought occurs. Moreover we find that the GOME-2 SIF is sensitive to fPAR and fluorescence yield. And the SIF is strongly correlated with SMC, Tskin and NDVI. But the SIF decreases more rapidly during the early time of drought events than NDVI. In other words, the SIF can well capture

  16. An Automated Comparative Observation System for Sun-Induced Chlorophyll Fluorescence of Vegetation Canopies

    Directory of Open Access Journals (Sweden)

    Xijia Zhou

    2016-05-01

    Full Text Available Detecting sun-induced chlorophyll fluorescence (SIF offers a new approach for remote sensing photosynthesis. However, to analyse the response characteristics of SIF under different stress states, a long-term time-series comparative observation of vegetation under different stress states must be carried out at the canopy scale, such that the similarities and differences in SIF change law can be summarized under different time scales. A continuous comparative observation system for vegetation canopy SIF is designed in this study. The system, which is based on a high-resolution spectrometer and an optical multiplexer, can achieve comparative observation of multiple targets. To simultaneously measure the commonly used vegetation index and SIF in the O2-A and O2-B atmospheric absorption bands, the following parameters are used: a spectral range of 475.9 to 862.2 nm, a spectral resolution of approximately 0.9 nm, a spectral sampling interval of approximately 0.4 nm, and the signal-to-noise ratio (SNR can be as high as 1000:1. To obtain data for both the upward radiance of the vegetation canopy and downward irradiance data with a high SNR in relatively short time intervals, the single-step integration time optimization algorithm is proposed. To optimize the extraction accuracy of SIF, the FluorMOD model is used to simulate sets of data according to the spectral resolution, spectral sampling interval and SNR of the spectrometer in this continuous observation system. These data sets are used to determine the best parameters of Fraunhofer Line Depth (FLD, Three FLD (3FLD and the spectral fitting method (SFM, and 3FLD and SFM are confirmed to be suitable for extracting SIF from the spectral measurements. This system has been used to observe the SIF values in O2-A and O2-B absorption bands and some commonly used vegetation index from sweet potato and bare land, the result of which shows: (1 the daily variation trend of SIF value of sweet potato leaves is

  17. An Automated Comparative Observation System for Sun-Induced Chlorophyll Fluorescence of Vegetation Canopies.

    Science.gov (United States)

    Zhou, Xijia; Liu, Zhigang; Xu, Shan; Zhang, Weiwei; Wu, Jun

    2016-05-27

    Detecting sun-induced chlorophyll fluorescence (SIF) offers a new approach for remote sensing photosynthesis. However, to analyse the response characteristics of SIF under different stress states, a long-term time-series comparative observation of vegetation under different stress states must be carried out at the canopy scale, such that the similarities and differences in SIF change law can be summarized under different time scales. A continuous comparative observation system for vegetation canopy SIF is designed in this study. The system, which is based on a high-resolution spectrometer and an optical multiplexer, can achieve comparative observation of multiple targets. To simultaneously measure the commonly used vegetation index and SIF in the O₂-A and O₂-B atmospheric absorption bands, the following parameters are used: a spectral range of 475.9 to 862.2 nm, a spectral resolution of approximately 0.9 nm, a spectral sampling interval of approximately 0.4 nm, and the signal-to-noise ratio (SNR) can be as high as 1000:1. To obtain data for both the upward radiance of the vegetation canopy and downward irradiance data with a high SNR in relatively short time intervals, the single-step integration time optimization algorithm is proposed. To optimize the extraction accuracy of SIF, the FluorMOD model is used to simulate sets of data according to the spectral resolution, spectral sampling interval and SNR of the spectrometer in this continuous observation system. These data sets are used to determine the best parameters of Fraunhofer Line Depth (FLD), Three FLD (3FLD) and the spectral fitting method (SFM), and 3FLD and SFM are confirmed to be suitable for extracting SIF from the spectral measurements. This system has been used to observe the SIF values in O₂-A and O₂-B absorption bands and some commonly used vegetation index from sweet potato and bare land, the result of which shows: (1) the daily variation trend of SIF value of sweet potato leaves is

  18. Spectral reflectance, chlorophyll fluorescence and virological investigations of tobacco plants (Nicotiana tabacum L.) infected with Tobacco mosaic virus (TMV)

    Science.gov (United States)

    Krezhova, Dora; Hristova, Dimitrina; Iliev, Ilko; Yanev, Tony

    Application of multispectral remote sensing techniques to plant condition monitoring has been adopted for various purposes. Remote sensing is a reliable tool for detecting signs of vege-tation stress and diseases. Spectral reflectance and chlorophyll fluorescence are functions of tissue optical properties and biological status of the plants, and illumination conditions. The mean reflectance spectrum depends on the relative composition of all the pigments in the leaf including chlorophylls, carotenoids etc. Chlorophyll fluorescence results from the primary re-actions of photosynthesis and during the last decade it finds widening application as a means for revelation of stress and diseases. The changes in chlorophyll function take place before the alteration in chlorophyll content to occur so that changes in the fluorescence signal arise before any visible signs are apparent. The aim of our investigations was to study the development and spreading out of a viral infection on the leaves of two cultivars tobacco plants (Nicotiana tabacum L.) infected with Tobacco mosaic virus (TMV). We applied two remote sensing tech-niques (spectral reflectance and chlorophyll fluorescence measurements) for evaluation of the changes in the optical properties of the plants in accordance to their physiological status. The serological analyses via the Double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) were made with appropriate kits (Leowe, Germany) for quantitative assessment of the concentration of viruses in the plants. The tobacco plants were grown in green house under controlled conditions. The first cultivar Nevrocop 1146 is known as resistive to the TMV, i.e. it shows hypersensitive response. The second cultivar named Krumovgrad is normally sen-sitive to the TMV. At growth stage 4-6 expanded leaf, up to one leaf from 20 plants for each cultivar were inoculated with TMV. The leaves opposite to the infected ones formed the group of control (untreated) leaves. The

  19. Position-specific incorporation of fluorescent non-natural amino acids into maltose-binding protein for detection of ligand binding by FRET and fluorescence quenching.

    Science.gov (United States)

    Iijima, Issei; Hohsaka, Takahiro

    2009-04-17

    Position-specific incorporation of fluorescent groups is a useful method for analysis of the functions and structures of proteins. We have developed a method for the incorporation of visible-wavelength-fluorescent non-natural amino acids into proteins in a cell-free translation system. Using this technique, we introduced one or two BODIPY-linked amino acids into maltose-binding protein (MBP) to obtain MBP derivatives showing ligand-dependent changes in fluorescence intensity or intensity ratio. BODIPY-FL-aminophenylalanine was incorporated in place of 15 tyrosines, as well as the N-terminal Lys1, and the C-terminal Lys370 of MBP. Fluorescence measurements revealed that MBP containing a BODIPY-FL moiety in place of Tyr210 showed a 13-fold increase in fluorescence upon binding of maltose. Tryptophan-to-phenylalanine substitutions suggest that the increase in fluorescence was the result of a decrease in the quenching of BODIPY-FL by tryptophan located around the binding site. MBP containing a BODIPY-558 moiety also showed a maltose-dependent increase in fluorescence. BODIPY-FL was then additionally incorporated in place of Lys1 of the BODIPY-558-containing MBP as a response to the amber codon. Fluorescence measurements with excitation of BODIPY-FL showed a large change in fluorescence intensity ratio (0.13 to 1.25) upon binding of maltose; this change can be attributed to fluorescence resonance energy transfer (FRET) and maltose-dependent quenching of BODIPY-558. These results demonstrate the usefulness of the position-specific incorporation of fluorescent amino acids in the fluorescence-based detection of protein functions.

  20. A fast and environmental friendly analytical procedure for determination of melamine in milk exploiting fluorescence quenching.

    Science.gov (United States)

    Nascimento, Carina F; Rocha, Diogo L; Rocha, Fábio R P

    2015-02-15

    An environmental friendly procedure was developed for fast melamine determination as an adulterant of protein content in milk. Triton X-114 was used for sample clean-up and as a fluorophore, whose fluorescence was quenched by the analyte. A linear response was observed from 1.0 to 6.0mgL(-1) melamine, described by the Stern-Volmer equation I°/I=(0.999±0.002)+(0.0165±0.004) CMEL (r=0.999). The detection limit was estimated at 0.8mgL(-1) (95% confidence level), which allows detecting as low as 320μg melamine in 100g of milk. Coefficients of variation (n=8) were estimated at 0.4% and 1.4% with and without melamine, respectively. Recoveries to melamine spiked to milk samples from 95% to 101% and similar slopes of calibration graphs obtained with and without milk indicated the absence of matrix effects. Results for different milk samples agreed with those obtained by high performance liquid chromatography at the 95% confidence level.

  1. Remote Sensing of chlorophyll fluorescence and the impact of clouds on the retrival

    Science.gov (United States)

    Köhler, Philipp; Guanter, Luis; Frankenberg, Christian

    2013-04-01

    Remote sensing of sun-induced chlorophyll fluorescence (SIF) is a new, alternative option to gain information about terrestrial photosynthesis and CO2 assimilation on a global scale. The SIF is an electromagnetic signal emitted in the aprox. 650-800 nm spectral window by the photosynthesis apparatus, and can therefore be considered as a direct indicator of plant biochemical processes. The general approach to measure SIF from space is the evaluation of the in-filling of solar Fraunhofer lines or atmospheric absorption bands by SIF. To distinguish the SIF signal from the total incoming radiance at the sensor, which is about 100 times more intense, is a challenge and high resolution measurements are required. The high spectral resolution (approx. 0.02 nm) of the Fourier Transform Spectrometer (FTS) on-board the Greenhouse Gases Observing Satellite (GOSAT) enables such a measurement of SIF by means of the evaluation of the in-filling of solar Fraunhofer lines by SIF. The narrow wavelength band from 755 to 759 nm and around 770 nm can be used for this purpose because they are free from atmospheric absorption features, the solar radiation shows several Fraunhofer lines and the SIF values in this region are relatively high. A new SIF retrieval approach (GARLiC, for GOSAT Retrieval of cholorphyll fluorescence) will be presented in this contribution. This method is intended to simplify some of the assumptions of existing retrieval approaches without a loss in accuracy. The comparison of the GARLiC fluorescence retrievals with two state-of-the-art SIR retrieval methods such as those by Frankenberg et al. (2011) and Guanter et al. (2012) from GOSAT data shows corresponding and feasible results. In addition to the basics of SIF remote sensing, this contribution will assess the effect of clouds in the retrieval. To do this, the SIF retrieval has been coupled to a cloud optical thickness (COT) retrieval algorithm adapted to GOSAT-FTS O2A-band measurements, so that SIF and COT

  2. Latent manganese deficiency in barley can be diagnosed and remediated on the basis of chlorophyll a fluorescence measurements

    DEFF Research Database (Denmark)

    Schmidt, Sidsel Birkelund; Pedas, Pai; Laursen, Kristian Holst;

    2013-01-01

    chlorophyll (Chl) a fluorescence as a tool for diagnosis of latent Mn deficiency. Methods: Barley plants grown under controlled greenhouse conditions or in the field were exposed to different intensities of Mn deficiency. The responses were characterised by analysis of Chl a fluorescence, photosystem II (PSII......) proteins and mineral elements. Results: Analysis of the Chl a fluorescence induction kinetics (FIK) revealed distinct changes long before any visual symptoms of Mn deficiency were apparent. The changes were specific for Mn and did not occur in Mg, S, Fe or Cu deficient plants. The changes in Mn deficient......Background and aims: Manganese (Mn) deficiency represents a major plant nutritional disorder in winter cereals. The deficiency frequently occurs latently and the lack of visual symptoms prevents timely remediation and cause significant yield reductions. These problems prompted us to investigate...

  3. Interactions between polyphenols in thinned young apples and porcine pancreatic α-amylase: Inhibition, detailed kinetics and fluorescence quenching.

    Science.gov (United States)

    Sun, Lijun; Chen, Weiqi; Meng, Yonghong; Yang, Xingbin; Yuan, Li; Guo, Yurong

    2016-10-01

    Young apple polyphenols (YAP) and nine types of phenolic compounds were investigated regarding the inhibitory activity against porcine pancreatic α-amylase (PPA) in vitro. Tannic acid, chlorogenic acid and caffeic acid in YAP showed relatively high inhibition with the IC50 values of 0.30, 1.96 and 3.69mg/mL, respectively. A detailed kinetics of inhibition study revealed that YAP and tannic acid were competitive inhibitors of PPA, whereas chlorogenic acid and caffeic acid were mixed inhibitors, exhibiting both competitive and uncompetitive characteristics. The fluorescence of PPA could be significantly quenched by YAP and the three polyphenols, and their quenching constants were determined. The results showed that for the polyphenols investigated, the order of the apparent static quenching constants (KFQ) was in agreement with that of the reciprocal competitive inhibition constants (1/Kic) (tannic acid>chlorogenic acid>caffeic acid>epicatechin); both of the parameters were contrary to the order of the IC50 values. Thus, combining detailed kinetics and fluorescence quenching studies can be applied to characterise the interactions between polyphenols in young apples and α-amylase.

  4. Capped Fluorescent Carbon Dots for Detection of Hemin: Role of Number of –OH Groups of Capping Agent in Fluorescence Quenching

    Directory of Open Access Journals (Sweden)

    Upama Baruah

    2013-01-01

    Full Text Available We have successfully demonstrated the use of capped carbon dot systems, namely, CDs/β-cd, CDs/LMH, and CDs/Suc, as fluorescent sensors for the detection of hemin. The capped carbon dot systems showed quenching of PL intensity in the presence of hemin. The minimum detection limit was determined to be ~1 μM. The PL response with free Fe(II and Fe(III was also studied. It was observed that PL quenching of capped carbon dot systems in the presence of hemin is dependent on the number of –OH groups in the capping agent. The order of quenching towards hemin was determined to be CDs/β-cd > CDs/LMH = CDs/Suc > CDs. A possible mechanism to account for the observation is also discussed in the paper.

  5. Capped Fluorescent Carbon Dots for Detection of Hemin: Role of Number of –OH Groups of Capping Agent in Fluorescence Quenching

    Science.gov (United States)

    Baruah, Upama; Gogoi, Neelam; Chowdhury, Devasish

    2013-01-01

    We have successfully demonstrated the use of capped carbon dot systems, namely, CDs/β-cd, CDs/LMH, and CDs/Suc, as fluorescent sensors for the detection of hemin. The capped carbon dot systems showed quenching of PL intensity in the presence of hemin. The minimum detection limit was determined to be ~1 μM. The PL response with free Fe(II) and Fe(III) was also studied. It was observed that PL quenching of capped carbon dot systems in the presence of hemin is dependent on the number of –OH groups in the capping agent. The order of quenching towards hemin was determined to be CDs/β-cd > CDs/LMH = CDs/Suc > CDs. A possible mechanism to account for the observation is also discussed in the paper. PMID:24453870

  6. Diurnal and Directional Responses of Chlorophyll Fluorescence and the PRI in a Cornfield

    Science.gov (United States)

    Middleton, Elizabeth; Cheng, Y. B.; Corp, L.; Campbell, P.; Kustas, W.

    2010-01-01

    Determining the health and vigor of vegetation using high spectral resolution remote sensing is an important goal which has application to monitoring agriculture and ecosystem productivity and carbon exchange. Two spectral indices used to assess whether vegetation is performing near-optimally or exhibiting symptoms of environmental stress (e.g., drought or nutrient deficiency, non-optimal temperatures, etc.) are the Photochemical Reflectance Index (PRI) and solar-induced red and far-red Chlorophyll Fluorescence (Fs). Both the PRI and Fs capture the dynamics of photoprotection mechanisms within green foliage: the PRI is based on the association of the reflected radiation in the green spectrum with the xanthophyll cycle, whereas Fs measures the emitted radiation in the red and far-red spectrum. Fs was determined from retrievals in the atmospheric oxygen absorption features centered at 688 and 760 nm using a modified Fraunhofer Line Depth (FLD) method. We previously demonstrated diurnal and seasonal PRI differences for sunlit vs. shaded foliage in a conifer forest canopy, as expressed in the hotspot and darkspot of the Bidirectional Reflectance Function (BRF). In a USDA-ARS experimental field site located in Beltsville, MD, USA, measurements were acquired over a corn crop from a nadir view in 2008 with an ASD FieldSpec Pro (Analytical Spectral Devices, Inc., Boulder, CO, USA) to study the behavior of the PRI for sunlit and shaded foliage as captured in reflectance variations associated with the BRF, in a I m tall canopy in the vegetative growth stage. Those observations were compared to simulations obtained from two radiative transfer models. Measurements were then acquired to examine whether the PRI and Fs were influenced by view zenith and azimuth geometries at different times of day. Those measurements were made in 2010 with the Ocean Optics USB4000 Miniature Fiber Optic Spectrometer (Ocean Optics Inc., Dunedin, Florida, USA) at several times during the day on

  7. Chlorophyll fluorescence protocol for quick detection of triazinone resistant Chenopodium album L.

    Science.gov (United States)

    Mechant, E; De Marez, T; Aper, J; Bulcke, R

    2010-01-01

    Sugar beet growers in Europe are more often confronted with an unsatisfactory control of Chenopodium album L. (fat-hen), possibly due to the presence of a triazinone resistant biotype. So far, two mutations on the psbA-gene, i.e. Ser264-Gly and Ala251-Val, are known to cause resistance in C. album to the photosystem II-inhibiting triazinones metamitron, a key herbicide in sugar beet, and metribuzin. The Ser264-Gly biotype, cross-resistant to many other photosystem II-inhibitors like the triazines atrazine and terbuthylazine, is most common. The second resistant C. album biotype, recorded in Sweden, is highly resistant to triazinones but only slightly cross-resistant to terbuthylazine. Since farmers should adapt their weed control strategy when a resistant biotype is present, a quick and cheap detection method is needed. Therefore, through trial and error, a protocol for detection with chlorophyll fluorescence measurements was developed and put to the test. First, C. album leaves were incubated in herbicide solution (i.e. 0 microM, 25 microM metribuzin, 200 microM metamitron or 25 microM terbuthylazine) during three hours under natural light. After 30 minutes of dark adaptation, photosynthesis yield was measured with Pocket PEA (Hansatech Instruments). In Leaves from sensitive C. album, herbicide treatment reduces photosynthesis yield due to inhibition of photosynthesis at photosystem II. This results in a difference of photosynthesis yield between the untreated control and herbicide treatment. Based on the relative photosynthesis yield (as a percentage of untreated), a classification rule was formulated: C. album is classified as sensitive when its relative photosynthesis yield is less than 90%, otherwise it is resistant. While metribuzin, and to a lesser extent, metamitron treatment allowed a quick detection of triazinone resistant C. album, terbuthylazine treatment was able to distinguish the Ser264-Gly from the Ala251-Val biotype. As a final test, 265 plants

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

    Science.gov (United States)

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

    2010-03-01

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

  9. The chlorophyll a fluorescence induction curve in the green microalga Haematococcus pluvialis: further insight into the nature of the P-S-M fluctuation and its relationship with the "low-wave" phenomenon at steady-state.

    Science.gov (United States)

    Fratamico, Anthony; Tocquin, Pierre; Franck, Fabrice

    2016-06-01

    Chlorophyll fluorescence is an information-rich signal which provides an access to the management of light absorbed by PSII. A good example of this is the succession of fast fluorescence fluctuations during light-induced photosynthetic induction after dark-adaptation. During this period, the fluorescence trace exhibits several inflexion points: O-J-I-P-S-M-T. Whereas the OJIP part of this kinetics has been the subject of many studies, the processes that underly the PSMT transient are less understood. Here, we report an analysis of the PSMT phase in the green microalga Haematococcus pluvialis in terms of electron acceptors and light use by photochemistry, fluorescence and non-photochemical quenching (NPQ). We identify additional sub-phases between P and S delimited by an inflexion point, that we name Q, found in the second time scale. The P-Q phase expresses a transient photochemical quenching specifically due to alternative electron transport to oxygen. During the transition from Q to S, the NPQ increases and then relaxes during the S-M phase in about 1 min. It is suggested that this transient NPQ observed during induction is a high energy state quenching (qE) dependent on the alternative electron transport to molecular oxygen. We further show that this NPQ is of the same nature than the NPQ, known as the low-wave phenomenon, which is transiently observed after a saturating light pulse given at steady-state. In both cases, the NPQ is oxygen-dependent. This NPQ is observed at external pH 6.0, but not at pH 7.5, which seems correlated with faster saturation of the PQ pool at pH 6.0.

  10. Investigation of Leaf Diseases and Estimation of Chlorophyll Concentration in Seven Barley Varieties Using Fluorescence and Hyperspectral Indices

    Directory of Open Access Journals (Sweden)

    Kang Yu

    2013-12-01

    Full Text Available Leaf diseases, such as powdery mildew and leaf rust, frequently infect barley plants and severely affect the economic value of malting barley. Early detection of barley diseases would facilitate the timely application of fungicides. In a field experiment, we investigated the performance of fluorescence and reflectance indices on (1 detecting barley disease risks when no fungicide is applied and (2 estimating leaf chlorophyll concentration (LCC. Leaf fluorescence and canopy reflectance were weekly measured by a portable fluorescence sensor and spectroradiometer, respectively. Results showed that vegetation indices recorded at canopy level performed well for the early detection of slightly-diseased plants. The combined reflectance index, MCARI/TCARI, yielded the best discrimination between healthy and diseased plants across seven barley varieties. The blue to far-red fluorescence ratio (BFRR_UV and OSAVI were the best fluorescence and reflectance indices for estimating LCC, respectively, yielding R2 of 0.72 and 0.79. Partial least squares (PLS and support vector machines (SVM regression models further improved the use of fluorescence signals for the estimation of LCC, yielding R2 of 0.81 and 0.84, respectively. Our results demonstrate that non-destructive spectral measurements are able to detect mild disease symptoms before significant losses in LCC due to diseases under natural conditions.

  11. Temperature dependence of violaxanthin de-epoxidation and non-photochemical fluorescence quenching in intact leaves of Gossypium hirsutum L. and Malva parviflora L.

    Science.gov (United States)

    Bilger, W; Björkman, O

    1991-05-01

    The temperature dependence of the rate of de-epoxidation of violaxanthin to zeaxanthin was determined in leaves of chilling-sensitive Gossypium hirsutum L. (cotton) and chilling-resistant Malva parviflora L. by measurements of the increase in absorbance at 505 nm (ΔA 505) and in the contents of antheraxanthin and zeaxanthin that occur upon exposure of predarkened leaves to excessive light. A linear relationship between ΔA 505 and the decrease in the epoxidation state of the xanthophyll-cycle pigment pool was obtained over the range 10-40° C. The maximal rate of de-epoxidation was strongly temperature dependent; Q10 measured around the temperature at which the leaf had developed was 2.1-2.3 in both species. In field-grown Malva the rate of de-epoxidation at any given measurement temperature was two to three times higher in leaves developed at a relatively low temperature in the early spring than in those developed in summer. Q10 measured around 15° C was in the range 2.2-2.6 in both kinds of Malva leaves, whereas it was as high as 4.6 in cotton leaves developed at a daytime temperature of 30° C. Whereas the maximum (initial) rate of de-epoxidation showed a strong decrease with decreased temperature the degree of de-epoxidation reached in cotton leaves after a 1-2 · h exposure to a constant photon flux density increased with decreased temperature as the rate of photosynthesis decrease. The zeaxanthin content rose from 2 mmol · (mol chlorophyll)(-1) at 30° C to 61 mmol · (mol Chl)(-1) at 10° C, corresponding to a de-epoxidation of 70% of the violaxanthin pool at 10° C. The degree of de-epoxidation at each temperature was clearly related to the amount of excessive light present at that temperature. The relationship between non-photochemical quenching of chlorophyll fluorescence and zeaxanthin formation at different temperatures was determined for both untreated control leaves and for leaves in which zeaxanthin formation was prevented by dithiothreitol

  12. Characterizing the interaction between uranyl ion and fulvic acid using regional integration analysis (RIA) and fluorescence quenching.

    Science.gov (United States)

    Zhu, Bingqi; Ryan, David K

    2016-03-01

    The development of chemometric methods has substantially improved the quantitative usefulness of the fluorescence excitation-emission matrix (EEM) in the analysis of dissolved organic matter (DOM). In this study, Regional Integration Analysis (RIA) was used to quantitatively interpret EEMs and assess fluorescence quenching behavior in order to study the binding between uranyl ion and fulvic acid. Three fulvic acids including soil fulvic acid (SFA), Oyster River fulvic acid (ORFA) and Suwannee River fulvic acid (SRFA) were used and investigated by the spectroscopic techniques. The EEM spectra obtained were divided into five regions according to fluorescence structural features and two distinct peaks were observed in region III and region V. Fluorescence quenching analysis was conducted for these two regions with the stability constants, ligand concentrations and residual fluorescence values calculated using the Ryan-Weber model. Results indicated a relatively strong binding ability between uranyl ion and fulvic acid samples at low pH (log K value varies from 4.11 to 4.67 at pH 3.50). Fluorophores in region III showed a higher binding ability with fewer binding sites than in region V. Stability constants followed the order, SFA > ORFA > SRFA, while ligand concentrations followed the reverse order, SRFA > ORFA > SFA. A comparison between RIA and Parallel Factor Analysis (PARAFAC) data treatment methods was also performed and good agreement between these two methods (less than 4% difference in log K values) demonstrates the reliability of the RIA method in this study.

  13. [Effects of NaCl stress on photosynthesis characteristics and fast chlorophyll fluorescence induction dynamics of Pistacia chinensis leaves].

    Science.gov (United States)

    Li, Xu-Xin; Liu, Bing-Xiang; Guo, Zhi-Tao; Chang, Yue-Xia; He, Lei; Chen, Fang; Lu, Bing-She

    2013-09-01

    By using fast chlorophyll fluorescence induction dynamics analysis technique (JIP-test), this paper studied the photosynthesis characteristics and fast chlorophyll fluorescence induction dynamics of 1-year old Pistacia chinensis seedlings under the stress of NaCl at the concentrations 0% (CK), 0.15%, 0.3%, 0.45%, and 0.6%. With the increasing concentration of NaCl, the contents of Chl a, Chl b, and Chl (a+b) in the seedlings leaves decreased, the Chl a/b ratio decreased after an initial increase, and the carotenoid content increased. The net photosynthetic rate (P(n)) and stomatal conductance (g(s)) decreased gradually with increasing NaCl concentration. The decrease of P(n) was mainly attributed to the stomatal limitation when the NaCl concentration was lower than 0.3%, and to the non-stomatal limitation when the NaCl concentration was higher than 0.3%. The trapped energy flux per RC (TR0/CS0), electron transport flux per RC (ET0/CS0), density of RCs (RC/CS0), and yield or flux ratio (psi(0) or phi(E0)) decreased, but the absorption flux per CS (ABS/CS0) and the K phase (W(k)) and J phase (V) in the O-J-I-P chlorophyll fluorescence induction curves increased distinctly, indicating that NaCl stress damaged the leaf oxygen-evolving complex (OEC), donor sides, and PS II reaction centers. When the NaCl concentration reached 0.3%, the maximum photochemical efficiency (F(v)/F(m)) and performance index (PI(ABS)) decreased 17.7% and 36.6%, respectively, as compared with the control.

  14. Heavy metal stress detection and monitoring via LED-induced chlorophyll fluorescence analysis of Zea mays L. seedlings aimed at polluted soil phytoremediation

    Science.gov (United States)

    Gouveia-Neto, Artur S.; Silva, Elias A., Jr.; da Silva, Airon José; do Nascimento, Clístenes W. A.

    2012-03-01

    Chlorophyll fluorescence spectroscopy is employed to detect and study the time evolution of metal stress of Zea mays L. seedlings aiming polluted soil phytoremediation. The chlorophyll fluorescence spectra of intact leaves are analyzed using 405 nm LED excitation. Red (Fr) and far-red (FFr) emissions around 685 nm and 735 nm, respectively, are examined as a function of the heavy metal concentration. The fluorescence ratio Fr/FFr was employed to monitor the effect of heavy metal upon the physiological state of the plants before signs of visual stress became apparent. The chlorophyll fluorescence analysis permitted detection and evaluation of the damage caused by heavy metal soil contamination in the early stages of the plants growing process, which is not feasible using conventional in vitro spectral analysis.

  15. Non-invasive, whole-plant imaging of chloroplast movement and chlorophyll fluorescence reveals photosynthetic phenotypes independent of chloroplast photorelocation defects in chloroplast division mutants.

    Science.gov (United States)

    Dutta, Siddhartha; Cruz, Jeffrey A; Jiao, Yuhua; Chen, Jin; Kramer, David M; Osteryoung, Katherine W

    2015-10-01

    Leaf chloroplast movement is thought to optimize light capture and to minimize photodamage. To better understand the impact of chloroplast movement on photosynthesis, we developed a technique based on the imaging of reflectance from leaf surfaces that enables continuous, high-sensitivity, non-invasive measurements of chloroplast movement in multiple intact plants under white actinic light. We validated the method by measuring photorelocation responses in Arabidopsis chloroplast division mutants with drastically enlarged chloroplasts, and in phototropin mutants with impaired photorelocation but normal chloroplast morphology, under different light regimes. Additionally, we expanded our platform to permit simultaneous image-based measurements of chlorophyll fluorescence and chloroplast movement. We show that chloroplast division mutants with enlarged, less-mobile chloroplasts exhibit greater photosystem II photodamage than is observed in the wild type, particularly under fluctuating high levels of light. Comparison between division mutants and the severe photorelocation mutant phot1-5 phot2-1 showed that these effects are not entirely attributable to diminished photorelocation responses, as previously hypothesized, implying that altered chloroplast morphology affects other photosynthetic processes. Our dual-imaging platform also allowed us to develop a straightforward approach to correct non-photochemical quenching (NPQ) calculations for interference from chloroplast movement. This correction method should be generally useful when fluorescence and reflectance are measured in the same experiments. The corrected data indicate that the energy-dependent (qE) and photoinhibitory (qI) components of NPQ contribute differentially to the NPQ phenotypes of the chloroplast division and photorelocation mutants. This imaging technology thus provides a platform for analyzing the contributions of chloroplast movement, chloroplast morphology and other phenotypic attributes to the

  16. Effects of nitrogen form on growth,CO2 assimilation,chlorophyll fluorescence,and photosynthetic electron allocation in cucumber and rice plants

    Institute of Scientific and Technical Information of China (English)

    Yan-hong ZHOU; Yi-li ZHANG; Xue-min WANG; Jin-xia CUI; Xiao-jian XIA; Kai SHI; Jing-quan YU

    2011-01-01

    Cucumber and rice plants with varying ammonium(NH4+)sensitivities were used to examine the effects of different nitrogen(N)sources on gas exchange,chlorophyll(ChI)fluorescence quenching,and photosynthetic electron allocation.Compared to nitrate(NO3-)-grown plants,cucumber plants grown under NH4+-nutdtion showed decreased plant growth,net photosynthetic rate,stomatal conductance,intercellular carbon dioxide(CO2)level,transpiration rate,maximum photochemical efficiency of photosystem Ⅱ,and O2-independent alternative electron flux,and increased O2-dependent alternative electron flux.However,the N source had little effect on gas exchange,ChI a fluorescence parameters,and photosynthetic electron allocation in rice plants,except that NH4+-grown plants had a higher O2-independent alternative electron flux than NO3--grown plants.NO3-reduction activity was rarely detected in leaves of NH4+-grown cucumber plants,but was high in NH4+-grown rice plants.These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO3-assimilation,an effect more significant in NO3--grown plants than in NH4+-grown plants.Meanwhile,NH4+-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate(NADPH)for NO3-reduction,regardless of the N form supplied,while NH4+-sensitive plants had a high water-water cycle activity when NH4+was supplied as the sole N source.

  17. Trocas gasosas e fluorescência da clorofila em seis cultivares de cafeeiro sob estresse de alumínio Gas exchange and chlorophyll fluorescence in six coffee cultivars under aluminum stress

    Directory of Open Access Journals (Sweden)

    Maria Luiza Freitas Konrad

    2005-01-01

    Full Text Available Em experimento desenvolvido em casa de vegetação e em câmara de crescimento avaliou-se o efeito do alumínio (Al na fotossíntese de seis cultivares de cafeeiro. As plantas foram cultivadas em solução nutritiva aerada continuamente, contendo duas concentrações de Al, 0 e 0,148 mmol L-1, fornecidas como Al2(SO43. Após 97 dias mediram-se as taxas de assimilação de CO2 (A e transpiração (E, a condutância estomática (gs, a concentração interna de CO2 (Ci, eficiência instantânea de carboxilação (fic e variáveis de fluorescência da clorofila. Em todas as cultivares, a presença de Al causou quedas significantes em A, gs, fic, ocorrendo aumento em Ci. Também se observou aumento significativo na fluorescência basal (Fo e queda na eficiência quântica máxima do fotossistema II (Fv/Fm, sugerindo injúrias na estrutura dos tilacóides causadas pelo Al. Na curva de indução de fotossíntese, observou-se que o Al causou queda no coeficiente de extinção fotoquímica da fluorescência e aumento no coeficiente de extinção não fotoquímico. Os resultados desse estudo indicaram que a queda de A foi devida à queda da condutância estomática, nas atividades bioquímicas e fotoquímicas.Experiments were carried out under greenhouse and growth chamber to evaluate the effects of aluminum (Al on several photosynthetic characteristics in six coffee cultivars. Plants were grown in nutrient solution aerated continuously, containing two Al concentration, 0 and 0.148 mmol L-1, supplied as Al2(SO43. After 97 days of treatament, measurements of CO2 assimilation rate (A, transpiration rate (E, stomatal conductance (gs, internal CO2 concentration (Ci, instantaneous carboxylation efficiency (phic and chlorophyll fluorescence related characteristics were performed. All six cultivars showed decrease in A, gs and phic and increase in Ci. The basal chlorophyll fluorescence yield (Fo increased and the maximum quantum efficiency (Fv/Fm decreased

  18. Fluorescence enhancement and quenching of Eu(TTFA){sub 3} by Ag nanoparticles at different excitations

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qingru, E-mail: wangqingru@lcu.edu.cn [School of Physical Science and Information Technology, LiaochengUniversity, Liaocheng 252059 (China); Shandong Provinical Key Laboratory of Optical Communication Science and Technology, Liaocheng 252059 (China); Shi, Qiang; Li, Shuhong; Wang, Wenjun; Zheng, Shiling [School of Physical Science and Information Technology, LiaochengUniversity, Liaocheng 252059 (China); Shandong Provinical Key Laboratory of Optical Communication Science and Technology, Liaocheng 252059 (China)

    2015-01-15

    The luminescence properties of Eu(TTFA){sub 3} complex in presence of silver nanoparticles were investigated at three excitation wavelengths of 350 nm, 383 nm and 463 nm, respectively. Luminescence quenching and enhancement were both observed at three different excitation and emission wavelengths. Luminescence at 612 nm, 578 nm, 590 nm and 650 nm were enhanced at excitation wavelength of 350 nm, and quenched at excitation wavelength of 383 nm. The enhancement factor reached to 1.6 and the quench factor was about 0.65. For 463 nm excitation, the luminescence at 612 nm was quenched, and the quench factor reached to 0.85. Luminescence at other three emission wavelengths (578 nm, 590 nm, and 650 nm) was enhanced, with the greatest enhancement factor of ∼5. - Highlights: • The luminescence enhancement and quenching were both obtained by using the Ag nanoparticles. • The luminescence enhancement and quenching highly depends on the excitation and emission wavelengths. • The enhancement factor of luminescence also has a great relationship with the intrinsic quantum yield.

  19. Comparison of chlorophyll in the Red Sea derived from MODIS-Aqua and in vivo fluorescence

    KAUST Repository

    Brewin, Robert J W

    2013-09-01

    The Red Sea is a unique marine environment but relatively unexplored. The only available long-term biological dataset at large spatial and temporal scales is remotely-sensed chlorophyll observations (an index of phytoplankton biomass) derived using satellite measurements of ocean colour. Yet such observations have rarely been compared with in situ data in the Red Sea. In this paper, satellite chlorophyll estimates in the Red Sea from the MODIS instrument onboard the Aqua satellite are compared with three recent cruises of in vivo fluorometric chlorophyll measurements taken in October 2008, March 2010 and September to October 2011. The performance of the standard NASA chlorophyll algorithm, and that of a new band-difference algorithm, is found to be comparable with other oligotrophic regions in the global ocean, supporting the use of satellite ocean colour in the Red Sea. However, given the unique environmental conditions of the study area, regional algorithms are likely to fare better and this is demonstrated through a simple adjustment to the band-difference algorithm. © 2013 Elsevier Inc.

  20. Photophysical studies on the interaction of amides with Bovine Serum Albumin (BSA) in aqueous solution: Fluorescence quenching and protein unfolding

    Energy Technology Data Exchange (ETDEWEB)

    Kumaran, R., E-mail: kumaranwau@rediffmail.com [Department of Chemistry, Dwaraka Doss Goverdhan Doss Vaishnav College, Arumbakkam, Chennai 600106 (India); Ramamurthy, P. [National Centre for Ultrafast Processes, University of Madras, Sekhizar Campus, Taramani, Chennai 600113 (India)

    2014-04-15

    Addition. of amides containing a H-CO(NH{sub 2}) or CH{sub 3}-CO(NH{sub 2}) framework to BSA results in a fluorescence quenching. On the contrary, fluorescence enhancement with a shift in the emission maximum towards the blue region is observed on the addition of dimethylformamide (DMF) (H-CON(CH{sub 3}){sub 2}). Fluorescence quenching accompanied initially with a shift towards the blue region and a subsequent red shift in the emission maximum of BSA is observed on the addition of formamide (H-CO(NH{sub 2})), whereas a shift in the emission maximum only towards the red region results on the addition of acetamide (CH{sub 3}-CONH{sub 2}). Steady state emission spectral studies reveal that amides that possess a free NH{sub 2} and N(CH{sub 3}){sub 2} moiety result in fluorescence quenching and enhancement of BSA respectively. The 3D contour spectral studies of BSA with formamide exhibit a shift in the emission towards the red region accompanied with fluorescence quenching, which indicates that the tryptophan residues of the BSA are exposed to a more polar environment. Circular Dichroism (CD) studies of BSA with amides resulted in a gradual decrease in the α-helical content of BSA at 208 nm, which confirms that there is a conformational change in the native structure of BSA. Time-resolved fluorescence studies illustrate that the extent of buried trytophan moieties exposed to the aqueous phase on the addition of amides follows the order DMFfluorescence methods. -- Highlights:

  1. An Integrative Observing and Modeling Approach for the Physiological Understanding of Sun-Induced Chlorophyll Fluorescence in Japan

    Science.gov (United States)

    Kobayashi, H.; Kato, T.; Saitoh, Y.; Noda, H.; Kikosaka, K.; Ichii, K.; Nasahara, K. N.

    2016-12-01

    Satellite-derived sun-induced chlorophyll fluorescence (SIF) is expected to provides a pathway to link leaf level photosynthesis to global GPP. Existing studies have stressed how well the satellite-derived SIF is correlated with the eddy covariance and/or modeled GPPs. There are some challenges in SIF interpretation because the satellite-derived SIF is a mixture of fluorescence emission from sunlit and shaded leaves and multiple scatterings of fluorescence within plant canopies. In this presentation, we show observation and modeling results around Japan and discuss how the integrative observing and modeling approach potentially overcomes the gaps in-between satellite SIF and photosynthesis reaction within leaves. We have analyzed ground-based SIF monitoring systems "Phenological Eye Network (PEN)". PEN covers several eddy flux sites in Japan and is equipped with spectroradiometer (MS-700) since 2003 (at an earliest site). The computed seasonal SIF variations in the different ecosystems show environmental dependency of SIF and GPP. Another ground-based system we are now developing is the vegetation lidar system named LIFS (Laser-Induced Fluorescence Spectrum), which can offer eco-physiological information of plants. LIFS is consisted of a pulsed UV (355 nm) laser, a telescope, a spectrometer/filter, and a gated image-intensified CCD detector. This system has been using to remotely monitor tree growth status, chlorophyll contents in leaves and so on. The physical and physiological theories are necessary for understanding the observed SIF under various environmental conditions. We have been developing leaf to plant canopy scale photosynthesis and SIF models as precise as possible. The developed model has been used to understand how the leaf-level SIF emission can be related to the canopy scale SIF, which enables to investigate the top of canopy SIF observed from ground-based and satellite-derived SIF measurements.

  2. Improvement of Photosynthesis by Sub1 QTL in Rice Under Submergence: Probed by Chlorophyll Fluorescence OJIP Transients

    Directory of Open Access Journals (Sweden)

    Panda Debabrata

    2011-09-01

    Full Text Available The influence of submergence on the photosynthetic activity in rice plants either possessing or not possessing Sub1 QTL i.e. Swarna and Swarna Sub1 cultivars (cv. were evaluated under simulated complete submergence. The leaf photosynthetic rate and stomatal conductance decreased in both the cv. during the progression of submergence as compared to control plant but significant varietal differences was observed after 1 day (d of submergence. Submergence also alters the photo-system (PS II activity, as reflected in a decrease in the values of Fo, Fm and the Fv/Fm ratio and degradation of chlorophyll, more in Swarna than that of Swarna Sub1. Under complete submergence the shape of the OJIP transient also changed in rice leaves with decrease in maximal fluorescence (P=Fm intensity, resulted lowering of variable fluorescence levels. The decrease was more pronounced in Swarna compared to the Swarna Sub1 cv. Thus, Swarna Sub1 improves photosynthetic activity showing more photosynthetic rate compared to Swarna under submergence because, of less degradation of chlorophyll, higher stomatal conductance, and efficient PS II activity.

  3. A Label-Free Microfluidic Biosensor for Activity Detection of Single Microalgae Cells Based on Chlorophyll Fluorescence

    Directory of Open Access Journals (Sweden)

    Junsheng Wang

    2013-11-01

    Full Text Available Detection of living microalgae cells is very important for ballast water treatment and analysis. Chlorophyll fluorescence is an indicator of photosynthetic activity and hence the living status of plant cells. In this paper, we developed a novel microfluidic biosensor system that can quickly and accurately detect the viability of single microalgae cells based on chlorophyll fluorescence. The system is composed of a laser diode as an excitation light source, a photodiode detector, a signal analysis circuit, and a microfluidic chip as a microalgae cell transportation platform. To demonstrate the utility of this system, six different living and dead algae samples (Karenia mikimotoi Hansen, Chlorella vulgaris, Nitzschia closterium, Platymonas subcordiformis, Pyramidomonas delicatula and Dunaliella salina were tested. The developed biosensor can distinguish clearly between the living microalgae cells and the dead microalgae cells. The smallest microalgae cells that can be detected by using this biosensor are 3 μm ones. Even smaller microalgae cells could be detected by increasing the excitation light power. The developed microfluidic biosensor has great potential for in situ ballast water analysis.

  4. Multiple effects of cadmium on the photosynthetic apparatus of Avicennia germinans L. as probed by OJIP chlorophyll fluorescence measurements

    Energy Technology Data Exchange (ETDEWEB)

    Gonzales-Mendoza, D.; Zapata-Perez, O. [Cinvestav Unidad Merida, Yucatan (Mexico). Dept. de Recursos del Mar; Espadas y Gil, F.; Santamaria, J.M. [Unidad de Biotecnologia, CICY, Yucatan (Mexico)

    2007-03-15

    The toxic effects of cadmium on the photosynthetic apparatus of Avicennia germinans were evaluated by means of the chlorophyll fluorescence transient O-J-I-P. The chlorophyll fluorescence transients were recorded in vivo with high time resolution and analyzed according to the OJIP-test that can quantify the performance of photosystem II. Cadmium-treated plants showed a decrease in yield for primary photochemistry, TR{sup 0}/ABS. The performance index of photosystem II (PSII), PI{sub ABS}, decreased due to cadmium treatment. This performance index is the combination of the indexes of three independent parameters: (1) total number of active reaction centers per absorption (RC/ABS), (2) yield of primary photochemistry (TR{sup 0}/ABS), and (3) efficiency with which a trapped exciton can move an electron into the electron transport chain (ET{sup 0}/TR{sup 0}). Additionally, the F{sub 0}/F{sub v} registered the highest sensitivity to the metal, thus indicating that the water-splitting apparatus of the oxidizing side of PSII is the primary site of action of cadmium. In summary, cadmium affects several targets of photosystem II. More specifically the main targets of cadmium, according to the OJIP-test, can be listed as a decrease in the number of active reaction centers and damage to the activity of the water-splitting complex. (orig.)

  5. Chlorophyll Fluorescence in Partially Defoliated Grape Plants (Vitis vinifera L. cv. Chardonnay) / Fluorescencia de la Clorofila en Plantas de Uva (Vitis vinifera L. cv. Chardonnay) Defoliadas Parcialmente

    OpenAIRE

    Peña Olmos Jaime Ernesto; Casierra Posada Fánor

    2013-01-01

    The chlorophyll content and fluorescence weredetermined in five-year-old grape plants (Vitis vinifera L. cv.Chardonnay) that were subjected to early partial defoliation,in Villa de Leyva, Colombia. The experimental design wascompletely randomized, consisting of two treatments (50%defoliation and control), each with four replications of 35 plants. Every two weeks, one of every two recently-emerged leaves was removed from the non-control plants. The determination of total chlorophyll content wa...

  6. THE SYNTHESIS OF Ag-POLYPYRROLE NANOCOMPOSITE COATED LATEX PARTICLES AND THEIR APPLICATION AS A FLUORESCENT QUENCHING AGENT

    Institute of Scientific and Technical Information of China (English)

    Jiang-ru Zhang; Teng Qiu; Hong-fu Yuan; Xiao-yu Li

    2013-01-01

    Submicron-sized Ag-polypyrrole/poly(styrene-co-methacrylic acid) (Ag-PPy/P(St-co-MAA)) composite particles were fabricated via a redox reaction between pyrrole and AgNO3 in the presence of P(St-co-MAA) soap-free latex.The products are characterized by transmission electron microscopy (TEM),electron diffraction spectra (EDS),Raman spectra,thermogravimetric analysis (TGA) and scanning electron microscopy (SEM).The results showed that Ag-PPy nanocomposites were in situ deposited onto the surface of P(St-co-MAA) latex particles tailored by carboxylic-acid groups.The nanocomposites of Ag-PPy distributed on the surface of polymer particles transformed from discretely dots to continuously coating as the reaction temperature increased from 15℃ to 60℃.Strawberry-like composite particles were obtained at the reaction temperature of 60℃.The TGA characterization confirmed that the Ag-PPy nanocomposites loading onto the P(St-co-MAA) particles were systematically controlled over a range of 6 wt%-42 wt% by changing the reaction temperatures.The fluorescence quenching effect of the Ag-PPy/P(St-co-MAA) composite particles was explored on Rhodamine B as a model molecule with the Stern-V(o)1mer quenching constant Ksv of 5.9 × 104 (g/mL)-1.It is suggested that the fluorescence quenching effect is caused by the resonance energy transfer mechanism.

  7. Enzyme-catalyzed Michael addition for the synthesis of warfarin and its determination via fluorescence quenching of L-tryptophan

    Science.gov (United States)

    Yuan, Yusheng; Yang, Liu; Liu, Shaopu; Yang, Jidong; Zhang, Hui; Yan, Jingjing; Hu, Xiaoli

    2017-04-01

    A sensitive fluorescence sensor for warfarin was proposed via quenching the fluorescence of L-tryptophan due to the interaction between warfarin and L-tryptophan. Warfarin, as one of the most effective anticoagulants, was designed and synthesized via lipase from porcine pancreas (PPL) as a biocatalyst to catalyze the Michael addition of 4-hydroxycoumarin to α, β-unsaturated enones in organic medium in the presence of water. Furthermore, the spectrofluorometry was used to detect the concentration of warfarin with a linear range and detection limit (3σ/k) of 0.04-12.0 μmol L- 1 (R2 = 0.994) and 0.01 μmol L- 1, respectively. Herein, this was the first application of bio-catalytic synthesis and fluorescence for the determination of warfarin. The proposed method was applied to determine warfarin of the drug in tablets with satisfactory results.

  8. Fluorescence quenching study of 2,6-bis(5-(4-methylphenyl)-1-H-pyrazol-3-yl)pyridine with metal ions.

    Science.gov (United States)

    Liu, Hua; Li, Fang-Xiong; Pi, Yan; Wang, Dun-Jia; Hu, Yan-Jun; Zheng, Jing

    2015-06-15

    A novel bispyrazole derivative 2,6-bis(5-(4-methylphenyl)-1-H-pyrazol-3-yl)pyridine was synthesized and its structure was confirmed by (1)H NMR, FTIR, MS techniques and elemental analysis. The binding interactions of BMPP with Cd(2+), Co(2+), Pb(2+) and Cu(2+) ions were investigated in MeOH-H2O solution by fluorescence quenching technique at two temperatures (25 and 35°C). Their quenching constants KSV, binding constants K, binding sites n and thermodynamic parameters (ΔH, ΔG and ΔS) were determined. The results indicated that the metal ions quenched the intrinsic fluorescence of the bispyrazole by forming the bispyrazole-metal complexes and their quenching process was a static quenching mechanism. In addition, the process of interaction was spontaneous and mainly ΔS-driven.

  9. Combination of DNA ligase reaction and gold nanoparticle-quenched fluorescent oligonucleotides: a simple and efficient approach for fluorescent assaying of single-nucleotide polymorphisms.

    Science.gov (United States)

    Wang, Hao; Li, Jishan; Wang, Yongxiang; Jin, Jiangyu; Yang, Ronghua; Wang, Kemin; Tan, Weihong

    2010-09-15

    A new fluorescent sensing approach for detection of single-nucleotide polymorphisms (SNPs) is proposed based on the ligase reaction and gold nanoparticle (AuNPs)-quenched fluorescent oligonucleotides. The design exploits the strong fluorescence quenching of AuNPs for organic dyes and the difference in noncovalent interactions of the nanoparticles with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA), where ssDNA can be adsorbed onto the surface of AuNPs while dsDNA cannot be. In the assay, two half primer DNA probes, one being labeled with a dye and the other being phosphorylated, were first incubated with a target DNA template. In the presence of DNA ligase, the two captured ssDNAs are linked for the perfectly matched DNA target to form a stable duplex, but the duplex could not be formed by the single-base mismatched DNA template. After addition of AuNPs, the fluorescence of dye-tagged DNA probe will be efficiently quenched unless the perfectly matched DNA target is present. To demonstrate the feasibility of this design, the performance of SNP detection using two different DNA ligases, T4 DNA ligase and Escherichia coli DNA ligase, were investigated. In the case of T4 DNA ligase, the signal enhancement of the dye-tagged DNA for perfectly matched DNA target is 4.6-fold higher than that for the single-base mismatched DNA. While in the presence of E. coli DNA ligase, the value raises to be 30.2, suggesting excellent capability for SNP discrimination.

  10. Effect of anthocyanins, carotenoids, and flavonols on chlorophyll fluorescence excitation spectra in apple fruit: signature analysis, assessment, modelling, and relevance to photoprotection.

    Science.gov (United States)

    Merzlyak, Mark N; Melø, Thor Bernt; Naqvi, K Razi

    2008-01-01

    Whole apple fruit (Malus domestica Borkh.) widely differing in pigment content and composition has been examined by recording its chlorophyll fluorescence excitation and diffuse reflection spectra in the visible and near UV regions. Spectral bands sensitive to the pigment concentration have been identified, and linear models for non-destructive assessment of anthocyanins, carotenoids, and flavonols via chlorophyll fluorescence measurements are put forward. The adaptation of apple fruit to high light stress involves accumulation of these protective pigments, which absorb solar radiation in broad spectral ranges extending from UV to the green and, in anthocyanin-containing cultivars, to the red regions of the spectrum. In ripening apples the protective effect in the blue region could be attributed to extrathylakoid carotenoids. A simple model, which allows the simulation of chlorophyll fluorescence excitation spectra in the visible range and a quantitative evaluation of competitive absorption by anthocyanins, carotenoids, and flavonols, is described. Evidence is presented to support the view that anthocyanins, carotenoids, and flavonols play, in fruit with low-to-moderate pigment content, the role of internal traps (insofar as they compete with chlorophylls for the absorption of incident light in specific spectral bands), affecting thereby the shape of the chlorophyll fluorescence excitation spectrum.

  11. Responses of chlorophyll fluorescence and nitrogen level of Leymus chinensis Seedling to changes of soil moisture and temperature

    Institute of Scientific and Technical Information of China (English)

    XU Zhen-zhu; ZHOU Guang-sheng; LI Hui

    2004-01-01

    Controlled experiment of Leymus chinensis seedlings grown in the environmental growth chambers at 3 soilmoisture levels and 3 temperature levels was conducted in order to improve the understanding how leafphotosynthetic parameters will respond to climatic change. The results indicated that soil drought and hightemperature decreased the photochemical efficiency of photosystem (Fv/Fm ), the overall photochemical quantumyield of PSIl(yield), the coefficient of photochemical fluorescence quenching(qp), but increased the coefficient ofnon-photochemical fluorescence quenching(qN). Severe soil drought would decrease Fv/Fm and yield by 3.12% and 37.04% under 26℃ condition, respectively, and 6.60% and 73.33% under 32℃ condition, respectively, suggesting that higher temperature may enhance the negative effects of soil drought. All the soil drought treatments resulted in the decline in leaf nitrogen content. There was no significant effect of temperature on leaf nitrogen level, but higher temperature significantly reduced the root nitrogen content and the ratio of root nitrogen to leaf nitrogen, indicating the different strategies of adaptation to soil drought and temperature. It was also implied that higher temperature would enhance the effect of soil drought on leaf photosynthetic capacity, decrease the adaptability of Leymus chinensis to drought.

  12. Fluorescence quenching of boronic acid derivatives by aniline in alcohols – A Negative deviation from Stern–Volmer equation

    Energy Technology Data Exchange (ETDEWEB)

    Geethanjali, H.S. [Department of Physics, Bangalore Institute of Technology, Bangalore 560004, Karnataka (India); Nagaraja, D., E-mail: nagarajdd86@gmail.com [Department of Physics, Bangalore Institute of Technology, Bangalore 560004, Karnataka (India); Melavanki, R.M., E-mail: melavanki73@gmail.com [Department of Physics, M S Ramaiah Institute of Technology, Bangalore 560054, Karnataka (India); Kusanur, R.A. [Department of Chemistry, R.V. College of Engineering, Bangalore 560059, Karnataka (India)

    2015-11-15

    The fluorescence quenching study of two boronic acid derivatives 5-chloro-2-methoxy phenyl boronic acid (5CMPBA) and 4-fluoro-2-methoxyphenyl boronic acid (4FMPBA) in alcohols of varying viscosities is carried out at room temperature by steady state fluorescence measurements. Aniline is used as quencher. The negative deviation in the Stern–Volmer (S–V) plots has been observed for both the molecules with moderate quencher concentration. The downward curvature in the S–V plot is interpreted in terms of existence of different conformers of the solutes in the ground state. The formation of intermolecular and intramolecular hydrogen bonding in alcohol environments is taken to be responsible for the conformational changes in the ground state of the solutes. The modified Stern–Volmer equation or Lehrer equation is used to calculate Stern–Volmer constant (K{sub SV}) and it is found to be above 100 for most of the solvents used. - Highlights: • Fluorescence quenching of two boronic acid derivatives by aniline in alcohols is carried out at room temperature. • A negative deviation is observed in Stern-Volmer(S-V) plots and it is explained using S-V kinetics and Lehrer equation. • The negative deviation observed in the S–V plot is explained in terms of intramolecular and intermolecular hydrogen bond formations.

  13. Employing the fluorescence anisotropy and quenching kinetics of tryptophan to hunt for residual structures in denatured proteins

    Indian Academy of Sciences (India)

    Satish Kumar; Rajaram Swaminathan

    2007-03-01

    Residual structures in denatured proteins have acquired importance in recent years owing to their role as protein-folding initiation sites. Locating these structures in proteins has proved quite formidable, requiring techniques like NMR. Here in this report, we take advantage of the ubiquitous presence of tryptophan residues in residual structures to hunt for their presence using steady-state fluorescence spectroscopy. The surface accessibility and rotational dynamics of tryptophan in putative residual structures among ten different proteins, namely glucagon, melittin, subtilisin carlsberg, myelin basic protein, ribonuclease T1, human serum albumin, barstar mutant, bovine serum albumin, lysozyme and Trp-Met-Asp-Phe-NH2 peptide, was studied using steady state fluorescence quenching and anisotropy, respectively. Five proteins, namely ribonuclease T1, bovine serum albumin, melittin, barstar and hen egg white lysozyme appear likely to possess tryptophan(s) in hydrophobic clusters based on their reduced bimolecular quenching rates and higher steady-state anisotropy in proportion to their chain length. We also show that the fluorescence emission maximum of tryptophan is insensitive to the presence of residual structures.

  14. Homogeneous DNA Detection Based on Fluorescence Quenching by Nanoparticles in Single-step Format :Target-Induced Configuration Transform

    Institute of Scientific and Technical Information of China (English)

    ZHANG,Songbai; WU,Zaisheng; XIE,Ming; SHEN,Guoli; YU,Ruqin

    2009-01-01

    A new strategy for homogeneous detection of DNA hybridization in single-step format was developed based on fluorescence quenching by gold nanoparticles.The gold nanoparticle is functionalized with 5'-thiolated 48-base oligonucleotide(probe sequence),whose 3'-terminus is labeled with fluorescein(FAM),a negatively charged fluo-rescencc dye.The oligonucleotide adopts all extended configuration due to the electrostatic repulsion between nega-tively charged gold nanoparticle and the FAM-attached probe sequence.After addition of the complementary target sequence,specific DNA hybridization induces a conformation change of the probe from an extended stmcture to an arch.1ike configuration,which brings the fluorophore and the gold nanoparticle in close proximity.The fluorescence is efficiently quenched by gold nanoparticles.The fluorescence quenching efficiency is related to the target concen.tration,which allows the quantitative detection for target sequence in a sample.A linear detection range from 1.6 to 209.4 nmoI/L Was obtained under the optimized experimental conditions with a detection limit of 0.1 nmol,L.In the assay system,the gold nanoparticles act as both nanoscaffolds and nanoquenchers.Furthermore,the proposed strategy.in which only two DNA sequences arc involved,is not only different from the traditional molecular bea-cons or reverse molecular beacons but also different from the commonly used sandwich hybridization methods.In addition,the DNA hybridization detection was achieved in homogenous solution in a single-step format,which al-lows real.time detection and quantification with other advantages such as easy operation and elimination of washing steps.

  15. 酪氨酸猝灭Eosin Y的荧光%Fluorescence Quenching of Eosin Y by Tyrosine

    Institute of Scientific and Technical Information of China (English)

    王经东; 李爽; 吕荣; 于安池

    2015-01-01

    氨基酸残基对探针分子的荧光猝灭行为可以为生物大分子的结构及构象动力学研究提供重要的信息。本文运用飞秒瞬态吸收光谱和时间相关单光子计数实验系统研究了在水(H2O)和氘代水(D2O)溶液中乙酰基取代酪氨酸(AcTyr)对Eosin Y的超快荧光猝灭动力学过程。发现导致AcTyr对Eosin Y荧光猝灭的主要原因是由于它们之间形成了短寿命的基态复合物。我们还发现Eosin Y与AcTyr形成的基态复合物的激发态寿命具有明显的动力学同位素效应,表明AcTyr对Eosin Y的荧光猝灭是通过质子耦合电子转移过程发生的。%Quenching of a fluorescent probe by amino acid residues can provide valuable information about the structural and conformational dynamics of a biopolymer. Herein, we systematically investigated the ultrafast fluorescence quenching dynamics of Eosin Y in the presence ofN-acetyl-tyrosine (AcTyr) in H2O and D2O solutions using both femtosecond transient absorption and time-correlated single-photon counting experiments. We found that the quenching of the fluorescence of Eosin Y by AcTyr in aqueous solution is mainly because of the formation of a ground-state complex between Eosin Y and AcTyr. We also found that the lifetime of the ground-state complex formed between Eosin Y and AcTyr showed a clear kinetic isotope effect, indicating that the quenching of the fluorescence of Eosin Y by AcTyr in aqueous solution isvia a proton-coupled electron transfer process.

  16. Effects of sand burial on biomass, chlorophyll fluorescence and extracellular polysaccharides of man-made cyanobacterial crusts under experimental conditions

    Institute of Scientific and Technical Information of China (English)

    WANG WeiBo; YANG CuiYun; TANG DongShan; LI DunHai; LIU YongDing; HU ChunXiang

    2007-01-01

    Soil cyanobacterial crusts occur throughout the world, especially in the semiarid and arid regions. It always encounters sand burial, which is an important feature of mobile sand dunes. A greenhouse study was conducted to determine the effects of sand burial on biomass, chlorophyll fluorescence andextracellular polysaccharides of man-made cyanobacterial crusts in six periods of time (0, 5, 10, 15, 20 and 30 d after burying) and at five depths (0, 0.2, 0.5, 1 and 2cm). The results indicated that with the increase of the burial time and burial depth extracellular polysaccharides content and Fv/Fm decreased correspondingly and there were no significant differences between 20 and 30 burial days under different burial depths. The degradation of chlorophyll a content appeared only at 20 and 30 burial days and there was also no significant difference between them under different burial depths. It was also observed a simultaneous decrease of the values of the Fv/Fm and the content of extracellular polysaccharides happened in the crusted cyanobacterium Microcoleus vaginatus Gom. It may suggest that there exists a relationship between extracellular polysaccharides and recovery of the activity of photosystem Ⅱ (PS Ⅱ) after rehydration.

  17. Quality evaluation of the edible blue-green alga Nostoc flagelliforme using a chlorophyll fluorescence parameter and several biochemical markers.

    Science.gov (United States)

    Gao, Xiang; Yang, Yiwen; Ai, Yufeng; Luo, Hongyi; Qiu, Baosheng

    2014-01-15

    Nostoc flagelliforme is an edible blue-green alga with herbal and dietary values. Due to the diminishing supply of natural N. flagelliforme and the large investment on the development of its cultivation technology, it is anticipated that artificially cultured N. flagelliforme will soon sustain the market supply. Once this change occurs, the storage-associated quality problem will become the focus of attention for future trade. In this paper, we used a chlorophyll fluorescence parameter, maximum quantum efficiency of Photosystem II (Fv/Fm), and several biomarkers to evaluate the quality of several N. flagelliforme samples. It was found that longer storage times resulted in darker coloured solutions (released pigments) and decreased amounts of chlorophyll a (Chl a) and water-soluble sugars (WSS). Additionally, a higher Fv/Fm value suggests better physiological recovery and quality. In actual application, determination of Fv/Fm would be the first step for evaluating the quality of N. flagelliforme, and the biochemical indexes would serve as good secondary markers. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Glyphosate effects on gas exchange and chlorophyll fluorescence responses of two Lolium perenne L. biotypes with differential herbicide sensitivity.

    Science.gov (United States)

    Yanniccari, Marcos; Tambussi, Eduardo; Istilart, Carolina; Castro, Ana María

    2012-08-01

    Despite the extensive use of glyphosate, how it alters the physiology and metabolism of plants is still unclear. Photosynthesis is not regarded to be a primary inhibitory target of glyphosate, but it has been reported to be affected by this herbicide. The aim of the current research was to determine the effects of glyphosate on the light and dark reactions of photosynthesis by comparing glyphosate-susceptible and glyphosate-resistant Lolium perenne biotypes. After glyphosate treatment, accumulation of reduced carbohydrates occurred before a decrease in gas exchange. Stomatal conductance and CO(2) assimilation were reduced earlier than chlorophyll fluorescence and the amount of chlorophyll in susceptible plants. In the glyphosate-resistant biotype, stomatal conductance was the only parameter slightly affected only 5 days post-application. In susceptible plants, the initial glyphosate effects on gas exchange could be a response to a feedback regulation of photosynthesis. Since the herbicide affects actively growing tissues regardless of the inhibition of photosynthesis, the demand of assimilates decreased and consequently induced an accumulation of carbohydrates in leaves. We concluded that stomatal conductance could be a very sensitive parameter to assess both the susceptibility/resistance to glyphosate before the phytotoxic symptoms become evident.

  19. Experimental effects of sand-dust storm on tolerance index, percentage phototoxicity and chlorophyll a fluorescence of Vigna radiata L.

    Directory of Open Access Journals (Sweden)

    M. Alavi

    2015-03-01

    Full Text Available In arid and semi-arid parts of the world excessive mineral aerosol carried by air parcels is a common climatic incident with well-known environmental side effects. In this way, we studied the role of sand-dust accumulation on various aspects of productivity of Vigna radiata L. including dry mass (DM, chlorophyll (Chl a, b, Chlorophyll a fluorescence (effective quantum yield of PSII photochemistry (ФPSII, maximal quantum yield of PSII photochemistry (Fv/Fm and electron transport rate (ETR. V. radiata was exposed to a gradient of dust concentrations in a dust chamber (0.5 (T1, 1(T2 and 1.5 g/m3 (T3 simulated by a dust generator for a period of 60 days. Results of this experiment indicate that DM and Chl content of shoot are negatively correlated with the intensity of the dust exposure. Exposure of V. radiata to dust compared with the control was caused 5% (T1, 14% (T2 and 27% (T3 reduction in leaf DM (p≤0.05, ANOVA. Also, exposure to the dust induced a significant (p≤0.05 reduction in the Total Chl content in (T3 25%. Also, we showed that ФPSII, ETR and Fv/Fm were affected by increasing of the dust concentrations. Exposure to the dust resulted in a significant reduction in ETR of 15%, 22%, and 43%.

  20. The Seasonal Cycle of Satellite Chlorophyll Fluorescence Observations and its Relationship to Vegetation Phenology and Ecosystem Atmosphere Carbon Exchange

    Science.gov (United States)

    Joiner, J.; Yoshida, Y.; Vasilkov, A. P.; Schaefer, K.; Jung, M.; Guanter, L.; Zhang, Y; Garrity, S.; Middleton, E. M.; Huemmrich, K. F.; Gu, L.; Marchesini, L. Belelli

    2014-01-01

    Mapping of terrestrial chlorophyll uorescence from space has shown potentialfor providing global measurements related to gross primary productivity(GPP). In particular, space-based fluorescence may provide information onthe length of the carbon uptake period that can be of use for global carboncycle modeling. Here, we examine the seasonal cycle of photosynthesis asestimated from satellite fluorescence retrievals at wavelengths surroundingthe 740nm emission feature. These retrievals are from the Global OzoneMonitoring Experiment 2 (GOME-2) flying on the MetOp A satellite. Wecompare the fluorescence seasonal cycle with that of GPP as estimated froma diverse set of North American tower gas exchange measurements. Because the GOME-2 has a large ground footprint (40 x 80km2) as compared with that of the flux towers and requires averaging to reduce random errors, we additionally compare with seasonal cycles of upscaled GPP in the satellite averaging area surrounding the tower locations estimated from the Max Planck Institute for Biogeochemistry (MPI-BGC) machine learning algorithm. We also examine the seasonality of absorbed photosynthetically-active radiation(APAR) derived with reflectances from the MODerate-resolution Imaging Spectroradiometer (MODIS). Finally, we examine seasonal cycles of GPP as produced from an ensemble of vegetation models. Several of the data-driven models rely on satellite reflectance-based vegetation parameters to derive estimates of APAR that are used to compute GPP. For forested sites(particularly deciduous broadleaf and mixed forests), the GOME-2 fluorescence captures the spring onset and autumn shutoff of photosynthesis as delineated by the tower-based GPP estimates. In contrast, the reflectance-based indicators and many of the models tend to overestimate the length of the photosynthetically-active period for these and other biomes as has been noted previously in the literature. Satellite fluorescence measurements therefore show potential for

  1. Label-Free MicroRNA Detection Based on Fluorescence Quenching of Gold Nanoparticles with a Competitive Hybridization.

    Science.gov (United States)

    Wang, Wei; Kong, Tao; Zhang, Dong; Zhang, Jinan; Cheng, Guosheng

    2015-11-01

    MicroRNAs (miRNAs), critical biomarkers of acute and chronic diseases, play key regulatory roles in many biological processes. As a result, there is great demand for robust assay platforms to enable an accurate and efficient detection of low-level miRNAs in complex biological samples. In this work, a label-free and Au nanoparticles (NPs) quenching-based competition assay system was developed. In the designed system, Au NPs with diameter sizes of 10 and 20 nm displayed fluorescence quenching efficiencies of 84% and 82% for Cy3 dye on slide surface, whereas the quenching efficiency of commercial BHQ2 quencher was roughly 50%. Assay conditions were optimized for miRNA-205 detection. A limit of detection of 3.8 pM and a detection range covering from 3.8 pM to 10 nM were achieved. Furthermore, the proposed system was capable of specifically discriminating miRNAs with slight variations in their nucleotide sequence and was also qualified for assessing miRNA levels in human serum. Our strategy has the potential to provide new perspectives in profiling the pattern of miRNA expression and biomedical utilizations.

  2. Effect of Light Quality on Photosynthesis and Chlorophyll Fluorescence in Strawberry Leaves

    Institute of Scientific and Technical Information of China (English)

    XU Kai; GUO Yan-ping; ZHANG Shang-long; ZHANG Liang-cheng; ZHANG Ling-xiao

    2004-01-01

    The photosynthetic characteristics of strawberry(Fragaria x ananassa Duch. cv. Toyonoka)leaves under illumination of identical light intensity(55-57% natural light)with different light quality were studied. It was showed that the chlorophyll content,maximal photochemical efficiency of PS Ⅱ(Fv/Fm),Fm/Fo,amount of inactive PS Ⅱ reaction centers(Fi-Fo)and rate of QAreduction were positively correlated with the red-light/blue-light ratios,but the chlorophyll(a/b)ratios were negatively correlated with them. Carotenoid content of the leaves was maximum under the blue film,than under green film,red film,white film and yellow film,and negatively correlated with the red/farred ratios. The apparent quantum yield(AQY),photorespiratory rate(Pr)and carboxylation efficiency(CE)were also strongly affected by light quality. The photosynthetic rate(Pn)in strawberry leaves under green film was significantly lower than under all other film. Our results suggested that light quality is an essential factor regulating the development of PS Ⅱ and phytochrome and an independent blue light photoreceptor,possibly a cryptochrome,can regulate photosynthetic performance.

  3. Role of echinenone in fluorescence quenching in IsiA aggregates from cyanobacteria

    NARCIS (Netherlands)

    D'Haene, S.; Tsoukatos, K.; Lampoura, S.S.; Matthijs, H.C.P.; Dekker, J.P.; Allen, J.F.; Gantt, E.; Goldbeck, J.H.; Osmond, B.

    2008-01-01

    We compare the carotenoid composition and the quenching properties of IsiA aggregates obtained from a Synechocystis PCC 6803 psaFJ-null mutant and from a crtO-null mutant that is unable to synthesize echinenone. Pigment analysis indicates that isolated IsiA aggregates from the psaFJ-null mutant bind

  4. Kinetic analysis of the mechanism and specificity of protein-disulfide isomerase using fluorescence-quenched peptides

    DEFF Research Database (Denmark)

    Westphal, V; Spetzler, J C; Meldal, M

    1998-01-01

    Protein-disulfide isomerase (PDI) is an abundant folding catalyst in the endoplasmic reticulum of eukaryotic cells. PDI introduces disulfide bonds into newly synthesized proteins and catalyzes disulfide bond isomerizations. We have synthesized a library of disulfide-linked fluorescence......-quenched peptides, individually linked to resin beads, for two purposes: 1) to probe PDI specificity, and 2) to identify simple, sensitive peptide substrates of PDI. Using this library, beads that became rapidly fluorescent by reduction by human PDI were selected. Amino acid sequencing of the bead-linked peptides...... revealed substantial similarities. Several of the peptides were synthesized in solution, and a quantitative characterization of pre-steady state kinetics was carried out. Interestingly, a greater than 10-fold difference in affinity toward PDI was seen for various substrates of identical length. As opposed...

  5. Spectral effects of LEDs on chlorophyll fluorescence and pigmentation in Phalaenopsis ‘Vivien’ and ‘Purple Star’

    DEFF Research Database (Denmark)

    Ouzounis, Theoharis; Fretté, Xavier; Ottosen, Carl-Otto

    2015-01-01

    We examined the effect of light emitting diode (LED) lighting in greenhouse facilities on growth, chlorophyll fluorescence and pigmentation in Phalaenopsis 'Vivien' and 'Purple Star' under purpose-built LED arrays yielding c. 200μmolm-2s-1 at plant height for 14h per day and 24/18°Cday....../night temperature, respectively, from January to April 2013. The light treatments were (1) 40% blue in 60% red (40% B/R), (2) 0% blue in 100% red (0% B/R) and (3) white LEDs with 32% blue in white (32% B/W, control), with background daylight under shade screens. The plants were harvested twice for leaf growth...

  6. High Spatio-Temporal-Resolution Detection of Chlorophyll Fluorescence Dynamics from a Single Chloroplast with Confocal Imaging Fluorometer

    CERN Document Server

    Tseng, Yi-Chin

    2016-01-01

    Chlorophyll fluorescence (CF) is a key indicator to study plant physiology or photosynthesis efficiency. Conventionally, CF is characterized by fluorometers, which only allows ensemble measurement through wide-field detection. For imaging fluorometers, the typical spatial and temporal resolutions are on the order of millimeter and second, far from enough to study cellular/sub-cellular CF dynamics. In addition, due to the lack of optical sectioning capability, conventional imaging fluorometers cannot identify CF from a single cell or even a single chloroplast. Here we demonstrated a novel fluorometer based on confocal imaging, that not only provides high contrast images, but also allows CF measurement with spatiotemporal resolution as high as micrometer and millisecond. CF transient (the Kautsky curve) from a single chloroplast is successfully obtained, with both the temporal dynamics and the intensity dependences corresponding well to the ensemble measurement from conventional studies. The significance of con...

  7. Genotypic response of detached leaves versus intact plants for chlorophyll fluorescence parameters under high temperature stress in wheat

    DEFF Research Database (Denmark)

    Sharma, Dew Kumari; Fernández, Juan Olivares; Rosenqvist, Eva;

    2014-01-01

    The genotypic response of wheat cultivars as affected by two methods of heat stress treatment (treatment of intact plants in growth chambers versus treatment of detached leaves in test tubes) in a temperature controlled water bath were compared to investigate how such different methods of heat...... of the cultivar response in intact plants versus detached leaves was low (r=0.13 (with expt.1) and 0.02 with expt.2). The most important difference between the two methods was the pronounced difference in time scale of reaction, which may indicate the involvement of different physiological mechanisms in response...... treatment affect chlorophyll fluorescence parameters. A set of 41 spring wheat cultivars differing in their maximum photochemical efficiency of photosystem (PS) II (Fv/Fm) under heat stress conditions was used. These cultivars were previously evaluated based on the heat treatment of intact plants...

  8. Chlorophyll fluorescence in the evaluation of photosynthetic electron transport chain inhibitors in the pea

    Directory of Open Access Journals (Sweden)

    Marcio Espinosa Farias

    Full Text Available ABSTRACT The study aimed to evaluate the behavior of the chair of photosynthetic electron transport in the presence of DCMU and atrazine in detached leaves of pea through simultaneous measurements of the kinetics of fluorescence transient, fluorescence delayed and modulated reflection at 820 nm. The petioles of the leaves were immersed for two hours in solution of inhibitors at concentrations of 0 (control, 25, 50, 100, 250 and 500 µM. Measurements of the kinetics of fluorescence transient and fluorescence delayed and modulated reflection at 820 nm were recorded simultaneously by the M-PEA fluorometer. Simultaneous measurement of fluorescence transient, fluorescence delayed and modulated 820 nm reflection is important for assessments of the photosynthetic electron transport chain activity tool. The use of specific inhibitors of the electron transport chain allows you to collect and correlate a lot of information about the effect of different inhibitors at specific points in the photosynthetic electron transport chain. DCMU and atrazine are inhibitors of photosystem II and the concentration of 500 mM affects more strongly the flow of photosynthetic electrons.

  9. Effects of electrolysis by low-amperage electric current on the chlorophyll fluorescence characteristics of Microcystis aeruginosa.

    Science.gov (United States)

    Lin, Li; Feng, Cong; Li, Qingyun; Wu, Min; Zhao, Liangyuan

    2015-10-01

    Effects of electrolysis by low-amperage electric current on the chlorophyll fluorescence characteristics of Microcystis aeruginosa were investigated in order to reveal the mechanisms of electrolytic inhibition of algae. Threshold of current density was found under a certain initial no. of algae cell. When current density was equal to or higher than the threshold (fixed electrolysis time), growth of algae was inhibited completely and the algae lost the ability to survive. Effect of algal solution volume on algal inhibition was insignificant. Thresholds of current density were 8, 10, 14, 20, and 22 mA cm(-2) at 2.5 × 10(7), 5 × 10(7), 1 × 10(8), 2.5 × 10(8), and 5 × 10(8) cells mL(-1) initial no. of algae cell, respectively. Correlativity between threshold of current and initial no. of algae cells was established for scale-up and determining operating conditions. Changes of chlorophyll fluorescence parameters demonstrated that photosystem (PS) II of algae was damaged by electrolysis but still maintained relatively high activity when algal solution was treated by current densities lower than the threshold. The activity of algae recovered completely after 6 days of cultivation. On the contrary, when current density was higher than the threshold, connection of phycobilisome (PBS) and PS II core complexes was destroyed, PS II system of algae was damaged irreversibly, and algae could not survive thoroughly. The inactivation of M. aeruginosa by electrolysis can be attributed to irreversible separation of PBS from PS II core complexes and the damage of PS II of M. aeruginosa.

  10. Synthesis, spectral behaviour and photophysics of donor-acceptor kind of chalcones: Excited state intramolecular charge transfer and fluorescence quenching studies

    Science.gov (United States)

    Pannipara, Mehboobali; Asiri, Abdullah M.; Alamry, Khalid A.; Arshad, Muhammad N.; El-Daly, Samy A.

    2015-02-01

    The spectral and photophysical properties of two chalcones containing electron donating and accepting groups with intramolecular charge transfer characteristics were synthesized and characterized by 1H NMR, 13C NMR and X-ray crystallography. Both compounds show very strong solvent polarity dependent changes in their photophysical characteristics, namely, remarkable red shift in the emission spectra with increasing solvent polarity, large change in Stokes shift, significant reduction in the fluorescence quantum yield; indicating that the fluorescence states of these compounds are of intramolecular charge transfer (ICT) character. The solvent effect on the photophysical parameters such as singlet absorption, molar absorptivity, oscillator strength, dipole moment, fluorescence spectra, and fluorescence quantum yield of both compounds have been investigated comprehensively. For both dyes, Lippert-Mataga and Reichardt's correlations were used to estimate the difference between the excited and ground state dipole moments (Δμ). The interactions of dyes with colloidal silver nanoparticles (Ag NPs) were also studied in ethanol using steady state fluorescence quenching measurements. The fluorescence quenching data reveal that dynamic quenching and energy transfer play a major role in the fluorescence quenching of dyes by Ag NPs.

  11. Fast and single-step immunoassay based on fluorescence quenching within a square glass capillary immobilizing graphene oxide-antibody conjugate and fluorescently labelled antibody.

    Science.gov (United States)

    Shirai, Akihiro; Henares, Terence G; Sueyoshi, Kenji; Endo, Tatsuro; Hisamoto, Hideaki

    2016-05-23

    A single-step, easy-to-use, and fast capillary-type immunoassay device composed of a polyethylene glycol (PEG) coating containing two kinds of antibody-reagents, including an antibody-graphene oxide conjugate and fluorescently labelled antibody, was developed in this study. The working principle involved the spontaneous dissolution of the PEG coating, diffusion of reagents, and subsequent immunoreaction, triggered by the capillary action-mediated introduction of a sample solution. In a sample solution containing the target antigen, two types of antibody reagents form a sandwich-type antigen-antibody complex and fluorescence quenching takes place via fluorescence resonance energy transfer between the labelled fluorescent molecules and graphene oxide. Antigen concentration can be measured based on the decrease in fluorescence intensity. An antigen concentration-dependent response was obtained for the model target protein sample (human IgG, 0.2-10 μg mL(-1)). The present method can shorten the reaction time to within 1 min (approximately 40 s), while conventional methods using the same reagents require reaction times of approximately 20 min because of the large reaction scale. The proposed method is one of the fastest immunoassays ever reported. Finally, the present device was used to measure human IgG in diluted serum samples to demonstrate that this method can be used for fast medical diagnosis.

  12. In situ and remote-sensed chlorophyll fluorescence as indicator of the physiological state of phytoplankton near the Isles Kerguelen (Southern Ocean) : Effects of parents, the library, and the school

    NARCIS (Netherlands)

    Timmermans, Klaas R.; Woerd, Hendrik J. van der; Wernand, Marcel R.; Sligting, Merijn; Uitz, Julia; Baar, Hein J.W. de

    Shipboard and remote-sensed Chlorophyll fluorescence were determined in the natural phytoplankton assemblage above the iron-enriched Kerguelen Plateau and the adjacent high-nutrient, low-Chlorophyll open Southern Ocean. The variance between fluorescence yield and photosynthetic efficiency was

  13. Determination of berberine and the study of fluorescence quenching mechanism between berberine and enzyme-catalyzed product

    Science.gov (United States)

    Wang, Huaiyou; Zhang, Miao; Lv, Qingluan; Yue, Ningning; Gong, Bin

    2009-08-01

    A new method for determining berberine has been established based on the principle of fluorescence quenching. The calibration curve was found to be linear between F0/ F and the concentration of berberine with the range of 3.00-20.0 μg mL -1. The detection limit was 0.51 μg mL -1 and the relative standard derivative was 0.18%. Effects of pH, foreign ions and the optimization of variables on the determination of berberine have been examined. The mechanism of the fluorescence quenching has been discussed. The binding constant and the number of binding sites were 1.70 × 10 6 L mol -1 and 1.14, respectively. The data, Δ H = 42.71 kJ mol -1, Δ S = 264.3 J K -1 mol -1 and the mean value Δ G = -39.65 kJ mol -1 were estimated which showed that the reaction was spontaneous and endothermic. The main binding force was hydrophobic force because both Δ H and Δ S were positive.

  14. Probing the adverse temperature dependence in the static fluorescence quenching of BSA induced by a novel anticancer hydrazone.

    Science.gov (United States)

    Tong, Jin-Qiang; Tian, Fang-Fang; Li, Qing; Li, Li-Li; Xiang, Chen; Liu, Yi; Dai, Jie; Jiang, Feng-Lei

    2012-12-01

    A novel hydrazone, 2-hydroxy-N'-(3-hydroxybenzylidene) benzohydrazide (HHB), has been designed, synthesized and characterized. HHB was designed to be an analogue of 311 and PIH with potential anticancer activity, and the IC(50) towards HeLa cell was about 3.46 × 10(-5) mol(-1) L. The interactions of HHB with bovine serum albumin (BSA) had been investigated systematically by spectroscopy, electrochemistry, and molecular modeling under simulative physiological conditions. HHB bound BSA in the sub-domains IIA to form a ground-state complex, inducing the quenching of the intrinsic fluorescence emission, the change of absorption spectrum and the increase of electrical resistance of BSA. An adverse temperature dependence in the fluorescence quenching was detected and discussed to be a reasonable consequence of the big E(a) requirement to overcome the obstructive amino acid residues in the entrance to the binding site, which were closely related to the natural structure of BSA and the molecular shape of HHB. The impact of metal ions, including Fe(2+), Fe(3+), Cu(2+), Mg(2+), Zn(2+), Ca(2+) and Al(3+), towards the interactions of HHB and BSA has been investigated and they were found to affect the HHB-BSA interactions in a mild way.

  15. Non-invasive measurements of leaf epidermal transmittance of UV radiation using chlorophyll fluorescence: field and laboratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, P.W. [Southwest Texas State Univ.. Dept. of Biology, San Marcos, TX (United States); Searles, P.S.; Ryel, R.J.; Caldwell, M.M. [Utah State Univ., Dept. of Rangeland Resources and the Ecology Center, Logan, UT (United States); Ballare, C.L. [IFEVA, Univ. de Buenos Aires, Dept. de Ecologia, Facultad de Agronomia, Buenos Aires, (Argentina)

    2000-07-01

    Ratios of chlorophyll fluorescence induced by ultraviolet (UV) and bluegreen (BG) radiation [F(UV)/F(BG)] were determined with a Xe-PAM fluorometer to test the utility of this technique as a means of non-intrusively assessing changes in the pigmentation and optical properties of leaves exposed to varying UV exposures under laboratory and field conditions. For plants of Vicia faba and Brassica campestris, grown under controlled-environmental conditions, F(UV-B)/F(BG) was negatively correlated with whole-leaf UV-B-absorbing pigment concentrations. Fluorescence ratios of V.faba were similar to, and positively correlated with (r{sup 2} = 0.77 [UV-B]; 0.85 [UV-A]), direct measurements of epidermal transmittance made with an integrating sphere. Leaves of 2 of 4 cultivars of field-grown Glycine max exposed to near-ambient solar UV-B at a mid-latitude site (Buenos Aires, Argentina, 34 degrees S) showed significantly lower abaxial F(UV-B)/F(BG) values (i.e., lower UV-B epidermal transmittance) than those exposed to attenuated UV-B, but solar UV-B reduction had a minimal effect on F(UV-B)/F(BG) in plants growing at a high-latitude site (Tierra del Fuego, Argentina, 55 degrees S). Similarly, the exotic Taraxacum officinale did not show significant changes in F(UV-B)/F(BG) when exposed to very high supplemental UV-B (biologically effective UV-B = 14-15 kJ m{sup -2} day{sup -1}) in the field in Tierra del Fuego, whereas a native species, Gunnera magellanica, showed significant increases in F(UV-B)/F(BG) relative to those receiving ambient UV-B. These anomalous fluorescence changes were associated with increases in BG-absorbing pigments (anthocyanins), but not UV-B-absorbing pigments. These results indicate that non-invasive estimates of epidermal transmittance of UV radiation using chlorophyll fluorescence can detect changes in pigmentation and leaf optical properties induced by UV-B radiation under both field and laboratory conditions. However, this technique may be of limited

  16. Gross Primary Production of a Wheat Canopy Relates Stronger to Far Red Than to Red Solar-Induced Chlorophyll Fluorescence

    Directory of Open Access Journals (Sweden)

    Yves Goulas

    2017-01-01

    Full Text Available Sun-induced chlorophyll fluorescence (SIF is a radiation flux emitted by chlorophyll molecules in the red (RSIF and far red region (FRSIF, and is considered as a potential indicator of the functional state of photosynthesis in remote sensing applications. Recently, ground studies and space observations have demonstrated a strong empirical linear relationship between FRSIF and carbon uptake through photosynthesis (GPP, gross primary production. In this study, we investigated the potential of RSIF and FRSIF to represent the functional status of photosynthesis at canopy level on a wheat crop. RSIF and FRSIF were continuously measured in the O2-B (SIF687 and O2-A bands (SIF760 at a high frequency rate from a nadir view at a height of 21 m, simultaneously with carbon uptake using eddy covariance (EC techniques. The relative fluorescence yield (Fyield and the photochemical yield were acquired at leaf level using active fluorescence measurements. SIF was normalized with photosynthetically active radiation (PAR to derive apparent spectral fluorescence yields (ASFY687, ASFY760. At the diurnal scale, we found limited variations of ASFY687 and ASFY760 during sunny days. We also did not find any link between Fyield and light use efficiency (LUE derived from EC, which would prevent SIF from indicating LUE changes. The coefficient of determination ( r 2 of the linear regression between SIF and GPP is found to be highly variable, depending on the emission wavelength, the time scale of observation, sky conditions, and the phenological stage. Despite its photosystem II (PSII origin, SIF687 correlates less than SIF760 with GPP in any cases. The strongest SIF–GPP relationship was found for SIF760 during canopy growth. When canopy is in a steady state, SIF687 and SIF760 are almost as effective as PAR in predicting GPP. Our results imply some constraints in the use of simple linear relationships to infer GPP from SIF, as they are expected to be better predictive

  17. Analysis of Red and Far-Red Sun-Induced Chlorophyll Fluorescence and Their Ratio in Different Canopies Based on Observed and Modeled Data

    Directory of Open Access Journals (Sweden)

    Micol Rossini

    2016-05-01

    Full Text Available Sun-induced canopy chlorophyll fluorescence in both the red (FR and far-red (FFR regions was estimated across a range of temporal scales and a range of species from different plant functional types using high resolution radiance spectra collected on the ground. Field measurements were collected with a state-of-the-art spectrometer setup and standardized methodology. Results showed that different plant species were characterized by different fluorescence magnitude. In general, the highest fluorescence emissions were measured in crops followed by broadleaf and then needleleaf species. Red fluorescence values were generally lower than those measured in the far-red region due to the reabsorption of FR by photosynthetic pigments within the canopy layers. Canopy chlorophyll fluorescence was related to plant photosynthetic capacity, but also varied according to leaf and canopy characteristics, such as leaf chlorophyll concentration and Leaf Area Index (LAI. Results gathered from field measurements were compared to radiative transfer model simulations with the Soil-Canopy Observation of Photochemistry and Energy fluxes (SCOPE model. Overall, simulation results confirmed a major contribution of leaf chlorophyll concentration and LAI to the fluorescence signal. However, some discrepancies between simulated and experimental data were found in broadleaf species. These discrepancies may be explained by uncertainties in individual species LAI estimation in mixed forests or by the effect of other model parameters and/or model representation errors. This is the first study showing sun-induced fluorescence experimental data on the variations in the two emission regions and providing quantitative information about the absolute magnitude of fluorescence emission from a range of vegetation types.

  18. Linking Physiological Responses, Chlorophyll Fluorescence and Hyperspectral Imagery to Detect Salinity Stress Using the Physiological Reflectance Index in the Coastal Shrub, Myrica cerifera

    Science.gov (United States)

    2008-01-01

    fluorescence prior to any saturating pulse (Fs) was used to estimate the effective quantum yield of photosystem II: ΔF=F Vm ¼ F Vm−Fs½ =F Vm After gas...1989). Photochemical efficiency of photosystem II, photon yield of O2 evolution, photosynthetic capacity, and carotenoid composition during the midday...use efficiency, chlorophyll fluorescence, and reflectance indices associated with ontogenic changes in water- limited Chenopodium quinoa leaves

  19. ‘Golden Delicious’ and ‘Honeycrisp’ apple response to controlled atmosphere storage with oxygen set point determined in response to fruit chlorophyll fluorescence

    Science.gov (United States)

    Postharvest management of apple fruit ripening using controlled atmosphere (CA) cold storage can be enhanced as CA oxygen concentration is decreased to close to the anaerobic compensation point (ACP). Monitoring fruit chlorophyll fluorescence is one technology available to assess fruit response to ...

  20. Response of carbon assimilation and chlorophyll fluorescence to soybean leaf phosphorus across CO2: Alternative electron sink, nutrient efficiency and critical phosphorus concentration

    Science.gov (United States)

    To evaluate the response of CO2 assimilation (PN) and various chlorophyll fluorescence (CF) parameters to phosphorus (P) nutrition soybean plants were grown in controlled environment growth chambers with sufficient (0.50 mM) and deficient (0.10 and 0.01 mM) P supply under ambient and elevated CO2 (a...

  1. 4种苦苣苔科植物光合特性的比较%Comparative study on the photosynthesis and chlorophyll fluorescence of four Gesneriaceae species

    Institute of Scientific and Technical Information of China (English)

    郑月萍; 沈宗根; 姜波; 姜武; 吕洪飞

    2012-01-01

    chlorophyll fluorescence parame-μters of four Gesneriaceae species showed that the quantum yield of PS II linear electron ( Yield) and photochemical quenching coefficient {Qp} decreased as photosynthetic active radiation (PAR) increased from 0 to 1 400 μmol · m-2 · s-1, while the apparent photosynthetic electron transport rate (ETR) and coefficients of non-photochemical fluorescence quenching (qN) had reverse trends. The values of Yield, ETR, qP and qN obtained from the four Gesneriaceae species had the different sequences, i e, D. cortusifolius > C. eburnea > H. henry > B. clarkeana for Yield, ETR and qP, and C. eburnea > H. henryi > D. cortusifolius > B. clarkeana for qN. The chlorophyll fluorescence parameters of four Gesneriaceae species showed that the photosynthetic physiological functions of C. eburnea were better than those of the others, and it would be a suitable candidate used as preference species.rkean for qN.

  2. Study the effect of insecticide dimethoate on photosynthetic pigments and photosynthetic activity of pigeon pea: Laser-induced chlorophyll fluorescence spectroscopy.

    Science.gov (United States)

    Pandey, Jitendra Kumar; Dubey, Gunjan; Gopal, R

    2015-10-01

    Pigeon pea is one of the most important legume crops in India and dimethoate is a widely used insecticide in various crop plants. We studied the effect of dimethoate on growth and photosynthetic activity of pigeon pea plants over a short and long term exposure. Plant growth parameters, photosynthetic pigment content and chlorophyll fluorescence response of pigeon pea (Cajanus cajan L.) plants treated with various concentrations of the insecticide dimethoate (10, 20, 40 and 80 ppm) have been compared for 30 days at regular intervals of 10 days each. Laser induced chlorophyll fluorescence spectra and fluorescence-induction kinetics (FIK) curve of dimethoate treated pigeon pea plants were recorded after 10, 20 and 30 days of treatment. Fluorescence intensity ratio at the two fluorescence maxima (F685/F730) was calculated by evaluating curve-fitted parameters. The variable chlorophyll fluorescence decrease ratio (Rfd) was determined from the FIK curves. Our study revealed that after 10 days of treatment, 10 ppm of dimethoate showed stimulatory response whereas 20, 40 and 80 ppm of dimethoate showed inhibitory response for growth and photosynthetic activity of pigeon pea plants, but after 20 and 30 days of treatment all the tested concentrations of dimethoate became inhibitory. This study clearly shows that dimethoate is highly toxic to the pigeon pea plant, even at very low concentration (10 ppm), if used for a prolonged duration. Our study may thus be helpful in determining the optimal dose of dimethoate in agricultural practices.

  3. Effects of ambient versus reduced UV-B radiation on high arctic Salix arctica assessed by measurements and calculations of chlorophyll-a fluorescence parameters from fluorescence transients

    DEFF Research Database (Denmark)

    Albert, Kristian Rost

    2005-01-01

    cross-section of leaf sample, the number of active PSII reaction centres (RC/ CSM) and electron transport rate (ETM/CSM) and all performance indexes (PIABS, PICSo and PICSm) were increased in reduced UV-B. The total soluble flavonoid content was highest in ambient UV-B. The treatment effects......A UV-B exclusion-experiment was conducted in the high arctic Zackenberg, NE Greenland, in which Salix arctica leaves during most of the growing season were fixed perpendicular to the solar zenith angle, thereby receiving maximal solar radiation. Covered with Teflon and Mylar foil, the leaves...... received approximately 90 and 40% of the ambient UV-B irradiance, respectively. The effects were examined through recordings of chlorophyll a fluorescence transients, determination of biomass and analysis of total carbon and nitrogen content and amount of soluble flavonoids in the leaves. The processing...

  4. Proton equilibration in the chloroplast modulates multiphasic kinetics of nonphotochemical quenching of fluorescence in plants.

    Science.gov (United States)

    Joliot, Pierre A; Finazzi, Giovanni

    2010-07-13

    In plants, the major route for dissipating excess light is the nonphotochemical quenching of absorbed light (NPQ), which is associated with thylakoid lumen acidification. Our data offer an interpretation for the complex relationship between changes in luminal pH and the NPQ response. Upon steady-state illumination, fast NPQ relaxation in the dark reflects the equilibration between the electrochemical proton gradient established in the light and the cellular ATP/ADP+Pi ratio. This is followed by a slower phase, which reflects the decay of the proton motive force at equilibrium, due to gradual cellular ATP consumption. In transient conditions, a sustained lag appears in both quenching onset and relaxation, which is modulated by the size of the antenna complexes of photosystem II and by cyclic electron flow around photosystem I. We propose that this phenomenon reflects the signature of protonation of specific domains in the antenna and of slow H(+) diffusion in the different domains of the chloroplast.

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

    Science.gov (United States)

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

    2013-07-01

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

  6. Chlorophyll fluorescence characteristics of Amaranthus tricolor L.under high temperature stress%高温胁迫下苋菜的叶绿素荧光特性

    Institute of Scientific and Technical Information of China (English)

    陈梅; 唐运来

    2013-01-01

    为了探明高温胁迫对苋菜(Amaranthus tricolor L.)光合过程的影响,用不同温度(25、30、35、40、45℃)处理苋菜植株1h后,随即测定了其叶绿素荧光动力学参数和快速光响应曲线特征参数的变化.结果表明:40℃以上高温胁迫下,苋菜叶片的光系统Ⅱ(PSⅡ)潜在光化学效率(Fv/Fo)、最大光化学效率(Fv/Fm)下降;最大荧光(Fm)、光合电子传递速率(ETR)、PSⅡ实际光化学效率(Yield)、光化学淬灭系数(qP)也均有所下降;而初始荧光(F.)和非光化学淬灭系数(NPQ)在40℃以上高温胁迫下显著上升.叶绿素荧光快速光响应曲线测定结果表明,初始斜率α、最大相对电子传递速率ETRmax和半饱和光强Ik在40℃以上高温胁迫下有所下降.研究表明,40℃以上高温胁迫对苋菜的光能的吸收、转换、光合电子传递和强光耐受能力等均有一定的影响.%Amaranth (Amaranthus tricolor L.) plants were exposed to several temperature levels (25,30,35,40,and 45 ℃) for 1 h,and then,the characteristic parameters of chlorophyll fluorescence and the rapid light response curves of photosynthesis were measured,aimed to understand the effects of high temperature stress on the photosynthesis process of amaranth.High temperature stress (>40 ℃) decreased the maximum fluorescence (Fm),potential photochemical efficiency (Fv/Fo),and maximum photochemical efficiency of PS Ⅱ (Fv/Fm).Simultaneously,the electron transport rate (ETR),actual photochemical efficiency of PS Ⅱ (Yield),and photochemical quenching coefficient (qP) also had some decrease.In contrast,the initial fluorescence (Fo) and non-photochemical quenching coefficient (NPQ) were increased significantly.The initial slope rate (a),maximum apparent electron transport rates (ETRmax),and half-saturation light intensity (Ik) under high temperature stress also had some decline.These results indicated that the photosynthesis of A.tricolor plants was very sensitive to high

  7. Response of Water Stress on Chlorophyll Fluorescence Parameters of Tomato Seedlings%番茄幼苗叶绿素荧光参数对水分胁迫的响应

    Institute of Scientific and Technical Information of China (English)

    须晖; 高洁; 王蕊; 李天来; 马健; 刘满昌

    2011-01-01

    To study the response of tomato seedlings to water stress, the effect on chlorophyll fluorescence properties and chlorophyll content and the relative leaf water content. The results suggested that water stress lead to the maximum quantum efficiency of PSII photochemistry (Fv/Fm), the photochemical quenching (qL)and the linear electron transport rate (ETR) decreased gradually. In contrast, the non photochemical quenching (NPQ) rose gradually. Chlorophyll fluorescence parameters had dash jump phenomena on moderate water stress (the fourth day). Results showed a high correlation (-0.83*) between the decreasing of soil water content (SWC)and NPQ. Hence, NPQ can be an indicator as a guide for irrigation. When NPQ was 2.095, SWC was lower than 32.1%, tomato seedlings were affect on water stress and should be irrigation timely.%以5叶1心期番茄品种‘辽园多丽'为试材,研究番茄幼苗叶绿素荧光特性、叶绿素含量以及叶片相对含水量对水分胁迫的生理响应.结果表明,水分胁迫导致叶绿素荧光参数Fy/Fm、qL、ETR下降,NPQ上升;在轻度水分胁迫下,叶绿素荧光各参数值均有突跃现象.在整个水分胁迫过程中番茄幼苗叶片相对含水量及叶绿素含量均呈下降趋势.NPQ与基质含水量的变化密切相关,相关系数为-0.83',表明荧光参数NPQ可以作为指导灌溉的一个指标.当NPO为2.0975时,基质含水量降到31.2%,番茄幼苗生长受到水分胁迫的影响,应及时灌溉.

  8. Detection of the onset of glyphosate-induced soybean plant injury through chlorophyll fluorescence signal extraction and measurement

    Science.gov (United States)

    Zhao, Feng; Guo, Yiqing; Huang, Yanbo; Reddy, Krishna N.; Zhao, Yanhua; Molin, William T.

    2015-01-01

    In this study, chlorophyll fluorescence (ChlF) was used to detect the onset of soybean plant injury from treatment of glyphosate, the most widely used herbicide. Thirty-six pots of nonglyphosate-resistant soybean were randomly divided into three groups and treated with different doses of glyphosate solutions. The three treatment groups were control (CTRL) group (with no glyphosate treatment), 0.25X group (treated with 0.217 kg.ae/ha solution of glyphosate), and 0.5X group (treated with 0.433 kg.ae/ha solution of glyphosate). Three kinds of fluorescence measurements, steady-state fluorescence spectra, Kautsky effect parameters, and ChlF-related spectral indices were extracted and generated from the measurements in the glyphosate treatment experiment. The mean values of these fluorescence measurements for each of the CTRL group, the 0.25X group, and the 0.5X group were calculated. Glyphosate-induced leaf injury was then analyzed by examining the separability of these mean values at 6, 24, 48, and 72 hours after the treatment (HAT). Results indicate that the peak position of far-red ChlF shows an obvious blue shift for glyphosate-treated soybean, and peak values of steady-state fluorescence spectra for the three groups can be significantly distinguished from each other at 48 HAT and later. Four Kautsky effect parameters, Fv, Fv/Fm, Area, and PI, are parameters sensitive to glyphosate treatment, showing some differences between the CTRL group and treated groups at 24 HAT, and significant differences among the three groups at and beyond 48 HAT. Moreover, ChlF-related spectral indices, R6832/(R675.R690) and R690/R655, are also shown to be useful in detection of the glyphosate injury, though they are less effective than the steady-state fluorescence spectra and the Kautsky effect parameters. Based on the presented results, it can be concluded that glyphosate-induced soybean injury can be detected in a timely manner by the ChlF measurements, and this method has the

  9. Study of plant fluorescence prop erties based on laser-induced chlorophyll fluorescence lifetime imaging technology%基于激光诱导叶绿素荧光寿命成像技术的植物荧光特性研究∗

    Institute of Scientific and Technical Information of China (English)

    万文博; 华灯鑫; 乐静; 闫哲; 周春艳

    2015-01-01

    Plant fluorescence is a susceptible signal in plant fluorescence remote sensing detection. In order to solve this problem, a technique for plant chlorophyll fluorescence lifetime imaging is presented to evaluate living status for plant growth and environmental monitoring. A concave lens is used to expand laser beam at a wavelength of 355 nm, and the living plant is exposed in this laser light source to excite chlorophyll fluorescence. And the chlorophyll fluorescence signals are detected by an intensification charge coupled device. Time resolved measurement method is used in this article, so that every time the same fluorescence signals can be excited by the same laser pulse. Meanwhile, the delay time needed for triggering intensification charge coupled device should be changed consecutively, and the whole discrete fluorescence signal can be obtained. The discrete fluorescence signals from the particular location points of the plant are fitted. An improved method of forward iterative deconvolution is used to retrieve the corresponding fluorescence lifetime, and the high-precision fluorescence lifetime can be obtained. Furthermore, the fluorescence lifetime values at all the location points are retrieved to obtain the distribution map of chlorophyll fluorescence lifetime. This method can give the chlorophyll fluorescence image efficiently. The distribution map of fluorescence lifetime can more effectively reflect the plant chlorophyll concentration than the fluorescence intensity image does. The physical property of chlorophyll fluorescence lifetime from living plants has been studied preliminarily, indicating that the plant physiological status is related to its fluorescence lifetime to a certain extent; and the chlorophyll fluorescence lifetime and plant environment have a subtle and complex correlation. In the future, the relationship between chlorophyll fluorescence lifetime and plant environment will be expected to study with the cooperation of biophysicist.

  10. Fluorescence quenching investigation on the interaction of glutathione-CdTe/CdS quantum dots with sanguinarine and its analytical application.

    Science.gov (United States)

    Shen, Yizhong; Liu, Shaopu; He, Youqiu

    2014-03-01

    Water-soluble glutathione (GSH)-capped core/shell CdTe/CdS quantum dots (QDs) were synthesized. In pH5.4 sodium phosphate buffer medium, the interaction between GSH-CdTe/CdS QDs and sanguinarine (SA) was investigated by spectroscopic methods, including fluorescence spectroscopy and ultraviolet-visible absorption spectroscopy. Addition of SA to GSH-CdTe/CdS QDs results in fluorescence quenching of GSH-CdTe/CdS QDs. Quenching intensity was in proportion to the concentration of SA in a certain range. Investigation of the quenching mechanism, proved that the fluorescence quenching of GSH-CdTe/CdS QDs by SA is a result of electron transfer. Based on the quenching of the fluorescence of GSH-CdTe/CdS QDs by SA, a novel, simple, rapid and specific method for SA determination was proposed. The detection limit for SA was 3.4 ng/mL and the quantitative determination range was 0.2-40.0 µg/mL with a correlation coefficient of 0.9988. The method has been applied to the determination of SA in synthetic samples and fresh urine samples of healthy human with satisfactory results.

  11. Liposomal encapsulation of a near-infrared fluorophore enhances fluorescence quenching and reliable whole body optical imaging upon activation in vivo.

    Science.gov (United States)

    Tansi, Felista L; Rüger, Ronny; Rabenhold, Markus; Steiniger, Frank; Fahr, Alfred; Kaiser, Werner A; Hilger, Ingrid

    2013-11-11

    In the past decade, there has been significant progress in the development of water soluble near-infrared fluorochromes for use in a wide range of imaging applications. Fluorochromes with high photo and thermal stability, sensitivity, adequate pharmacological properties and absorption/emission maxima within the near infrared window (650-900 nm) are highly desired for in vivo imaging, since biological tissues show very low absorption and auto-fluorescence at this spectrum window. Taking these properties into consideration, a myriad of promising near infrared fluorescent probes has been developed recently. However, a hallmark of most of these probes is a rapid clearance in vivo, which hampers their application. It is hypothesized that encapsulation of the near infrared fluorescent dye DY-676-COOH, which undergoes fluorescence quenching at high concentrations, in the aqueous interior of liposomes will result in protection and fluorescence quenching, which upon degradation by phagocytes in vivo will lead to fluorescence activation and enable imaging of inflammation. Liposomes prepared with high concentrations of DY-676-COOH reveal strong fluorescence quenching. It is demonstrated that the non-targeted PEGylated fluorescence-activatable liposomes are taken up predominantly by phagocytosis and degraded in lysosomes. Furthermore, in zymosan-induced edema models in mice, the liposomes are taken up by monocytes and macrophages which migrate to the sites of inflammation. Opposed to free DY-676-COOH, prolonged stability and retention of liposomal-DY-676-COOH is reflected in a significant increase in fluorescence intensity of edema. Thus, protected delivery and fluorescence quenching make the DY-676-COOH-loaded liposomes a highly promising contrast agent for in vivo optical imaging of inflammatory diseases.

  12. Use of O-J-I-P Chlorophyll Fluorescence Transients to Probe Multiple Effects of UV-C Radiation on the Photosynthetic Apparatus of Euglena

    Directory of Open Access Journals (Sweden)

    Chalinda Koshitha Beneragama

    2014-12-01

    Full Text Available Although the kinetic chlorophyll fluorescence signals are rich in information, most of the chlorophyll fluorescence related studies deal only with the quantum yield of primary photochemistry (Fv/Fm. JIP-test based OJIP fluorescence transient analysis is relatively a new technique to investigate the environmental stress responses of photosynthetic organisms. In the present study, the deleterious effects of ultraviolet (UV radiation on the photosynthetic machinery were probed by the JIP-test in Euglena, one of the most potent organisms for the future space stations. The cells were exposed to a series of UV-C doses and immediately after exposure, survival percentage was determined with Neutral Red staining, and the chlorophyll fluorescence was measured using AquaPen AP-C 100 fluorometer. Resultant OJIP transients were analyzed according to JIP-test, and several functional and structural parameters were derived to explain the PSII behavior. Results indicated that the UV-C induced inhibition of electron transport is severely affected due to higher sensitivity of dark reactions after QA -, represented as ψo, the electron transfer probability, than of the light dependent reactions, represented as φPo, the trapping probability. The performance index (PIABS of PSII, which is a combination of the indices of three independent parameters, decreased markedly in exponential manner in response to UVC. Results illustrate the advantage of using a number of fluorescent parameters over the use of one parameter, often the Fv/Fm.

  13. Effects of exogenous spermine on chlorophyll fluorescence, antioxidant system and ultrastructure of chloroplasts in Cucumis sativus L. under salt stress.

    Science.gov (United States)

    Shu, Sheng; Yuan, Ling-Yun; Guo, Shi-Rong; Sun, Jin; Yuan, Ying-Hui

    2013-02-01

    The effects of exogenous spermine (Spm) on plant growth, chlorophyll fluorescence, ultrastructure and anti-oxidative metabolism of chloroplasts were investigated in Cucumis sativus L. under NaCl stress. Salt stress significantly reduced plant growth, chlorophylls content and F(v)/F(m). These changes could be alleviated by foliar spraying with Spm. Salt stress caused an increase in malondialdehyde (MDA) content and superoxide anion [Formula: see text] generation rate in chloroplasts. Application of Spm significantly increased activities of superoxidase dismutase (SOD, EC 1.15.1.1), peroxidase (POD, EC 1.11.1.7), and ascorbate peroxidase (APX, EC 1.11.1.11) which decreased the levels of [Formula: see text] and MDA in the salt-stressed chloroplasts. Salt stress decreased the activities of dehydroascorbate reductase (DHAR, EC 1.8.5.1) and glutathione reductase (GR, EC 1.6.4.2) in the chloroplasts and reduced the contents of dehydroascorbate (DAsA) and glutathione (GSH), but increased monodehydroascorbate reductase (MDAR, EC 1.6.5.4) activity. On the other hand, Spm significantly increased the activities of antioxidant enzymes and levels of antioxidants in the salt-stressed chloroplasts. Further analysis of the ultrastructure of chloroplasts indicated that salinity induced destruction of the chloroplast envelope and increased the number of plastoglobuli with aberrations in thylakoid membranes. However, Spm application to salt-stressed plant leaves counteracted the adverse effects of salinity on the structure of the photosynthetic apparatus. These results suggest that Spm alleviates salt-induced oxidative stress through regulating antioxidant systems in chloroplasts of cucumber seedlings, which is associated with an improvement of the photochemical efficiency of PSII.

  14. Assessment of growth rate, chlorophyll a fluorescence, lipid peroxidation and antioxidant enzyme activity in Aphanizomenon flos-aquae, Pediastrum simplex and Synedra acus exposed to cadmium.

    Science.gov (United States)

    Ran, Xiaofei; Liu, Rui; Xu, Sha; Bai, Fang; Xu, Jinzhu; Yang, Yanjun; Shi, Junqiong; Wu, Zhongxing

    2015-03-01

    In this study, the effects of cadmium on the cyanobacterium Aphanizomenon flos-aquae, the green alga Pediastrum simplex and the diatom Synedra acus was evaluated on the basis of growth rate, chlorophyll a fluorescence, lipid peroxidation and antioxidant enzyme activity. The EC50 values (effective concentration inducing 50 % of growth inhibition) of cadmium in A. flos-aquae, P. simplex and S. acus were 1.18 ± 0.044, 4.32 ± 0.068 and 3.7 ± 0.055 mg/L, respectively. The results suggested that cadmium stress decreases growth rate and chlorophyll a concentration. The normalized chlorophyll a fluorescence transients significantly increased at cadmium concentrations of 5.0, 10.0 and 20.0 mg/L, but slightly decreased at concentrations of 0.2, 0.5 and 1.0 mg/L. The chlorophyll fluorescence parameters showed considerable variation among the three species, while lipid peroxidation and antioxidant enzyme activities showed a significant increase. Our results demonstrated that blockage of electron transport on the acceptor side of photosystem II is the mechanism responsible for cadmium toxicity in freshwater microalgae, and that the tolerance of the three species to cadmium was in the order green alga P. simplex > diatom S. acus > cyanobacterium A. flos-aquae.

  15. Comparing the heterogeneity of copper-binding characteristics for two different-sized soil humic acid fractions using fluorescence quenching combined with 2D-COS.

    Science.gov (United States)

    Hur, Jin; Lee, Bo-Mi

    2011-01-01

    Heterogeneous distributions of copper-binding characteristics were compared for two ultrafiltered size fractions of a soil HA using fluorescence quenching combined with two-dimensional correlation spectroscopy (2D-COS). The apparent shapes of the original synchronous fluorescence spectra and the extent of the fluorescence quenching upon the addition of copper were similar for the two fractions. The stability constants calculated at their highest peaks were not significantly different. However, the 2D-COS results revealed that the fluorescence quenching behaviors were strongly affected by the associated wavelengths and the fraction's size. The spectral change preferentially occurred in the wavelength order of 467 nm → 451 nm → 357 nm for the 1-10 K fraction and of 376 nm → 464 nm for the >100 K fraction. The extent of the binding affinities exactly followed the sequential orders interpreted from the 2D-COS, and they exhibited the distinctive ranges of the logarithmic values from 5.86 to 4.91 and from 6.48 to 5.95 for the 1-10 K and the >100 K fractions, respectively. Our studies demonstrated that fluorescence quenching combined with 2D-COS could be successfully utilized to give insight into the chemical heterogeneity associated with metal-binding sites within the relatively homogeneous HA size fractions.

  16. Photoluminescence of MoS2 quantum dots quenched by hydrogen peroxide: A fluorescent sensor for hydrogen peroxide

    Science.gov (United States)

    Gan, Zhixing; Gui, Qingfeng; Shan, Yun; Pan, Pengfei; Zhang, Ning; Zhang, Lifa

    2016-09-01

    By cutting MoS2 microcrystals to quantum dots (QDs) of sizes below 10 nm, the photoluminescence (PL) at ca. 450 nm can be detected easily due to the quantum confinement effects across the 2D planes. The PL is stable under continuous irradiation of UV light but gradually quenches when treated with an increasing concentration of hydrogen peroxide. Time-resolved PL and Raman spectra imply that H2O2 causes the partial oxidation of MoS2 QDs. First-principles calculations reveal that the MoS2 QDs with oxygen impurity are of indirect bandgap structures showing no notable PL. And absorption spectra verify that the PL of MoS2 QDs quenched by H2O2 is attributed to the oxidation. The integrated PL intensity and H2O2 concentration show an exponential relationship in the range of 2-20 μM, suggesting that MoS2 QDs are potential fluorescent probes for hydrogen peroxide sensing in a physiological environment.

  17. Underwater Optical Fiber Fluorescent System for Measuring Chlorophyll-a Concentration

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Using optical fiber fluorescent technology,a new method for measuring alga concentration in water is presented. The system can realize on-line measurement for alga concentration using He-Ne laser as the light source. It can also effectively detect weak signals. The system with a passive sensor head has such advantages as simple structure, high sensitivity and high accuracy. It has been demonstrated that this system can be used to monitor water quality and can also be used to survey some matter.

  18. 间作遮荫对花生光合作用及叶绿素荧光特性的影响%Effect of Shading on Photosynthesis and Chlorophyll Fluorescence Characteristic of Peanut under Different Inter-row Space in Cassava-peanut Intercropping

    Institute of Scientific and Technical Information of China (English)

    唐秀梅; 唐荣华; 钟瑞春; 揭红科; 刘超; 王泽平; 韩柱强; 蒋菁; 贺梁琼; 李忠

    2011-01-01

    以花生单作为对照,设置30、35、40、45、50 cm 5个木薯花生间作行距,播种90d后测定花生叶片的净光合速率、叶绿素含量及叶绿素荧光参数.结果表明,与单作对照相比,间作花生的光合速率(Pn)、叶绿素含量(Chl a+b)、初始荧光(Fo)、光化学猝灭系数(qP)降低;最大荧光(Fm)、可变荧光(Fv)、最大光化学效率(Fv/ Fm)、潜在光化学活性(Fv/Fo)、非光化学淬灭系数(qN)升高;且窄行距(30~35 cm)处理的Pn、Fv、Fv/Fm、Fv/Fo、表观光合电子传递速率(ETR)、实际光化学量子效率(Yield)高于宽行距(45~50cm)处理.间作遮荫使花生功能叶片的光合速率和叶绿素含量降低,叶绿素荧光参数的一系列变化是花生对间作遮荫的适应性反应.%The net photosynthetic rate, chlorophyll content and chlorophyll fluorescence characteristic of peanut (Arachis hypogaea L. ) were determined under different inter-row space of cassava/peanut intercropping (30, 35, 40, 45, 50 cm) and monocropping in the field after 90 d of sowing. The result showed that the net photosynthetic rate and chlorophyll ( Chi a + b) content, initial fluorescence ( Fo) , photochemical quenching (qP) in leaves of peanut intercropped with cassava decreased. However, the maximum fluorescence (Fm) , variable fluorescence (Fv) , maximum photochemical efficiency (Fv/Fm), potential activity of photosystem II {Fv/Fo, non-photochemical quenching (qN) of intercropped peanut increased. Moreover, Pn, Fv, Fv/Fm , Fv/ Fo, apparent electron transport rates (£77?) and effective quantum yield of photosystem II ( Yield) of peanut intercropped under 30 - 35 cm inter-row treatment were more than those under 40-45 cm row space. In conclusion, the shading of intercropping decreased net photosynthetic rate and chlorophyll content of peanut in leaves, and these changes of chlorophyll fluorescence characteristic showed that peanut had flexibility to shading stress under intercropping.

  19. Preparation of fluorescence quenched libraries containing interchain disulphide bonds for studies of protein disulphide isomerases

    DEFF Research Database (Denmark)

    Spetzler, J C; Westphal, V; Winther, Jakob R.

    1998-01-01

    the chemistry required for the generation of a split-synthesis library, two substrates containing an interchain disulphide bond, a fluorescent probe and a quencher were synthesized. The library consists of a Cys residue flanked by randomized amino acid residues at both sides and the fluorescent Abz group...... at the amino terminal. All the 20 natural amino acids except Cys were employed. The library was linked to PEGA-beads via methionine so that the peptides could be selectively removed from the resin by cleavage with CNBr. A disulphide bridge was formed between the bead-linked library and a peptide containing...

  20. Fabrication of organically modified oxygen sensing film based on fluorescent quenching

    Institute of Scientific and Technical Information of China (English)

    XIN LingLing; XIAO LaiLong; ZHAO Li; CHEN Xi; WANG XiaoRu

    2007-01-01

    An organically modified silicate (ORMOSIL) as a matrix for oxygen-sensitive sensor, in which dimethyldimethoxysilane was selected as an organic modifier in the precursor, is described. The sensing film with tris-(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) as an indicator developed in this paper was characterized by efficient quenching by oxygen. Blue light-emitting diodes ((max = 475 nm) were employed as light excitation source. The linear range of the dissolved oxygen was from 0.5 to 16 (g/mL. The measured RSD was 2%, the response time (t95) was 60 s, and the determination limit was 0.2 (g/mL. A portable and inexpensive luminescence-based sensor was established and applied to the determination of dissolved oxygen in the surface water.

  1. A comparative study of oxygen transmission rates through polymer films based on fluorescence quenching

    DEFF Research Database (Denmark)

    Siró, Istvan; Plackett, David; Sommer-Larsen, Peter

    2010-01-01

    as a potential new instrument for measuring the oxygen permeability of packaging films. The fluorescence-based permeability tester was validated against two existing commercial oxygen permeability measuring devices, the Mocon Ox-Tran 2/20 and PBI-Dansensor OPT-5000. Oxygen transmission rates (OTR) of polylactide...

  2. Effects of manganese stress on growth and chlorophyll fluorescence parameters of Celosia argentea Linn%锰胁迫对青葙生长及叶绿素荧光特性的影响

    Institute of Scientific and Technical Information of China (English)

    尚伟伟; 刘杰; 张学洪; 余轲

    2013-01-01

    Celosia argentea Linn., an annual herb, was found to be a pioneer species on the Mn mine wasteland. To gain fundamental insights into the tolerance of C. argentea to Mn excess, 28-days-old plants grown in aerated nutrient solution were supplied with 2.5(control), 50, 100, 150, 200 and 300 mg·L-1 Mn and analyzed for chlorophyll contents, chlorophyll fluorescence parameters, height and root length. It was found that chlorophyll contents and chlorophyll fluorescence parameters were decreased with increased in Mn supply level. Chlorophyll a, chlorophyll b and total chlorophyll contents dropped significantly as Mn concentrations exceeded 50 mg·L-1; however, the contents of chlorophyll b did not significantly decreased at Mn concentrations ranging from 100 mg·L-1 to 300 mg·L-1 (p>0.05). The responses of chlorophyll fluorescence parameters in leaves of C. argentea showed that maximum quantum yield (Fv/Fm), maximum fluorescence(Fm), minimal fluorescence (Fo), effective quantum yield (EQY), electron transport rate (ETR) and photo chemical quenching (qP) were decreased by Mn stress. The reduction of chlorophyll fluorescence parameters indicated that Mn stress inhibited the electronic transfer process in the plants. At high manganese concentrations (150, 200, 300 mg·L-1), ETR EQY did not vary significantly, although qP decreased progressively with each increase in Mn supply concentration to 300 mg·L-1. Changes in the pattern of plant height were similar to those of ETR and EQY, while C. argentea suffered no significant reduction in root length until the Mn concentration reached 300 mg L-1. The results indicated that C. argentea has a high tolerance to manganese.%通过温室水培实验,研究在不同锰质量浓度(2.5、50、100、150、200、300 mg·L-1)胁迫下青葙(Celosia argentea Linn.)的叶绿素含量、叶绿素荧光参数的变化,及对其生长的影响,探究青葙对锰毒的耐性。结果表明,随着Mn2+质量浓度的升高,青葙叶

  3. New Methods for Retrieval of Chlorophyll Red Fluorescence from Hyperspectral Satellite Instruments: Simulations and Application to GOME-2 and SCIAMACHY

    Science.gov (United States)

    Joiner, Joanna; Yoshida, Yasuko; Guanter, Luis; Middleton, Elizabeth M.

    2016-01-01

    Global satellite measurements of solar-induced fluorescence (SIF) from chlorophyll over land and ocean have proven useful for a number of different applications related to physiology, phenology, and productivity of plants and phytoplankton. Terrestrial chlorophyll fluorescence is emitted throughout the red and far-red spectrum, producing two broad peaks near 683 and 736nm. From ocean surfaces, phytoplankton fluorescence emissions are entirely from the red region (683nm peak). Studies using satellite-derived SIF over land have focused almost exclusively on measurements in the far red (wavelengths greater than 712nm), since those are the most easily obtained with existing instrumentation. Here, we examine new ways to use existing hyperspectral satellite data sets to retrieve red SIF (wavelengths less than 712nm) over both land and ocean. Red SIF is thought to provide complementary information to that from the far red for terrestrial vegetation. The satellite instruments that we use were designed to make atmospheric trace-gas measurements and are therefore not optimal for observing SIF; they have coarse spatial resolution and only moderate spectral resolution (0.5nm). Nevertheless, these instruments, the Global Ozone Monitoring Instrument 2 (GOME-2) and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY), offer a unique opportunity to compare red and far-red terrestrial SIF at regional spatial scales. Terrestrial SIF has been estimated with ground-, aircraft-, or satellite-based instruments by measuring the filling-in of atmospheric andor solar absorption spectral features by SIF. Our approach makes use of the oxygen (O2) gamma band that is not affected by SIF. The SIF-free O2 gamma band helps to estimate absorption within the spectrally variable O2 B band, which is filled in by red SIF. SIF also fills in the spectrally stable solar Fraunhofer lines (SFLs) at wavelengths both inside and just outside the O2 B band, which further helps

  4. Parameter Difference of Chlorophyll Fluorescence in Leaves of Different Cultivars of Lycium barbarum%不同枸杞品种叶绿素荧光参数差异分析

    Institute of Scientific and Technical Information of China (English)

    杨娟; 王有科; 李捷; 陈娜; 李小刚; 张晓娜

    2014-01-01

    In this research,some cultivars of Lycium barbarum were taken as the materials.In the field experiment,the chlorophyll fluorescence parameters and the chlorophyll contents in the cultivars of L.barbarum were studied using the chlorophyll fluorescence measuring technique.The results revealed that the maximal photochemical efficiency of PS Ⅱ (Fv/Fm) and potential activity of PS Ⅱ (Fv/Fo) of Ningqi No.2 were remarkably higher than those of other three cultivars.The actual photosynthesis yield (Y(Ⅱ)),activity photosynthesis yield (Fv'/ Fm'),photochemical quenching (qP) and electron transport rate (ETR) were significantly different from different cultivars under a photo synthetically active radiation of 0-2 847 μmol · m-2 · s-1,and they were the highest in Ningqi No.2,followed by Mengqi No.1 and Damaye,and the lowest in Ningqi No.1.The initial slope α of fitting parameter ETR was similar to the change trend of ETR.The content of Chlorophyll a,Chlorophyll b and Chlorophyll a + b in Ningqi No.2 were the highest.There was an extremely significant or a significant positive correlation between chlorophyll a + b and Y(Ⅱ),Fv'/Fm',qP and ETR,but a negative correlation with NPQ.So it could be concluded that Ningqi No.2 had a higher physiological activity of PS Ⅱ and physiological basis of potential biomass,the photosynthesis capability of all the four cultivars was strong.The photochemical efficiency of Ningqi No.1 was weaker,and it was easy to suffer from photo inhibition at high light intensity.%在田间试验条件下,以宁杞1号、宁杞2号、大麻叶和蒙杞l号为材料,采用叶绿素荧光技术测定了不同枸杞品种的叶绿素荧光参数,并测定供试品种的叶绿素含量.结果表明:宁杞2号的PSⅡ最大光化学效率(Fv/Fm)和PSⅡ潜在活性(Fv/Fo)值显著高于其他3个品种.在不同光照强度(PAR,0~2 847 μmol·m-2·s-1)下,实际光合量子产量[Y(Ⅱ)]、有效光合量子产量(Fv'/Fm')、光化学淬灭系数(qP)

  5. High-Throughput Growth Prediction for Lactuca sativa L. Seedlings Using Chlorophyll Fluorescence in a Plant Factory with Artificial Lighting.

    Science.gov (United States)

    Moriyuki, Shogo; Fukuda, Hirokazu

    2016-01-01

    Poorly grown plants that result from differences in individuals lead to large profit losses for plant factories that use large electric power sources for cultivation. Thus, identifying and culling the low-grade plants at an early stage, using so-called seedlings diagnosis technology, plays an important role in avoiding large losses in plant factories. In this study, we developed a high-throughput diagnosis system using the measurement of chlorophyll fluorescence (CF) in a commercial large-scale plant factory, which produces about 5000 lettuce plants every day. At an early stage (6 days after sowing), a CF image of 7200 seedlings was captured every 4 h on the final greening day by a high-sensitivity CCD camera and an automatic transferring machine, and biological indices were extracted. Using machine learning, plant growth can be predicted with a high degree of accuracy based on biological indices including leaf size, amount of CF, and circadian rhythms in CF. Growth prediction was improved by addition of temporal information on CF. The present data also provide new insights into the relationships between growth and temporal information regulated by the inherent biological clock.

  6. Evaluation of Chlorophyll Fluorescence and Biochemical Traits of Lettuce under Drought Stress and Super Absorbent or Bentonite Application

    Directory of Open Access Journals (Sweden)

    Akram Valizadeh Ghale Beig

    2014-03-01

    Full Text Available The effects of two superabsorbents (natural-bentonite and (synthetic-A 200 on the chlorophyll fluorescence index, proline accumulation, phenolic compounds, antioxidant activity and total carbohydrate in lettuce (Lactuca sativa L. was evaluated. For this purpose, a factorial experiment using completely randomized design with superabsorbents at 3 levels (0, 0.15, 0.30 w/w%, drought stress at 2 levels (60 and 100% of field capacity and 4 replicates was conducted. Results showed that photosystem photochemical efficiency (Fv/Fm II under drought stress (60% FC as well as lower levels of bentonite superabsorbent polymer reduced. The minimum and maximum proline content were obtained in 0.3% bentonite, 100% FC and 0 benetonite, 60% FC, respectively. The lowest and highest phenolic compounds was corresponded to the highest levels in both super absorbents and control respectively, so that the super absorbent and bentonite, reduced phenolic compounds by 62.65 and 66.21% compared to control. 0 and 0.15 wt % bentonite in high drought stress (60% FC showed the highest and 0.3 wt % bentonite and 100% FC attained the lowest level of antioxidant activity. Control bentonite treatment beds at 60% FC and beds containing 0.3 wt. % bentonite in 100% FC, showed the lowest and the highest total carbohydrate content respectively. Results of this study indicate that bentonite can reduce the negative effects of drought stress similar to artificial super absorbent.

  7. Diurnal and Seasonal Responses of High Frequency Chlorophyll Fluorescence and PRI Measurements to Abiotic Stress in Almonds

    Science.gov (United States)

    Bambach-Ortiz, N. E.; Paw U, K. T.

    2016-12-01

    Plants have evolved to efficiently utilize light to synthesize energy-rich carbon compounds, and at the same time, dissipate absorbed but excessive photon that would otherwise transfer excitation energy to potentially toxic reactive oxygen species (ROS). Nevertheless, even the most rapidly growing plants with the highest rates of photosynthesis only utilize about half of the light their leaves absorb during the hours of peak irradiance in sun-exposed habitats. Usually, that daily peak of irradiance coincides with high temperature and a high vapor pressure deficit, which are conditions related to plant stomata closure. Consequently, specially in water stressed environments, plants need to have mechanisms to dissipate most of absorbed photons. Plants avoid photo-oxidative damage of the photosynthetic apparatus due to the formation of ROS under excess light using different mechanisms in order to either lower the amount of ROS formation or detoxify already formed ROS. Photoinhibition is defined as a reduction in photosynthetic activity due largely to a sustained reduction in the photochemical efficiency of Photosystem II (PSII), which can be assessed by monitoring Chlorophyll a fluorescence (ChlF). Alternatively, monitoring abiotic stress effects upon photosynthetic activity and photoinhibition may be possible using high frequency spectral reflectance sensors. We aim to find the potential relationships between high frequency PRI and ChlF as indicators of photoinhibition and permanent photodamage at a seasonal scale. Preliminary results show that PRI responses are sensitive to photoinhibition, but provide a poor representation of permanent photodamage observed at a seasonal scale.

  8. High-throughput growth prediction for Lactuca sativa L. seedlings using chlorophyll fluorescence in a plant factory with artificial lighting

    Directory of Open Access Journals (Sweden)

    Shogo eMoriyuki

    2016-03-01

    Full Text Available Poorly grown plants that result from differences in individuals lead to large profit losses for plant factories that use large electric power sources for cultivation. Thus, identifying and culling the low-grade seedlings at an early stage, using so-called seedling diagnosis technology, plays an important role in avoiding large losses in plant factories. In this study, we developed a high-throughput diagnosis system using the measurement of chlorophyll fluorescence (CF in a commercial large-scale plant factory, which produces about 5,000 lettuce plants every day. At an early stage (6 days after sowing, a CF image of 6,000 seedlings was captured every 4 hours on the final greening day by a high-sensitivity CCD camera and an automatic transferring machine, and biological indices were extracted. Using machine learning, plant growth can be predicted with a high degree of accuracy based on biological indices including leaf size, amount of CF, and circadian rhythms in CF. Growth prediction was improved by addition of temporal information on CF. The present data also provide new insights into the relationships between growth and temporal information regulated by the inherent biological clock.

  9. Herbicidal effects of harmaline from Peganum harmala on photosynthesis of Chlorella pyrenoidosa: probed by chlorophyll fluorescence and thermoluminescence.

    Science.gov (United States)

    Deng, Chunnuan; Shao, Hua; Pan, Xiangliang; Wang, Shuzhi; Zhang, Daoyong

    2014-10-01

    The herbicidal effects of harmaline extracted from Peganum harmala seed on cell growth and photosynthesis of green algae Chlorella pyrenoidosa were investigated using chlorophyll a fluorescence and thermoluminescence techniques. Exposure to harmaline inhibited cell growth, pigments contents and oxygen evolution of C. pyrenoidosa. Oxygen evolution was more sensitive to harmaline toxicity than cell growth or the whole photosystem II (PSII) activity, maybe it was the first target site of harmaline. The JIP-test parameters showed that harmaline inhibited the donor side of PSII. Harmaline decreased photochemical efficiency and electron transport flow of PSII but increased the energy dissipation. The charge recombination was also affected by harmaline. Amplitude of the fast phase decreased and the slow phase increased at the highest level of harmaline. Electron transfer from QA(-) to QB was inhibited and backward electron transport flow from QA(-) to oxygen evolution complex was enhanced at 10 μg mL(-1) harmaline. Exposure to 10 μg mL(-1) harmaline caused appearance of C band in thermoluminescence. Exposure to 5 μg mL(-1) harmaline inhibited the formation of proton gradient. The highest concentration of harmaline treatment inhibited S3QB(-) charge recombination but promoted formation of QA(-)YD(+) charge pairs. P. harmala harmaline may be a promising herbicide because of its inhibition of cell growth, pigments synthesis, oxygen evolution and PSII activities.

  10. Early stage toxicity of excess copper to photosystem II of Chlorella pyrenoidosa-OJIP chlorophyll a fluorescence analysis

    Institute of Scientific and Technical Information of China (English)

    XIA Jianrong; TIAN Qiran

    2009-01-01

    Acute toxicity of excess Cu on the photosynthetic performance of Chlorella pyrenoidosa was examined by using chlorophyll a fluorescence transients and JIP-test after exposure to elevated Cu concentrations for a short period of time.High Cu concentration resulted in a significant suppression in photosynthesis and respiration.The absorption flux (ABS/RC) per PSⅡ reaction center increased with increasing Cu concentration,but the electron transport flux (ET_0/RC) decreased.Excess Cu had an insignificant effect on the trapping flux (TR_0/RC).The decline in the efficiency with which a trapped exciton can move an electron into the electron transport chain further than QA- (ψ_o),the maximal quantum yield of primary photochemistry (φP_o),and the quantum yield of electron transport (φE_o) were also observed.The amount of active PSⅡ reaction centers per excited cross section (RC/CS) was also in consistency with the change of photosynthesis when cells were exposed to excess Cu concentration.JIP-test parameters had a good linear relationship with photosynthetic O_2 evolution.These results suggested that the decrease of photosynthesis in exposure to excess Cu may be a result of the inactivation of PSⅡ reaction centers and inhibition of electron transport in the acceptor side.

  11. A convenient method for determination of quizalofop-p-ethyl based on the fluorescence quenching of eosin Y in the presence of Pd(II)

    Science.gov (United States)

    Wu, Huan; Zhao, Yanmei; Tan, Xuanping; Zeng, Xiaoqing; Guo, Yuan; Yang, Jidong

    2017-03-01

    A convenient fluorescence quenching method for determination of Quizalofop-p-ethyl(Qpe) was proposed in this paper. Eosin Y(EY) is a red dye with strong green fluorescence (λex/λem = 519/540 nm). The interaction between EY, Pd(II) and Qpe was investigated by fluorescence spectroscopy, resonance Rayleigh scattering(RRS) and UV-Vis absorption. Based on changes in spectrum, Pd(II) associated with Qpe giving a positively charged chelate firstly, then reacted with EY through electrostatic and hydrophobic interaction formed ternary chelate could be demonstrated. Under optimum conditions, the fluorescence intensity of EY could be quenched by Qpe in the presence of Pd(II) and the RRS intensity had a remarkable enhancement, which was directly proportional to the Qpe concentration within a certain concentration range, respectively. Based on the fluorescence quenching of EY-Pd(II) system by Qpe, a novel, convenient and specific method for Qpe determination was developed. To our knowledge, this is the first fluorescence method for determination of Qpe was reported. The detection limit for Qpe was 20.3 ng/mL and the quantitative determination range was 0.04-1.0 μg/mL. The method was highly sensitive and had larger detection range compared to other methods. The influence of coexisting substances was investigated with good anti-interference ability. The new analytical method has been applied to determine of Qpe in real samples with satisfactory results.

  12. Systematic investigation of the influence of CdTe QDs size on the toxic interaction with human serum albumin by fluorescence quenching method

    Science.gov (United States)

    Xiao, Jianbo; Bai, Yalong; Wang, Yuanfeng; Chen, Jingwen; Wei, Xinlin

    2010-06-01

    Quantum dots (QDs) are complementary tools to the organic fluorescent dyes used in biological system. Investigation of QDs biological toxicity has attracted great interest for their depth application. Here, the fluorescence quenching method was used to investigate the influence of CdTe QDs size on the toxic interaction with human serum albumin (HSA). Two aqueous-compatible CdTe QDs with maximum emission of 535 nm (green-emitting QDs, G-QDs, 2.04 nm) and 654 nm (red-emitting QDs, R-QDs, 3.79 nm) were tested. The fluorescence quenching results indicated that the quenching effect of QDs on HSA fluorescence depended on the size and the nature of quenching is not dynamic but probably static, resulting in forming QDs-HSA complexes. The binding constants and the number of binding sites between R-QDs and HSA were higher than those of G-QDs. The results illustrated that the size of CdTe quantum dots affected the affinity for HSA and the increasing size of QDs enhanced the affinity for HSA. The values of lg Ka are proportional to the number of binding sites ( n). This result confirms the method used here is suitable to study the toxic interaction between QDs and HSA.

  13. Electric field effects on internal conversion : An alternative mechanism for field-induced fluorescence quenching of MEH-PPV and its oligomers in the low concentration limit

    NARCIS (Netherlands)

    Smith, Timothy M.; Kim, Jung; Peteanu, Linda A.; Wildeman, Jurjen

    2007-01-01

    In a previously published study (J. Phys. Chem. B 2006, 110, 7732-7742), we reported field-induced fluorescence quenching in both poly[2-methoxy,5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and several model oligomers in solvent glass matrices at high dilution (<0.1% by weight). The observ

  14. Internally quenched fluorescent peptide libraries with randomized sequences designed to detect endopeptidases.

    Science.gov (United States)

    Oliveira, Lilian C G; Silva, Vinícius O; Okamoto, Debora N; Kondo, Marcia Y; Santos, Saara M B; Hirata, Isaura Y; Vallim, Marcelo A; Pascon, Renata C; Gouvea, Iuri E; Juliano, Maria A; Juliano, Luiz

    2012-02-01

    Identification of synthetic peptide substrates for novel peptidases is an essential step for their study. With this purpose we synthesized fluorescence resonance energy transfer (FRET) peptide libraries Abz (or MCA)-GXXXXXQ-EDDnp and Abz (or MCA)-GXXZXXQ-EDDnp, where X consists of an equimolar mixture of all amino acids, the Z position is fixed with one of the proteinogenic amino acids (cysteine was excluded), Abz (ortho-aminobenzoic acid) or MCA ([7-amino-4-methyl]coumarin) is the fluorescence donor and Q-EDDnp (glutamine-[N-(2,4-dinitrophenyl)-ethylenediamine]) is the fluorescence acceptor. The peptide libraries MCA-GXXX↓XXQ-EDDnp and MCA-GXXZ↓XXQ-EDDnp were cleaved as indicated (↓) by trypsin, chymotrypsin, cathepsin L, pepsin A, and Eqolisin as confirmed by Edman degradation of the products derived from the digestion of these libraries. The best hydrolyzed Abz-GXXZXXQ-EDDnp sublibraries by these proteases, including Dengue 2 virus NS2B-NS3 protease, contained amino acids at the Z position that are reported to be well accepted by their S(1) subsite. The pH profiles of the hydrolytic activities of these canonical proteases on the libraries were similar to those reported for typical substrates. The FRET peptide libraries provide an efficient and simple approach for detecting nanomolar concentrations of endopeptidases and are useful for initial specificity characterization as performed for two proteases secreted by a Bacillus subtilis.

  15. Upward and downward solar-induced chlorophyll fluorescence yield indices of four tree species as indicators of traffic pollution in Valencia.

    Science.gov (United States)

    Van Wittenberghe, Shari; Alonso, Luis; Verrelst, Jochem; Hermans, Inge; Delegido, Jesús; Veroustraete, Frank; Valcke, Roland; Moreno, José; Samson, Roeland

    2013-02-01

    Passive steady-state chlorophyll fluorescence (Fs) provides a direct diagnosis of the functional status of vegetation photosynthesis. With the prospect of mapping Fs using remote sensing techniques, field measurements are mandatory to understand to which extent Fs allows detecting plant stress in different environments. Trees of four common species in Valencia were classified in either a low or a high local traffic exposure class based on their leaf magnetic value. Upward and downward hyperspectral fluorescence yield (FY) and indices based on the two Fs peaks (at 687 and 741 nm) were calculated. FY indices of P. canariensis and P. x acerifolia were significantly different between the two traffic exposure classes defined, but not for C. australis nor M. alba. While chlorophyll content could not indicate the difference between low and high traffic exposure, the FY(687)/FY(741) peak ratio increased significantly (p < 0.05) for both leaf sides for the higher traffic exposure class.

  16. Effects of NaCl Stress on Chlorophyll Fluorescence Parameters in Cinnamomum japonicum var. chenii%NaCl胁迫对普陀樟叶绿素荧光参数的影响

    Institute of Scientific and Technical Information of China (English)

    李影丽; 汪奎宏; 杜国坚; 许利群; 杨华; 肖纪军

    2008-01-01

    [Objective] Study on the changes of chlorophyll fluorescence parameters in Cinnamomum japonicum var. chenii under NaCl stress. [Method] The seedling growth increment, chlorophyll content and chlorophyll fluorescence parameters in leaves of 1-year old Cinnamomum japonicum var. chenii were investigated in field experiment. [Result] Under NaCl stress, seedling growth increment reduced and the chlorophyll content decreased to a stable value; changes of Fv/Fm and Fv/Fo showed identical increasing trend and double peak type. With the aggravation of salt stress, most variations were ob- served in Fo, correlations among chlorophyll fluorescence parameters presented "rise-drop" trend (in the treatment of 7 g/L NaCl). [Condusion] Cinna-momum japonicum var. chenii is endowed with strong salt resistance and wide adaptability.

  17. Effects of different concentrations of nitrogen and phosphorus on chlorophyll biosynthesis,chlorophyll a fluorescence,and photosynthesis In Larix olgensis seedlings

    Institute of Scientific and Technical Information of China (English)

    Wu Chu; Wang Zhengquan; Sun Hailong; Guo Shenglei

    2006-01-01

    In our experiments,one-year-old Larix olgensis seedlings were cultivated in sand,and supplied with solutions with different concentrations of nitrate or phosphate.The effects of nitrogen and phosphorus supply on chlorophyll biosynthesis,total nitrogen content,and photosynthetic rate were studied.The experimental results are listed below: 1) 5-aminolevulinic acid (ALA) synthetic rate increased as nitrate concentrations supplied to larch seedlings increased from 1 to 8 mmol/L.But the rate decreased by 17% when nitrate concentration increased to 16 mmol/L,in contrast to the control.Under phosphate treatments,ALA synthetic rates were similar to those under nitrate treatments.The activities of porphobilinogen (PBG)synthase reached a maximum when larch seedlings were supplied with 8 mmol/L of nitrate or 1 mmol/L of phosphate.2) When larch seedlings were supplied with 8 mmol/L of nitrate and 0.5 mmol/L of phosphate,the contents of chlorophyll a,chlorophyll b,total chlorophyll,and carotenoids reached a maximum.The total nitrogen contents in leaves increased as nitrate concentrations increased.3) When phosphate concentrations increased from 0.125 to 1 mmol/L,the total nitrogen contents in leaves slightly increased;however,continuous increase of phosphate concentrations resulted in the decrease in total nitrogen contents in leaves.When nitrate concentrations increased from 1 to 8 mmol/L,soluble protein contents in leaves increased in general,and continuous increase of nitrate concentrations induced a decrease in soluble protein contents in leaves.Under treatment of 0.25 mmol/L of phosphate,the soluble protein contents reached a maximum.4) In general,Fv/Fm increased as nitrate concentrations increased from 1 to 8 mmol/L,and continuous increase of nitrate concentration resulted in decrease in FvlFm.The similar changes occurred under phosphate treatments.As nitrate concentrations increased from 1 to 8 mmol/L,photosynthetic rates gradually increased,but when nitrate

  18. Effects of habitat light conditions on the excitation quenching pathways in desiccating Haberlea rhodopensis leaves: an Intelligent FluoroSensor study.

    Science.gov (United States)

    Solti, Ádám; Lenk, Sándor; Mihailova, Gergana; Mayer, Péter; Barócsi, Attila; Georgieva, Katya

    2014-01-05

    Resurrection plants can survive dehydration to air-dry state, thus they are excellent models of understanding drought and dehydration tolerance mechanisms. Haberlea rhodopensis, a chlorophyll-retaining resurrection plant, can survive desiccation to relative water content below 10%. Leaves, detached from plants of sun and shade habitats, were moderately (∼50%) dehydrated in darkness. During desiccation, chlorophyll a fluorescence was detected by the recently innovated wireless Intelligent FluoroSensor (IFS) chlorophyll fluorometer, working with three different detectors: a pulse-amplitude-modulated (PAM) broadband channel and two channels to measure non-modulated red and far-red fluorescence. No change in area-based chlorophyll content of leaves was observed. The maximal quantum efficiency of photosystem II decreased gradually in both shade and sun leaves. Shade leaves could not increase antennae-based quenching, thus inactivated photosystem II took part in quenching of excess irradiation. Sun leaves seemed to be pre-adapted to quench excess light as they established an intensive increase in antennae-based non-photochemical quenching parallel to desiccation. The higher far-red to red antennae-based quenching may sign light-harvesting complex reorganization. Thus, compared to PAM, IFS chlorophyll fluorometer has additional benefits including (i) parallel estimation of changes in the Chl content and (ii) prediction of underlying processes of excitation energy quenching.

  19. Silver Nanoparticle-Based Fluorescence-Quenching Lateral Flow Immunoassay for Sensitive Detection of Ochratoxin A in Grape Juice and Wine

    Directory of Open Access Journals (Sweden)

    Hu Jiang

    2017-02-01

    Full Text Available A silver nanoparticle (AgNP-based fluorescence-quenching lateral flow immunoassay with competitive format (cLFIA was developed for sensitive detection of ochratoxin A (OTA in grape juice and wine samples in the present study. The Ru(phen 3 2 + -doped silica nanoparticles (RuNPs were sprayed on the test and control line zones as background fluorescence signals. The AgNPs were designed as the fluorescence quenchers of RuNPs because they can block the exciting light transferring to the RuNP molecules. The proposed method exhibited high sensitivity for OTA detection, with a detection limit of 0.06 µg/L under optimized conditions. The method also exhibited a good linear range for OTA quantitative analysis from 0.08 µg/L to 5.0 µg/L. The reliability of the fluorescence-quenching cLFIA method was evaluated through analysis of the OTA-spiked red grape wine and juice samples. The average recoveries ranged from 88.0% to 110.0% in red grape wine and from 92.0% to 110.0% in grape juice. Meanwhile, less than a 10% coefficient variation indicated an acceptable precision of the cLFIA method. In summary, the new AgNP-based fluorescence-quenching cLFIA is a simple, rapid, sensitive, and accurate method for quantitative detection of OTA in grape juice and wine or other foodstuffs.

  20. Species-specific and seasonal differences in chlorophyll fluorescence and photosynthetic light response among three evergreen species in a Madrean sky island mixed conifer forest

    Science.gov (United States)

    Potts, D. L.; Minor, R. L.; Braun, Z.; Barron-Gafford, G. A.

    2012-12-01

    Unlike the snowmelt-dominated hydroclimate of more northern mountainous regions, the hydroclimate of the Madrean sky islands is characterized by snowmelt and convective storms associated with the North American Monsoon. These mid-summer storms trigger biological activity and are important drivers of primary productivity. For example, at the highest elevations where mixed conifer forests occur, ecosystem carbon balance is influenced by monsoon rains. Whereas these storms' significance is increasingly recognized at the ecosystem scale, species-specific physiological responses to the monsoon are poorly known. Prior to and following monsoon onset, we measured pre-dawn and light-adapted chlorophyll fluorescence as well as photosynthetic light response in southwestern white pine (Pinus strobiformis), ponderosa pine (Pinus ponderosa), and Douglas fir (Pseudotsuga menziesii) in a Madrean sky island mixed conifer forest near Tucson, Arizona. Photochemical quenching (qp), an indicator of the proportion of open PSII reaction centers, was greatest in P. strobiformis and least in P. menziesii and increased in response to monsoon rains (repeated-measures ANOVA; species, F2,14 = 6.17, P = 0.012; time, F2,14= 8.17, P = 0.013). In contrast, non-photochemical quenching (qN), an indicator of heat dissipation ability, was greatest in P. ponderosa and least in P. menziesii, but was not influenced by monsoon onset (repeated-measures ANOVA; species, F2,12 = 4.18, P = 0.042). Estimated from leaf area-adjusted photosynthetic light response curves, maximum photosynthetic rate (Amax) was greatest in P. ponderosa and least in P. menziesii (repeated-measures ANOVA; species, F2,8= 40.8, P = 0.001). Surprisingly, while the monsoon positively influenced Amax among P. ponderosa and P. strobiformis, Amax of P. menziesii declined with monsoon onset (repeated-measures ANOVA; species x time, F2,8 = 13.8, P = 0.002). Calculated as the initial slope of the photosynthetic light response curve, light

  1. Fluorescence quenching and photobleaching in Au/Rh6G nanoassemblies: impact of competition between radiative and non-radiative decay

    Science.gov (United States)

    Dong, L.; Ye, F.; Hu, J.; Popov, S.; Friberg, A. T.; Muhammed, M.

    2011-04-01

    Fluorescence quenching from nanoassemblies formed by Rhodamine 6G and gold nanoparticles (Au NPs) of 2.6 nm radius has been investigated. The presence of Au NPs also induces long-term degradation of the photostability (photobleaching) of Rhodamine 6G used as gain medium in a Fabry-Perot laser cavity. We found that the degradation gets profound when the Au NPs concentration is significantly increased. Calculation of the radiative rate and direct time-resolved measurement of the fluorescence decay indicates that both the decrease of radiative decay rate and increase of non-radiative decay rate are responsible for the fluorescence quenching and photostability degradation. An energy transfer from the dye molecules to gold nanoparticles is dominating within the small distance between them and suppresses the quantum efficiency of Rhodamine 6G drastically. In long time scale, the photobleaching rate was slowing down, and laser output intensity reached a stabilized level which depends on the gold nanoparticles concentration.

  2. Efficient fluorescence quenching in electrochemically exfoliated graphene decorated with gold nanoparticles

    Science.gov (United States)

    Hurtado-Morales, M.; Ortiz, M.; Acuña, C.; Nerl, H. C.; Nicolosi, V.; Hernández, Y.

    2016-07-01

    High surface area graphene sheets were obtained by electrochemical exfoliation of graphite in an acid medium under constant potential conditions. Filtration and centrifugation processes played an important role in order to obtain stable dispersions in water. Scanning electron microscopy and transmission electron microscopy imaging revealed highly exfoliated crystalline samples of ∼5 μm. Raman, Fourier transform infrared and x-ray photoelectron spectroscopy further confirmed the high quality of the exfoliated material. The electrochemically exfoliated graphene (EEG) was decorated with gold nanoparticles (AuNPs) using sodium cholate as a buffer layer. This approach allowed for a non-covalent functionalization without altering the desirable electronic properties of the EEG. The AuNP-EEG samples were characterized with various techniques including absorbance and fluorescence spectroscopy. These samples displayed a fluorescence signal using an excitation wavelength of 290 nm. The calculated quantum yield (Φ) for these samples was 40.04%, a high efficiency compared to previous studies using solution processable graphene.

  3. SENSITIVITY TO ENVIRONMENTAL STRESS OF PRATA,JAPIRA AND VITÓRIA BANANA CULTIVARS PROVEN BY CHLOROPHYLL a FLUORESCENCE

    Directory of Open Access Journals (Sweden)

    PRISCILA NOBRES DOS SANTOS

    Full Text Available ABSTRACT This study aimed to evaluate the physiological responses to environmental stress during pre- and post-harvest of the following banana cultivars: Prata (AAB, Japira (AAAB and Vitoria (AAAB. Analyses were carried out on young plants at vegetative stage (daughter-plant and adult plants at reproductive stage (motherplant. The experimental design was completely randomized. In the in vivo pre-harvest analysis were used seven replications, in a factorial scheme (3x2x2, three cultivars and two stages (vegetative and reproductive and two collection periods (March and June. For the analysis of post-harvest quality were used five replications in a factorial design (3x2x5, corresponding to three cultivars, two development stages and five periods of post-harvest analysis, carried out every two days from stage 4 of fruit ripening. The chlorophyll a fluorescence emission kinetics showed low photochemical performance of the three cultivars in June, a period characterized by lower temperatures and water deficit. Prata was the cultivar with the lowest tolerance to abiotic physiological behavior changes, which also reflected in fruit quality, because there was a change in physical and physicochemical parameters. Japira and Vitoria cultivars showed similar physiological responses in the pre- and post-harvest periods, according to their phylogenetic proximity. The total performance index, i.e., the conservation of energy absorbed by PSII up to the reduction of the final PSI acceptors (PItotal and the di-malonic aldehyde (MDA content were significantly higher in Japira and Vitoria cultivars compared to Prata cultivar in the reproductive phase. There was no significant change in the potential quantum efficiency of PSII (FV / FM = jP0 among the three cultivars. It was concluded that Japira and Vitoria cultivars showed greater plasticity to tolerate or even adapt to abiotic variations keeping higher fruit yield. PItotal is the most sensitive parameter during

  4. Characteristics of Gas Exchange, Chlorophyll Fluorescence and Expression of Key Enzymes in Photosynthesis During Leaf Senescence in Rice Plants

    Institute of Scientific and Technical Information of China (English)

    Xiao-Yan WENG; Hong-Xia XU; De-An JIANG

    2005-01-01

    Gas exchange, chlorophyll (Chl) fluorescence, photosynthetic pigments, and the expression of Rubisco and Rubisco activase in flag leaves of rice (Oryza sativa L.) from the heading to mature grain stage were investigated. The results showed that the photosynthetic capacity declined after full expansion of flag leaves. The decline of photosynthetic rate (Pn) in two cultivars during natural senescence was accompanied by a decrease in Chl content, as well as in the Rubisco and Rubisco activase contents. The Rubisco and Rubisco activase contents in Zhenong 966 decreased faster than that in Zhenong 952. The Pn diminished without a decrease in intercellular CO2 concentration during the early senescence of flag leaves, indicating that lower photosynthetic capacity is not caused by stomatal limitation but by reduced carboxylation efficiency. During the senescence of flag leaves, the correlation between the change in photosynthetic capacity and the variation in the abundance of Rubisco and Rubisco activase suggested that the decline in Pn of flag leaves could be attributed to the lower level of rbcS and rca transcripts. The (φ)PSⅡ and the electron transport rate appeared in the same rate as Pn. However, excitation pressure (1-qP) showed a different pattern and there was an inverse linear correlation between increased excitation pressure and the reduced Rubisco. Therefore, it is likely that the increased excitation pressure resulted from saturation of the electron transport chain, owing to a limitation of the reductant used by the Calvin cycle; in addition, the change in excitation pressure could further mediate the expression of the rbcS and rca genes, resulting in a fast reduction in Rubisco content.

  5. Atividade da redutase do nitrato e fluorescência da clorofila a em mamoeiro Nitrate reductase activity and chlorophyll a fluorescence in papaya

    Directory of Open Access Journals (Sweden)

    Renata Venturim Fontes

    2008-03-01

    correlation r= 0,740 and coefficient of determination r²= 0,706 and Sunrise Solo 72/12 (coefficient of correlation r= 0,960 and coefficient of determination r²= 0,945. These results suggest that there is a correlation between chlorophyll a fluorescence and nitrate reductase activity in these plants.

  6. The Sakaguchi reaction product quenches phycobilisome fluorescence, allowing determination of the arginine concentration in cells of Anabaena strain PCC 7120.

    Science.gov (United States)

    Ke, Shan; Haselkorn, Robert

    2013-01-01

    The filamentous cyanobacterium Anabaena fixes nitrogen in specialized cells called heterocysts. The immediate product of fixation, ammonia, is known to be assimilated by addition to glutamate to make glutamine. How fixed nitrogen is transported along the filament to the 10 to 20 vegetative cells that separate heterocysts is unknown. N-fixing heterocysts accumulate an insoluble polymer containing aspartate and arginine at the cell poles. Lockau's group has proposed that the polymer is degraded at the poles to provide a mobile carrier, arginine, to the vegetative cells (R. Richter, M. Hejazi, R. Kraft, K. Ziegler, and W. Lockau, Eur. J. Biochem. 263:163-169, 1999). We wished to use the Sakaguchi reaction for arginine to determine the relative cellular concentration of arginine along the filament. At present, the methods for measuring absorption of the Sakaguchi reaction product at 520 nm are insufficiently sensitive for that purpose. However, that product quenches the fluorescence of phycobiliproteins, which we have adapted to a determination of arginine. Our results are consistent with the proposal that arginine is a principal nitrogen carrier from heterocysts to vegetative cells in Anabaena.

  7. Highly sensitive and adaptable fluorescence-quenched pair discloses the substrate specificity profiles in diverse protease families

    Science.gov (United States)

    Poreba, Marcin; Szalek, Aleksandra; Rut, Wioletta; Kasperkiewicz, Paulina; Rutkowska-Wlodarczyk, Izabela; Snipas, Scott J.; Itoh, Yoshifumi; Turk, Dusan; Turk, Boris; Overall, Christopher M.; Kaczmarek, Leszek; Salvesen, Guy S.; Drag, Marcin

    2017-01-01

    Internally quenched fluorescent (IQF) peptide substrates originating from FRET (Förster Resonance Energy Transfer) are powerful tool for examining the activity and specificity of proteases, and a variety of donor/acceptor pairs are extensively used to design individual substrates and combinatorial libraries. We developed a highly sensitive and adaptable donor/acceptor pair that can be used to investigate the substrate specificity of cysteine proteases, serine proteases and metalloproteinases. This novel pair comprises 7-amino-4-carbamoylmethylcoumarin (ACC) as the fluorophore and 2,4-dinitrophenyl-lysine (Lys(DNP)) as the quencher. Using caspase-3, caspase-7, caspase-8, neutrophil elastase, legumain, and two matrix metalloproteinases (MMP2 and MMP9), we demonstrated that substrates containing ACC/Lys(DNP) exhibit 7 to 10 times higher sensitivity than conventional 7-methoxy-coumarin-4-yl acetic acid (MCA)/Lys(DNP) substrates; thus, substantially lower amounts of substrate and enzyme can be used for each assay. We therefore propose that the ACC/Lys(DNP) pair can be considered a novel and sensitive scaffold for designing substrates for any group of endopeptidases. We further demonstrate that IQF substrates containing unnatural amino acids can be used to investigate protease activities/specificities for peptides containing post-translationally modified amino acids. Finally, we used IQF substrates to re-investigate the P1-Asp characteristic of caspases, thus demonstrating that some human caspases can also hydrolyze substrates after glutamic acid. PMID:28230157

  8. Selective Detection of Mercury(Ⅱ) and Copper(Ⅱ) Based on the Opposite Size-dependent Fluorescence Quenching of CdTe Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    XIA Yun-Sheng; CAO Chun; ZHU Chang-Qing

    2007-01-01

    Three different size CdTe quantum dots (QDs) capped by 3-mercaptopropionic acid (MPA) have been prepared in aqueous solutions,and their interactions with Cu2+ and Hg2+ have been investigated.The opposite size-dependent fluorescence quenching of CdTe QDs by Hg2+ and Cu2+ was observed: Hg2+ quenched smaller particles more efficiently than larger ones while larger particles were more markedly quenched by Cu2+.Based on the different size responses,Hg2+ and Cu2+ were respectively detected with high sensitivity and selectivity,for the first time,using the QDs with different sizes but the same components and capping ligands.

  9. Chlorophyll fluorescence of tropical tree species in a semi-deciduous forest gap Fluorescência da clorofila de espécies arbóreas tropicais em uma clareira de floresta semidecídua

    Directory of Open Access Journals (Sweden)

    Rafael Vasconcelos Ribeiro

    2004-02-01

    Full Text Available The characterization of different ecological groups in a forest formation/succession is unclear. To better define the different successional classes, we have to consider ecophysiological aspects, such as the capacity to use or dissipate the light energy available. The main objective of this work was to assess the chlorophyll fluorescence emission of tropical tree species growing in a gap of a semi-deciduous forest. Three species of different ecological groups were selected: Croton floribundus Spreng. (pioneer, P, Astronium graveolens Jacq. (early secondary, Si, and Esenbeckia febrifuga A. Juss. (late secondary, St. The potential (Fv/Fm and effective (deltaF/Fm' quantum efficiency of photosystem II, apparent electron transport rate (ETR, non-photochemical (qN and photochemical (qP quenching of fluorescence were evaluated, using a modulated fluorometer, between 7:30 and 11:00 h. Values of Fv/Fm remained constant in St, decreasing in P and Si after 9:30 h, indicating the occurrence of photoinhibition. Concerning the measurements taken under light conditions (deltaF/Fm', ETR, qP and qN, P and Si showed better photochemical performance, i.e., values of deltaF/Fm', ETR and qP were higher than St when light intensity was increased. Values of qN indicated that P and Si had an increasing tendency of dissipating the excess of energy absorbed by the leaf, whereas the opposite was found for St. The principal component analysis (PCA, considering all evaluated parameters, showed a clear distinction between St, P and Si, with P and Si being closer. The PCA results suggest that chlorophyll fluorescence may be a potential tool to differentiate tree species from distinct successional groups.A caracterização dos diferentes grupos ecológicos envolvidos nos processos de formação/sucessão florestal é ainda pouco precisa. Para melhor distinção das classes sucessionais deve-se levar em consideração aspectos ecofisiológicos, como a capacidade de

  10. Unraveling the exciton quenching mechanism of quantum dots on antimony-doped SnO₂ films by transient absorption and single dot fluorescence spectroscopy.

    Science.gov (United States)

    Song, Nianhui; Zhu, Haiming; Liu, Zheng; Huang, Zhuangqun; Wu, David; Lian, Tianquan

    2013-02-26

    Integrating quantum dots (QDs) into modern optoelectronic devices requires an understanding of how a transparent conducting substrate affects the properties of QDs, especially their excited-state dynamics. Here, the exciton quenching dynamics of core/multishell (CdSe/CdS(3ML)ZnCdS(2ML)ZnS(2ML)) quantum dots deposited on glass, tin oxide (SnO₂), and antimony (Sb)-doped tin oxide (ATO) films are studied by transient absorption and single QD fluorescence spectroscopic methods. By comparing ensemble-averaged fluorescence decay and transient absorption kinetics, we show that, for QDs on SnO₂, the exciton is quenched by electron transfer from the QD to SnO₂. At the QD-ATO interface, much faster exciton quenching rates are observed and attributed to fast Auger recombination in charged QDs formed by Fermi level equilibration between the QD and n-doped ATO. Single QDs on SnO₂ and ATO show similar blinking dynamics with correlated fluctuations of emission intensities and lifetimes. Compared to QDs on SnO₂, QDs on ATO films show larger variation of average exciton quenching rates, which is attributed to a broad distribution of the number of charges and nature of charging sites on the QD surface.

  11. Effects of SO{sub 2} fumigations on photosynthetic CO{sub 2} gas exchange, chlorophyll a fluorescence emission and antioxidant enzymes in the lichens Evernia prunastri and Ramalina farinacea

    Energy Technology Data Exchange (ETDEWEB)

    Deltoro, V.I.; Gimeno, C.; Calatayud, A.; Barreno, E. [Univ. de Valencia, Inst. `Cavanilles` de Biodiversitat i Biologia Evolutiva, Facultat de Ciencies Biologiques, Burjassot (Spain)

    1999-08-01

    The effects of elevated gaseous SO{sub 2} concentrations in the lichens Evernia prunastri (L.) Ach. and Ramalina farinacea (L.) Ach. were investigated by means of gas exchange, modulated chlorophyll fluorescence analysis and antioxidant enzyme assays. The response to SO{sub 2} of the studied species differed markedly. Net photosynthetic rates were more adversely affected in E. prunastri than in R. farinacea. In addition, processes dependent on thylakoid membrane integrity such as PSII-mediated electron flow and non-photochemical quenching were reduced to a greater extent by exposure to SO{sub 2} in E. prunastri. Moreover, the ability to re-oxidize the quinone pool was lower in this species. Finally, the activity of chloroplastidic and cytoplasmic antioxidant enzymes was decreased in E. prunastri in response to fumigations but increased in R. farinacea. The results suggest that the ability to process and deal with the SO{sub 2} once it has been absorbed must play a role in determining the sensitivity of these lichen species to this air pollutant. (au)

  12. Chlorophyll fluorescence imaging of photosynthetic activity and pigment contents of the resurrection plants Ramonda serbica and Ramonda nathaliae during dehydration and rehydration.

    Science.gov (United States)

    Gashi, Bekim; Babani, Fatbardha; Kongjika, Efigjeni

    2013-07-01

    The desiccation-tolerant plants of the R. serbica and R. nathaliae are resurrection plants which are able to fully recover their physiological function after anabiosis. A comparison of chlorophyll fluorescence imaging and photosynthetic pigment contents responses of R. serbica and, for the first time, R. nathaliae to dehydration and rehydration were investigated. For this purpose, plants after collection from their natural habitats were kept fully watered for 14 days at natural condition. The experiment was conducted with mature leaves of both species. R. serbica and R. nathaliae plants were dehydrated to 5.88 % and 7.87 % relative water content (RWC) by withholding water for 15 days, afterwards the plants were rehydrated for 72 hours to 94.67 % and 97.02 % RWC. During desiccation, R. serbica plants preserved the chlorophyll content about 84 %, while R. nathaliae about 90 %. During dehydration when RWC were more than 40 %, photochemical efficiency of PSII for photochemistry, the Fv/Fm ratio, decreased about 40 % in R. nathaliae plants, but a strong reduction with 60 % was recorded for R. serbica. Following rehydration, the Fv/Fm ratio recovered more rapidly in R. nathaliae. The higher photosynthetic rates could also be detected via imaging the chlorophyll fluorescence decrease ratio Rfd, which possessed higher values after rehydration leaves of R. nathaliae as compared to R. serbica. The results showed that the photosynthetic activity and chlorophyll contents after rehydration are recovered more rapidly in R. nathaliae in comparison to R. serbica.

  13. Estimation of vegetation photosynthetic capacity from space-based measurements of chlorophyll fluorescence for terrestrial biosphere models.

    Science.gov (United States)

    Zhang, Yongguang; Guanter, Luis; Berry, Joseph A; Joiner, Joanna; van der Tol, Christiaan; Huete, Alfredo; Gitelson, Anatoly; Voigt, Maximilian; Köhler, Philipp

    2014-12-01

    Photosynthesis simulations by terrestrial biosphere models are usually based on the Farquhar's model, in which the maximum rate of carboxylation (Vcmax ) is a key control parameter of photosynthetic capacity. Even though Vcmax is known to vary substantially in space and time in response to environmental controls, it is typically parameterized in models with tabulated values associated to plant functional types. Remote sensing can be used to produce a spatially continuous and temporally resolved view on photosynthetic efficiency, but traditional vegetation observations based on spectral reflectance lack a direct link to plant photochemical processes. Alternatively, recent space-borne measurements of sun-induced chlorophyll fluorescence (SIF) can offer an observational constraint on photosynthesis simulations. Here, we show that top-of-canopy SIF measurements from space are sensitive to Vcmax at the ecosystem level, and present an approach to invert Vcmax from SIF data. We use the Soil-Canopy Observation of Photosynthesis and Energy (SCOPE) balance model to derive empirical relationships between seasonal Vcmax and SIF which are used to solve the inverse problem. We evaluate our Vcmax estimation method at six agricultural flux tower sites in the midwestern US using spaced-based SIF retrievals. Our Vcmax estimates agree well with literature values for corn and soybean plants (average values of 37 and 101 μmol m(-2)  s(-1) , respectively) and show plausible seasonal patterns. The effect of the updated seasonally varying Vcmax parameterization on simulated gross primary productivity (GPP) is tested by comparing to simulations with fixed Vcmax values. Validation against flux tower observations demonstrate that simulations of GPP and light use efficiency improve significantly when our time-resolved Vcmax estimates from SIF are used, with R(2) for GPP comparisons increasing from 0.85 to 0.93, and for light use efficiency from 0.44 to 0.83. Our results support the use of

  14. New Spectral Fitting Method for Full-Spectrum Solar-Induced Chlorophyll Fluorescence Retrieval Based on Principal Components Analysis

    Directory of Open Access Journals (Sweden)

    Xinjie Liu

    2015-08-01

    Full Text Available The full-spectrum Solar-Induced chlorophyll Fluorescence (SIF within the 650-800 nm spectral region can provide important information regarding physiological and biochemical activities in vegetation. This paper proposes a new Full-spectrum Spectral Fitting Method (F-SFM for the retrieval of SIF spectra based on Principal Components Analysis (PCA. Using F-SFM, both the full-spectrum reflectance and SIF within the 650-800 nm region were modeled by PCA based on a training dataset simulated by the Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE model, and the weighting coefficients of the principal components were estimated by the least-squares fitting method. An iterative process was employed to improve the accuracy of the estimation of the reflectance. In each iteration, the SIF spectra retrieved from the last run were removed from the total upwelling radiance to minimize the small contribution of the SIF to the apparent reflectance outside the absorption bands. Then, the F-SFM algorithm was tested using both simulated and field-measured data with different Spectral Resolutions (SRs and Signal-to-Noise Ratios (SNRs. For data with an SR of 0.3 nm and without noise, the Relative Root Mean Square Error (RRMSE was less than 14% within the spectral region that was studied, and the peak-value ratio (SIF735/SIF685 was accurately estimated with an RRMSE of 3.56%. In addition, the F-SFM algorithm proved less sensitive to the SR than the three-band Fraunhofer Line Discrimination (3 FLD and improved FLD (iFLD methods. In the case of the field spectral data with SRs of 3 nm and 0.3 nm, the double-peak shape and the diurnal variation trend of the SIF spectra could be reasonably reconstructed by F-SFM, and the retrieved SIF values at the O2-A and O2-B bands were consistent with those retrieved by 3FLD from data with a high SR (0.3 nm and SNR (1000. Therefore, the F-SFM method can provide full-spectrum SIF information with high accuracy even at

  15. Investigations of ion transport through nanoscale polymer membranes by fluorescence quenching of CdSe/CdS quantum dot/quantum rods.

    Science.gov (United States)

    Merkl, Jan-Philip; Wolter, Christopher; Flessau, Sandra; Schmidtke, Christian; Ostermann, Johannes; Feld, Artur; Mews, Alf; Weller, Horst

    2016-04-14

    Detailed steady-state and time-resolved fluorescence quenching measurements give deep insight into ion transport through nanometer thick diblock copolymer membranes, which were assembled as biocompatible shell material around CdSe/CdS quantum dot in quantum rods. We discuss the role of polymer chain length, intermolecular cross-linking and nanopore formation by analysing electron transfer processes from the photoexcited QDQRs to Cu(II) ions, which accumulate in the polymer membrane. Fluorescence investigations on single particle level additionally allow identifying ensemble inhomogeneities.

  16. Development and validation of a new spectrofluorimetric method for the determination of some beta-blockers through fluorescence quenching of eosin Y. Application to content uniformity test

    Directory of Open Access Journals (Sweden)

    Derayea Sayed M

    2016-01-01

    Full Text Available A simple, rapid, sensitive and economic spectrofluorimetric method has been developed and validated for determination of some β-adrenergic blocking agents namely; betaxolol hydrochloride (BTX, carvedilol (CAR, labetalol hydrochloride (LBT, nebivolol hydrochloride (NEB and propranolol hydrochloride (PRO. The method is based on the quenching effect of the cited drugs on the fluorescence intensity of eosin Y at pH 3.4 (acetate buffer. The fluorescence quenching is due to the formation of an ion-pair complex and was measured without extraction at 545 nm (λex. 301.5 nm. The factors affecting the formation of the ion-pair complex were carefully studied and optimized. Under the optimal conditions, the linear ranges for the relationship between the fluorescence quenching value and the concentration of the investigated drugs were 100-2500, 150-2500 and 50-2250 ng mL-1 for (BTX, CAR, (LBT, NEB and (PRO respectively. The method was validated according to ICH guidelines and was applied for determination of the cited drugs in pharmaceutical dosage forms with excellent recoveries. In addition, content uniformity testing of some commercial dosage forms was checked by the proposed method.

  17. THE INTERACTION EFFECTS OF DIFFERENT CD2+ CONCENTRATIONS AND TEMPERATURE ON THE GROWTH AND CHLOROPHYLL FLUORESCENCE OF 3 MICROALGAL STRAINS%Cd2+浓度、温度及交互作用对3株微藻生长及叶绿素荧光特性的影响

    Institute of Scientific and Technical Information of China (English)

    王帅; 梁英

    2012-01-01

    Chlorophyll fluorescence measurement has several good characteristics, such as very quick, extremely sensitive, non-invasive and non-destructive, thus becomes a widely used technique for the investigation of mechanisms of photosynthesis and to study the effects of various environmental conditions (temperature, salinity, heavy metal stress, nutrient deficiency) on the microalgal photosynthetic reactions, particularly for stress physiology of mi-croalgae. In this study, the interaction effects of different Cd2+ concentrations (Chlorella sp. S 0, 20, 40fimol/L:Nannochloris oculata -. 0, 10, 30fimol/L: Dunaliella salina : 0, 70, 140fimol/L) and different temperature (Chlorella sp. And N. Oculata: 20, 25, 30℃ : D. Salina : 15, 25, 35℃) on the chlorophyll fluorescence parameters (Fv/Fm, Yield, qP and NPQ), relative chlorophyll content and cell density of 3 microalgal strains were reported. The above fluorescence parameters including the ratio of variable to maximal chlorophyll fluorescence (Fv/Fm), which has been shown to be a sensitive indicator of photosynthetic performance and photoinhibition, the actual photochemical efficiency of PSII in the light (ΦPSII), the photochemical quenching (qP) and the non-photochemical quenching (NPQ). The 3 microalgal strains used in the experiment were obtained from the Microalgae Culture Center (MACC), Ocean University of China. Cultures were grown in sterilized seawater enriched with f/2 medium. The salinity was adjusted to 28 by using distilled water, and the light intensity was l00μmol o m-2 o s-1. The results showed that the chlorophyll fluorescence parameters, relative chlorophyll contents and cell densities all decreased obviously in the 3 microalgal strains with the increasing heavy metal (Cd2+ ) concentrations, with the exception of Fv/Fm in N. Oculata, where there was no significant difference between the control and the l0μmol/L Cd2+ concentration treatment. This was primarily due to the stimulation algal growth by

  18. Fluorescence quenching studies on the interaction of catechin-quinone with CdTe quantum dots. Mechanism elucidation and feasibility studies.

    Science.gov (United States)

    Dwiecki, Krzysztof; Neunert, Grażyna; Nogala-Kałucka, Małgorzata; Polewski, Krzysztof

    2015-01-01

    Changes of the photoluminescent properties of QD in the presence of oxidized catechin (CQ) were investigated by absorption, steady-state fluorescence, fluorescence lifetime and dynamic light scattering measurements. Photoluminescence intensity and fluorescence lifetime was decreasing with increasing CQ concentration. Dynamic light scattering technique found the hydrodynamic diameter of QD suspension in water is in range of 45 nm, whereas in presence of CQ increased to mean values of 67 nm. Calculated from absorption peak position of excition band indicated on average QD size of 3.2 nm. Emission spectroscopy and time-resolved emission studies confirmed preservation of electronic band structure in QD-CQ aggregates. On basis of the presented results, the elucidated mechanism of QD fluorescence quenching is a result of the interaction between QD and CQ due to electron transfer and electrostatic attraction. The results of fluorescence quenching of water-soluble CdTe quantum dot (QD) capped with thiocarboxylic acid were used to implement a simple and fast method to determine the presence of native antioxidant quinones in aqueous solutions. Feasibility studies on this method carried out with oxidized catechin showed a linear relation between the QD emission and quencher concentration, in range from 1 up to 200 μM. The wide linear range of concentration dependence makes it possible to apply this method for the fast and sensitive detection of quinones in solutions.

  19. Toxic Effects of Ethyl Cinnamate on the Photosynthesis and Physiological Characteristics of Chlorella vulgaris Based on Chlorophyll Fluorescence and Flow Cytometry Analysis.

    Science.gov (United States)

    Jiao, Yang; Ouyang, Hui-Ling; Jiang, Yu-Jiao; Kong, Xiang-Zhen; He, Wei; Liu, Wen-Xiu; Yang, Bin; Xu, Fu-Liu

    2015-01-01

    The toxic effects of ethyl cinnamate on the photosynthetic and physiological characteristics of Chlorella vulgaris were studied based on chlorophyll fluorescence and flow cytometry analysis. Parameters, including biomass, F(v)/F(m) (maximal photochemical efficiency of PSII), Ф(PSII) (actual photochemical efficiency of PSII in the light), FDA, and PI staining fluorescence, were measured. The results showed the following: (1) The inhibition on biomass increased as the exposure concentration increased. 1 mg/L ethyl cinnamate was sufficient to reduce the total biomass of C. vulgaris. The 48-h and 72-h EC50 values were 2.07 mg/L (1.94-2.20) and 1.89 mg/L (1.82-1.97). (2) After 24 h of exposure to 2-4 mg/L ethyl cinnamate, the photosynthesis of C. vulgaris almost ceased, manifesting in Ф(PSII) being close to zero. After 72 h of exposure to 4 mg/L ethyl cinnamate, the Fv /Fm of C. vulgaris dropped to zero. (3) Ethyl cinnamate also affected the cellular physiology of C. vulgaris, but these effects resulted in the inhibition of cell yield rather than cell death. Exposure to ethyl cinnamate resulted in decreased esterase activities in C. vulgaris, increased average cell size, and altered intensities of chlorophyll a fluorescence. Overall, esterase activity was the most sensitive variable.

  20. Toxic Effects of Ethyl Cinnamate on the Photosynthesis and Physiological Characteristics of Chlorella vulgaris Based on Chlorophyll Fluorescence and Flow Cytometry Analysis

    Directory of Open Access Journals (Sweden)

    Yang Jiao

    2015-01-01

    Full Text Available The toxic effects of ethyl cinnamate on the photosynthetic and physiological characteristics of Chlorella vulgaris were studied based on chlorophyll fluorescence and flow cytometry analysis. Parameters, including biomass, Fv/Fm (maximal photochemical efficiency of PSII, ФPSII (actual photochemical efficiency of PSII in the light, FDA, and PI staining fluorescence, were measured. The results showed the following: (1 The inhibition on biomass increased as the exposure concentration increased. 1 mg/L ethyl cinnamate was sufficient to reduce the total biomass of C. vulgaris. The 48-h and 72-h EC50 values were 2.07 mg/L (1.94–2.20 and 1.89 mg/L (1.82–1.97. (2 After 24 h of exposure to 2–4 mg/L ethyl cinnamate, the photosynthesis of C. vulgaris almost ceased, manifesting in ФPSII being close to zero. After 72 h of exposure to 4 mg/L ethyl cinnamate, the Fv/Fm of C. vulgaris dropped to zero. (3 Ethyl cinnamate also affected the cellular physiology of C. vulgaris, but these effects resulted in the inhibition of cell yield rather than cell death. Exposure to ethyl cinnamate resulted in decreased esterase activities in C. vulgaris, increased average cell size, and altered intensities of chlorophyll a fluorescence. Overall, esterase activity was the most sensitive variable.

  1. A field study on solar-induced chlorophyll fluorescence and pigment parameters along a vertical canopy gradient of four tree species in an urban environment.

    Science.gov (United States)

    Van Wittenberghe, Shari; Alonso, Luis; Verrelst, Jochem; Hermans, Inge; Valcke, Roland; Veroustraete, Frank; Moreno, José; Samson, Roeland

    2014-01-01

    To better understand the potential uses of vegetation indices based on the sun-induced upward and downward chlorophyll fluorescence at leaf and at canopy scales, a field study was carried out in the city of Valencia (Spain). Fluorescence yield (FY) indices were derived for trees at different traffic intensity locations and at three canopy heights. This allowed investigating within-tree and between-tree variations of FY indices for four tree species. Several FY indices showed a significant (p alba (white mulberry) and Phoenix canariensis (Canary Island date palm). The upward FY parameters of M. alba, and the upward to downward ratios at 687 and 741 nm for both species, were significantly related to tree location. It was found that not the total chlorophyll (Chl) content, but rather the Chl a/b ratio showed the strongest correlations with several of the indices applied. Chl a/b was lowest at the bottom level of the highest traffic intensity location for both species due to an increased Chl b, indicating a larger light harvesting complex related to Photosystem II (LHCII) as a response to limiting light. The leaf deposits from traffic observed at this sampling location possibly led to a shading effect, resulting further in an adaptive response of the photosynthetic system and subsequent difference of FY indices. This study therefore indicated the importance of the size of LHCII on the fluorescence emission, observed under different traffic generated pollution conditions.

  2. Evaluation the vigour of urban green lawn grown under long-term shade conditions by the use of chlorophyll fluorescence technique

    Directory of Open Access Journals (Sweden)

    Dąbrowski Piotr

    2015-09-01

    Full Text Available Unfavorable light conditions in urban areas are one of the most important cause of inappropriate grass communities condition. The possibility to detect the plant stress caused by shade is an important element in shaping the environment. The answer to following questions: what is the ability to detect the stress caused by shade in chosen lawn varieties of Perennial ryegrass by using the chlorophyll a fluorescence (O-J-I-P test and which of tested varieties has the best properties to create grasslands in reduced light conditions is the aim of this work. Two-factor experimental micro-plot was conducted with three varieties and three different shadowing variants. Chlorophyll a fluorescence measurements were provided and were compared to leaf density. Our results explored significant difference between selected varieties in the terms of their photosynthetic apparatus adaption to light conditions. During May, all tested varieties were characterized by the rise of all fluorescence curve points under lower light intensity. The largest changes under shade conditions were noticed for the variety ‘Taya’. During next months a declining trend of photosynthetic efficiency for this variety was observed. On the basis of our results, we assume that each variety has unique threshold and needs of light intensity.

  3. Effect of Different Norms of Under-Mulch-Drip Irrigation on Diurnal Changes of Photosynthesis and Chlorophyll Fluorescence Parameter in High Yield Cotton of Xinjiang

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wang-feng; REN Li-tong; WANG Zhen-lin; LI Shao-kun; GOU Ling; YU Songlie; CAO Lian-pu

    2003-01-01

    Under-mulch-drip irrigation is an advanced irrigation technique, which combines plastic-film-covered cultivation with drip irrigation. The influence of different norms of under-mulch-drip irrigation on di-urnal changes of photosynthetic rates and chlorophyll fluorescence parameters of cotton was studied, in orderto understand the physiological mechanisms of water-saving and high-yielding farming in Xinjiang. Results in-dicated that limited drip irrigation, which supplies 2/3 of 375 m3 ha-1 , the widely-used irrigation norm in cot-ton cultivation in Xinjiang, caused a water deficit in cotton field. Compared with the proper drip irrigation,the leaf photosynthetic rate under limited drip irrigation decreased during 9:00 to 11:00 a. m., and was sig-nificantly suppressed at midday, and then recovered afterwards. Using the chlorophyll fluorescence method,the absorption, transfer and transformation features of solar radiation by cotton leaf were investigated. Underlimited drip irrigation, the variable fluorescence (Fy) and primary light transfer efficiency of PSII (Fv/Fm)in cotton leaves were reduced because of the high light intensities and high temperatures at noon, and the de-crease in Xinluzao8 was greater than that in Xinluzao6. Therefore, it could be concluded that Xinluzao6 has ahigher drought-tolerance, and the Fv/Fm ratio could be used as a drought-resistance index for cotton.

  4. Long-wavelength chlorophylls in photosystem I of cyanobacteria: origin, localization, and functions.

    Science.gov (United States)

    Karapetyan, N V; Bolychevtseva, Yu V; Yurina, N P; Terekhova, I V; Shubin, V V; Brecht, M

    2014-03-01

    The structural organization of photosystem I (PSI) complexes in cyanobacteria and the origin of the PSI antenna long-wavelength chlorophylls and their role in energy migration, charge separation, and dissipation of excess absorbed energy are discussed. The PSI complex in cyanobacterial membranes is organized preferentially as a trimer with the core antenna enriched with long-wavelength chlorophylls. The contents of long-wavelength chlorophylls and their spectral characteristics in PSI trimers and monomers are species-specific. Chlorophyll aggregates in PSI antenna are potential candidates for the role of the long-wavelength chlorophylls. The red-most chlorophylls in PSI trimers of the cyanobacteria Arthrospira platensis and Thermosynechococcus elongatus can be formed as a result of interaction of pigments peripherally localized on different monomeric complexes within the PSI trimers. Long-wavelength chlorophylls affect weakly energy equilibration within the heterogeneous PSI antenna, but they significantly delay energy trapping by P700. When the reaction center is open, energy absorbed by long-wavelength chlorophylls migrates to P700 at physiological temperatures, causing its oxidation. When the PSI reaction center is closed, the P700 cation radical or P700 triplet state (depending on the P700 redox state and the PSI acceptor side cofactors) efficiently quench the fluorescence of the long-wavelength chlorophylls of PSI and thus protect the complex against photodestruction.

  5. 小球藻内叶绿素a荧光特征的研究%Fluorescence Characteristics Studies of Chlorophyll a in Chlorella vulgaris

    Institute of Scientific and Technical Information of China (English)

    王志勤

    2012-01-01

    由于叶绿素a外环境极性的不同,其荧光行为有很大的改变。通过小球藻体内叶绿素荧光光谱特性的研究,发现其体内叶绿素的激发波长有在丙酮溶剂中的相同,均为430nm,但发射波长为680nm,红移了13nm。利用小球藻的叶绿素荧光强度进行水体中叶绿素a的定量检测,在浓度为1—100μg/L的浓度范围内,相对荧光强度与叶绿素浓度有很好的相关性,线性方程为Y=0.5338x+1.8515,线性相关系数R2为0.9974。%The fluorescence characteristics of Chlorophyll a were found to have great change under different polar environment. For the Chlorophyll a in Chlorella vulgaris, its excite wavelength was kept at 430 nm, but 13 nm red-shift was found for its emission wavelength. The fluorescence intensity of Chlorella vulgaris was used for the determination of Chlorophyll a in water, indicating that the response fluorescence intensity and the concentration presented a good linearity in the range of 1 to 100 μg/L, and the linear equation was y = 0.5338x + 1.8515, R2 = 0.9947.

  6. Global Monitoring of Terrestrial Chlorophyll Fluorescence from Moderate-spectral-resolution Near-infrared Satellite Measurements: Methodology, Simulations, and Application to GOME-2

    Science.gov (United States)

    Joiner, J.; Gaunter, L.; Lindstrot, R.; Voigt, M.; Vasilkov, A. P.; Middleton, E. M.; Huemmrich, K. F.; Yoshida, Y.; Frankenberg, C.

    2013-01-01

    Globally mapped terrestrial chlorophyll fluorescence retrievals are of high interest because they can provide information on the functional status of vegetation including light-use efficiency and global primary productivity that can be used for global carbon cycle modeling and agricultural applications. Previous satellite retrievals of fluorescence have relied solely upon the filling-in of solar Fraunhofer lines that are not significantly affected by atmospheric absorption. Although these measurements provide near-global coverage on a monthly basis, they suffer from relatively low precision and sparse spatial sampling. Here, we describe a new methodology to retrieve global far-red fluorescence information; we use hyperspectral data with a simplified radiative transfer model to disentangle the spectral signatures of three basic components: atmospheric absorption, surface reflectance, and fluorescence radiance. An empirically based principal component analysis approach is employed, primarily using cloudy data over ocean, to model and solve for the atmospheric absorption. Through detailed simulations, we demonstrate the feasibility of the approach and show that moderate-spectral-resolution measurements with a relatively high signal-to-noise ratio can be used to retrieve far-red fluorescence information with good precision and accuracy. The method is then applied to data from the Global Ozone Monitoring Instrument 2 (GOME-2). The GOME-2 fluorescence retrievals display similar spatial structure as compared with those from a simpler technique applied to the Greenhouse gases Observing SATellite (GOSAT). GOME-2 enables global mapping of far-red fluorescence with higher precision over smaller spatial and temporal scales than is possible with GOSAT. Near-global coverage is provided within a few days. We are able to show clearly for the first time physically plausible variations in fluorescence over the course of a single month at a spatial resolution of 0.5 deg × 0.5 deg

  7. Electric-Field-Induced Fluorescence Quenching in Polyfluorene, Ladder-Type Polymers, and MEH-PPV Evidence for Field Effects on Internal Conversion Rates in the Low Concentration Limit

    NARCIS (Netherlands)

    Moscatelli, Alberto; Livingston, Kathryn; So, Woong Young; Lee, Suk Jun; Scherf, Ullrich; Wildeman, Jurjen; Peteanu, Linda A.

    2010-01-01

    Electric field-induced fluorescence quenching has been measured for a series of conjugated polymers with applications in organic light-emitting diodes Electrofluorescence measurements on isolated chains in a glassy matrix at 77 K show that the quenching efficiency for poly[2-methoxy-5-(2-ethylhexylo

  8. Fluorescence Quenching of CdSe/ZnS Quantum Dots by Using Black Hole Quencher Molecules Intermediated With Peptide for Biosensing Application.

    Science.gov (United States)

    Pillai, Sreenadh Sasidharan; Yukawa, Hiroshi; Onoshima, Daisuke; Biju, Vasudevanpillai; Baba, Yoshinobu

    2015-12-17

    Quantum dots (QDs) have recently been investigated as fluorescent probes for detecting a very small number of biomolecules and live cells; however, the establishment of molecular imaging technology with on-off control of QD fluorescence remains to be established. Here we have achieved the fluorescence off state of QDs with the conjugation of black hole quencher (BHQ) molecules intermediated with peptide by using streptavidin-QDs585 and biotin-pep-BHQ-1. The fluorescence of streptavidin-QDs585 was decreased by the addition of biotin-pep-BHQ-1 in a dose-dependent manner. It has been suggested that the decrease in QDs585 fluorescence occurred through a Förster resonance energy transfer (FRET) mechanism from the analysis of fluorescence intensity and lifetime of streptavidin-QDs585 and QDs585-pep-BHQ-1. QDs585 fluorescence could be quenched by more than 60% efficiency in this system. The sequence of intermediate peptide (pep) was GPLGVRGK, which can be cleaved by matrix metalloproteinases (MMPs) produced by cancer cells. QDs585-pep-BHQ-1 is thus expected to detect the MMP production by the recovery of QDs585 fluorescence as a new bioanalytical agent for molecular imaging.

  9. Deep two-photon microscopic imaging through brain tissue using the second singlet state from fluorescent agent chlorophyll α in spinach leaf.

    Science.gov (United States)

    Shi, Lingyan; Rodríguez-Contreras, Adrián; Budansky, Yury; Pu, Yang; Nguyen, Thien An; Alfano, Robert R

    2014-06-01

    Two-photon (2P) excitation of the second singlet (S₂) state was studied to achieve deep optical microscopic imaging in brain tissue when both the excitation (800 nm) and emission (685 nm) wavelengths lie in the "tissue optical window" (650 to 950 nm). S₂ state technique was used to investigate chlorophyll α (Chl α) fluorescence inside a spinach leaf under a thick layer of freshly sliced rat brain tissue in combination with 2P microscopic imaging. Strong emission at the peak wavelength of 685 nm under the 2P S₂ state of Chl α enabled the imaging depth up to 450 μm through rat brain tissue.

  10. Diurnal variations in gas exchange and chlorophyll fluorescence in rice leaves: the cause for midday depression in CO2 photosynthetic rate

    Directory of Open Access Journals (Sweden)

    Debabrata Panda

    2011-12-01

    Full Text Available Gas exchange and chlorophyll fluorescence analysis were carried out to investigate the diurnal variations in photosynthesis in leaves of rice (Oryza sativa L.. Leaf CO2 photosynthetic rate (Pn showed a bimodal diurnal pattern and midday depression in Pn was observed at 13:00 h. Depression in Pn at midday was mostly attributed to stomatal limitation since the reduction in Pn was followed by the significant reduction in stomatal conductance (Gs. Midday depression in Pn was found to be associated with reversible inactivation of Photo-system II (PS II reaction centers and increase of photo-inhibition in response to high intensity as evidenced by the maximum efficiency of PS II (Fv/Fm decreased with increase of light intensity from 6:00 h to 16:00 h of a day. The minimal fluorescence (Fo gradually increased with increasing light intensity and reached its highest value at 13:00 h and on contrary the maximal fluorescence (Fm decreased and reached its lowest value at 13:00 h. Quantification of several chlorophyll fluorescence parameters (JIP-test like area above the fluorescence curve between Fo and Fm, phenomenological energy fluxes like electron transport per cross section (ETo/CS, active PS II reaction center per exited cross-section (RC/CSo and performance index (Pi were low in early morning, increasing with time and reaching a maximum at 9:00 h subsequently decreasing and reaching a minimum value at 13.00 h. On contrary the dissipation per cross-section (Dio/CS gradually increased with increasing light intensity and reached its highest value at 13:00 h. It is likely that PS II down-regulation and heat dissipation co-operated together to prevent the chloroplast from photo damage.

  11. Preliminary Studies on chlorophyll fluorescence characteristics of endangered plant Ulmus elongata seedlings%濒危植物长序榆(Ulmus elongata)幼苗叶绿素荧光特性的初步研究

    Institute of Scientific and Technical Information of China (English)

    高建国; 徐根娣; 刘鹏; 岑维亚

    2011-01-01

    用Li-6400XT便携式光合作用仪对濒危植物长序榆幼苗的各叶绿素荧光参数的日变化和快速光响应曲线进行了测定.结果发现,光系统Ⅱ(PSⅡ)的实际光化学效率(ΦPS Ⅱ)、电子传递速率(ETR)在整个白天阶段较稳定,下午18:00显著下降.光化学淬灭(qP)先增大后减小.非光化学淬灭(NPQ)呈现出与光化学淬灭(qP)相反的变化趋势,中午最低,说明长序榆幼苗光能利用率较高.快速光曲线表明实际光化学效率(ΦPSⅡ)和光化学淬灭(qP)随着光合有效辐射(PAR)的增大而减小,电子传递速率(ETR)和非光化学淬灭(NPQ)随着光合有效辐射(PAR)的增大而增大.使用幂函数能够很好的拟合实际光化学效率(ΦPSⅡ)和电子传递速率(ETR)随光强的变化,而对数函数能较好的拟合实际光化学淬灭(qP)和非光化学淬灭(NPQ)随光强的变化.%Diurnal variations of chlorophyll fluorescence parameters and rapid light curves of endangered plant Ulmus elongata seedlings were determined by using Li -6400XT portable photosynthesis system. The results showed that the actual photochemical efficiency(ΦPSII)> electron transport rate(ETR)of photosystem H(PSII)were stable throughout the daytime, and decreased significantly at 18:00 pm. Photochemical quenching (qP)increased firstly at morning and then decreased after midday, non-photochemical quenching (NPQ)showed the opposite changes, the minimum at noon, indicating that the light use efficiency of Ulmus elongata seedlings were high. The rapid light curves showed that actual photochemical efficiency(ΦPSII) and photochemical quenching (qP)decreased while the photosynthetic active radiation (PAR)increased, electron transport rate (ETR)and non-photochemical quenching (NPQ)increased while the photosynthetic active radiation (PAR)increased. The power function could fit well the actual photochemical efficiency (ΦPSII)and electron transport rate (ETR)with the light intensity changes, while

  12. Photosystem II antennae are not energetically connected: evidence based on flash-induced O2 evolution and chlorophyll fluorescence in sunflower leaves.

    Science.gov (United States)

    Oja, Vello; Laisk, Agu

    2012-10-01

    Oxygen evolution was measured in sunflower leaves in steady-state and during multiple-turnover pulses (MTP) of different light (630 nm LED plus far-red light) intensity and duration. In parallel, Chl fluorescence yields F(0) (minimum), F(s) (steady-state), and F(m) (pulse-saturated), as well as fluorescence induction during MTPs were recorded. Extra O(2) evolution was measured in response to a saturating single-turnover Xe flash (STF) applied immediately subsequently to the actinic light in the steady-state and to each MTP. Under the used anaerobic conditions and randomized S-states electron transport per STF was calculated as 4O(2) evolution. The STF-induced electron transport (=the number of open PSII) was maximal at the low background light, but decreased with progressing light saturation in steady-state and with the increasing duration of MTP. The quantum yield (effective antenna size) of open PSII centers remained constant when adjacent centers became closed. The photochemical quenching of fluorescence q(P) = (F(m) - F(s))/(F(m) - F(0)) was proportional with the portion of open PSII centers in the steady-state (variable non-photochemical quenching, NPQ) and with increasing MTP duration (NPQ absent). Comparison of experimental responses to a model based on PSII dimers with well-connected antennae showed no energetic connectivity between PSII antennae in intact leaves, suggesting that in vivo PSII exist as monomers, or dimers with energetically disconnected antennae.

  13. Chlorophyll a Fluorescence as a Tool in Evaluating the Effects of ABA Content and Ethylene Inhibitors on Quality of Flowering Potted Bougainvillea

    Directory of Open Access Journals (Sweden)

    Antonio Ferrante

    2012-01-01

    Full Text Available Flowering potted plants during the postproduction stage are usually stored in inadequate environmental conditions. We evaluated the effect of the most common storage conditions and treatments on two Bougainvillea cultivars after harvest and during recovery. Flowering potted Bougainvillea plants were treated with 100 mL 2 mM amino-oxyacetic acid (AOA or 500 ppb 1-methylcyclopropene (1-MCP prior storage in dark at 14∘C for simulating transport or storage conditions and, subsequently, transferred to growth chambers at 20∘C in the light for one week for evaluating the recovery ability. The plant stress during the experiments was assessed by ethylene, ABA, and chlorophyll a fluorescence measurements. Ethylene production was affected by temperature rather than treatments. ABA concentration declined in leaves and flowers during storage and was not affected by treatments. Fluorescence parameters appear to be very useful for screening Bougainvillea cultivars resistant to prolonged storage periods.

  14. Chlorophyll a fluorescence as a tool in evaluating the effects of ABA content and ethylene inhibitors on quality of flowering potted Bougainvillea.

    Science.gov (United States)

    Ferrante, Antonio; Trivellini, Alice; Borghesi, Eva; Vernieri, Paolo

    2012-01-01

    Flowering potted plants during the postproduction stage are usually stored in inadequate environmental conditions. We evaluated the effect of the most common storage conditions and treatments on two Bougainvillea cultivars after harvest and during recovery. Flowering potted Bougainvillea plants were treated with 100 mL 2 mM amino-oxyacetic acid (AOA) or 500 ppb 1-methylcyclopropene (1-MCP) prior storage in dark at 14°C for simulating transport or storage conditions and, subsequently, transferred to growth chambers at 20°C in the light for one week for evaluating the recovery ability. The plant stress during the experiments was assessed by ethylene, ABA, and chlorophyll a fluorescence measurements. Ethylene production was affected by temperature rather than treatments. ABA concentration declined in leaves and flowers during storage and was not affected by treatments. Fluorescence parameters appear to be very useful for screening Bougainvillea cultivars resistant to prolonged storage periods.

  15. Detection of DNA via the fluorescence quenching of Mn-doped ZnSe D-dots/doxorubicin/DNA ternary complexes system.

    Science.gov (United States)

    Gao, Xue; Niu, Lu; Su, Xingguang

    2012-01-01

    This manuscript reports a method for the detection of double-stranded DNA, based on Mn:ZnSe d-dots and intercalating agent doxorubicin (DOX). DOX can quench the photoluminescence (PL) of Mn:ZnSe d-dots through photoinduced electron transfer process, after binding with Mn:ZnSe d-dots. The addition of DNA can result in the formation of the Mn:ZnSe d-dots-DOX-DNA ternary complexes, the fluorescence of the Mn:ZnSe d-dots-DOX complexes would be further quenched by the addition of DNA, thus allowing the detection of DNA. The formation mechanism of the Mn:ZnSe d-dots-DOX-DNA ternary complexes was studied in detail in this paper. Under optimal conditions, the quenched fluorescence intensity of Mn:ZnSe d-dots-DOX system are perfectly described by Stern-Volmer equation with the concentration of hsDNA ranging from 0.006 μg mL(-1) to 6.4 μg mL(-1). The detection limit (S/N = 3) for hsDNA is 0.5 ng mL(-1). The proposed method was successfully applied to the detection of DNA in synthetic samples and the results were satisfactory.

  16. Electron-transfer fluorescence quenching processes in coaggregates between excited N-alkylcarbazoles as electron donors and 2, 4-dinitrophenyl carboxylates or pentafiuorophenyl carboxylates as acceptors

    Institute of Scientific and Technical Information of China (English)

    SHI, Ji-Liang; YI, Hu-Nan; XU, Jia-Yi; JIANG, Xi-Kui

    2000-01-01

    Electron-transfer processes facilitated by hydrophobiclipophilic interaction (HLI) between excited N-alkylcarbazoles (1-n, n=4, 8, 12, 16) as electron donors and 2,4dinnrophenyl carboxylates (2-n, n = 4, 8, 12, 16) or pentafluorophenyl carboxylates (3-n, n = 4, 8, 12, 16) as electron acceptors have been investigated by means of fluorescence spectroscopy in aqueous or aquiorgano binary mixtures.The fluorescence quenching of-n* by2-n or-n indicates that preassociation precedes the electron transfer. The extent of HLI-drtven coaggregation of the acceptor and the donor may be assessed from the B value of the equation I0/I = A + B [Q]. The chain-length effect and possibly also a chain-foldability effect, as well as the solvent aggregating power (SAgP)effect have been observed. Comparison of the quenching constants ( B ) for 1-n* /2-n combinations and 1-n* / 3-n combinations shows that the order of increasing B values for the quenching processes is 3-n < 2-n.

  17. [Effects of long-term ozone exposure on chlorophyll a fluorescence and gas exchange of winter-wheat leaves].

    Science.gov (United States)

    Zheng, You-fei; Zhao, Ze; Wu, Rong-jun; Hu, Cheng-da; Liu, Hong-ju

    2010-02-01

    In order to provide basis for evaluating the effects of air pollutant such as O3 on crops yield and food security, the effects of O3 fumigation (ambient air, CK; 100 nL x L(-1), T1; 150 nL x L(-1), T2) on chlorophyll a fluorescence and gas exchange of a field-grown winter-wheat (Triticum aestivum L. Yang Mai 13) in different growing period were conducted via open-top chamber technique in conjunction with Diving-PAM fluorometer and LC pro + photosynthesis system. Results indicated that Fv/Fm caused by T1 was higher than 0.8, while the Pm, qP, (1-qP)/NPQ and Y(NO) were similar to those of CK, the NPQ and Y(NPQ) were increased by 13.5%-29.0% and 13.3%-22.7% respectively due to O3 stress. Under nature light (rapid light curve, RLC) and after dark adaptation (induction curve in steady-state, IC) the Yield of T1 was decreased by 4.6%-7.6% and 11.3%-19.3% respectively, with 8.0%-9.8% and 11.0%-23.1% reductions in Pn, and Gs compared to CK, respectively. In heading stage and blooming stage, the Ls of T, was greater than CK, but in filling stage and mature stage, it became lower compared to CK. The Fv/Fm was slightly lower than 0.8 under T2 treatment, with the Y(NO), (1-qP)/NPQ and c(i) were increased by 37.9%-75.6%, 157.1%-325.8% and 3.4%-18.1% relative to CK. Under RLC and IC condition, the Yield of T2 was respectively decreased by 10.2%-13.6% and 21.4%-29.1%, and the Pn, Ls, qP, Pm, NPQ and Y(NPQ) were decreased by 28.1%-39.9%, 5.2%-21.3%, 15.8%-30.4%, 27.6%-45.6%, 3.3%-52.9% and 5.7%-17.9% in comparison, respectively. Obviously the enhanced O3 causes a significant decrease in the capacity of photosynthesis of winter wheat, and the influence mechanism presents a series of dynamic changes according to growing seasons. The reduction of Fv/Fm under T1 treatment is a response of PS II reaction center to the increase of NPQ, and the decrease in Pn and Yield is a consequence of protective adjustment, by this approach, the antioxidant system and energy dissipation mechanism can

  18. Effects of Chilling Stress on Photosynthetic Rate and Chlorophyll Fluorescence Parameter in Seedlings of Two Rice Cultivars Differing in Cold Tolerance

    Institute of Scientific and Technical Information of China (English)

    WANG Guo-li; GUO Zhen-fei

    2005-01-01

    A cold-tolerant cultivar, Xiangnuo 1, and a cold-sensitive cultivar, IR50, were used to study the influence of chilling on photosynthetic rate and chlorophyll fluorescence parameters in rice seedlings. The photosynthetic rates declined dramatically during chilling, and decreased by 48.7% and 67.5% in Xiangnuo 1 and IR50 seedlings, respectively, after being subjected to chilling treatment for two days. Chlorophyll fluorescence measurements showed that relatively higher qP and qNP in Xiangnuo 1 were maintained to dissipate the redundant excitation energy and protect the reaction centers from chill injury; accordingly, redundant excitation energy accumulated less in the reaction centers, and antenna systems were less injured by chilling in Xiangnuo 1. On the contrary, in IR50, qP and qNP declined rapidly while Ex increased, as the chilling persisted. This result indicated that the reaction centers and antenna systems in IR50 were damaged severely by chilling, which led to the lower photosynthetic rate.

  19. Spectroscopic properties of chlorophyll f.

    Science.gov (United States)

    Li, Yaqiong; Cai, Zheng-Li; Chen, Min

    2013-09-26

    The absorption and fluorescence spectra of chlorophyll f (newly discovered in 2010) have been measured in acetone and methanol at different temperatures. The spectral analysis and assignment are compared with the spectra of chlorophyll a and d under the same experimental conditions. The spectroscopic properties of these chlorophylls have further been studied by the aid of density functional CAM-B3LYP and high-level symmetric adapted coupled-cluster configuration interaction calculations. The main Q and Soret bands and possible sidebands of chlorophylls have been determined. The photophysical properties of chlorophyll f are discussed.

  20. Effects of foliar spraying methyl jasmonate on leaf chlorophyll fluorescence characteristics of flue-cured tobacco seedlings under drought and re-watering%茉莉酸甲酯对干旱及复水条件下烤烟幼苗叶绿素荧光特性的影响

    Institute of Scientific and Technical Information of China (English)

    金微微; 王炎; 张会慧; 焦志丽; 王鹏; 李鑫; 岳冰冰; 孙广玉

    2011-01-01

    以烤烟品种“龙江911”为试验材料,研究了干旱及复水过程中外源茉莉酸甲酯(Me-JA)对移栽后烤烟幼苗叶绿素含量和叶绿素荧光特性的影响.结果表明:干旱下烤烟幼苗叶绿素含量、PSⅡ反应中心完全关闭时荧光产量(Fm)、PSⅡ潜在活性(Fv/Fo)、最大光化学效率(Fv/Fm)、实际光化学效率(φPSⅡ)、表观电子传递速率(ETR)和光化学猝灭系数(qp)下降,而初始荧光(Fo)和非光化学猝灭系数(qN)升高,0.2和0.5 mmol·L-1的外源MeJA明显减缓了干旱下烤烟幼苗Fv/Fm、Fv /Fo、φPsⅡ、ETR、qP的下降和qN的上升,而1.0 mmol·L-1 MeJA效果不明显.复水后,烤烟幼苗各项叶绿素荧光指标均有明显恢复,并且MeJA处理后的幼苗恢复更明显.表明外源MeJA减轻了干旱胁迫下烤烟叶片叶绿素的分解,对PSⅡ反应中心起到一定的保护作用,提高了电子传递速率,降低了干旱胁迫对烤烟幼苗的伤害,并且复水后叶绿素含量和叶绿素荧光参数能迅速恢复,从而保证了经干旱胁迫后烤烟幼苗能迅速缓苗.%Taking the flue-cured tobacco variety of "Longjiang 911" from Heilongjiang Province of Northeast China as test material, a pot experiment was conducted to study the effects of foliar spraying different concentration methyl jasmonate ( MeJA) on the seedlings leaf chlorophyll content and chlorophyll fluorescence characteristics during the transplantation stage under drought and re-watering. Under drought condition, the leaf chlorophyll content, maximum fluorescence ( Fm ) , potential activities of PSII (Fv/Fo) , maximum photochemical efficiency ( Fv/Fm ) , actual photochemical efficiency ( φpsⅡ ) , apparent electron transport rate (ETR), and photochemical quenching ( qp) decreased, but the minimal fluorescence ( Fo) and non-photochemical quenching ( qN ) increased. Foliar spraying 0. 2 and 0. 5 mmol · L-1 of MeJA had obvious positive effects in mitigating the decrease of Fv/Fm, Fv

  1. Effect of Different Light Qualities on Growth, Pigment Content, Chlorophyll Fluorescence, and Antioxidant Enzyme Activity in the Red Alga Pyropia haitanensis (Bangiales, Rhodophyta)

    Science.gov (United States)

    2016-01-01

    Spectral light changes evoke different morphogenetic and photosynthetic responses that can vary among different algae species. The aim of this study is to investigate the photosynthetic characteristics of the red macroalgae grown under different spectrum environments. In this study, Pyropia haitanensis were cultured under blue, red, and green LED and fluorescent tubes light. The growth rate, photopigment composition, chlorophyll fluorescence, and antioxidative enzymes activities in different light spectrums were investigated. The results revealed that growth rate was significantly higher in the thalli grown under blue, green, and fluorescent tubes light. Contents of Chl a and phycobiliprotein in red light were lower among all the growth conditions. Furthermore, a striking increase in SOD and CAT activity was observed in red light treatment along with the NPQ increase. The results revealed that the photosynthetic efficiency and increased growth rate of P. haitanensis benefitted from light spectrums such as blue, green, and fluorescent tubes light by pigment composition and photochemical efficiency manipulation, whereas red light has disadvantageous effects. Accordingly, the results for improving quality and the economic yield of algae species in some extent and the combination of different wavelengths could allow better economic resource exploitation. PMID:27642603

  2. Effect of Different Light Qualities on Growth, Pigment Content, Chlorophyll Fluorescence, and Antioxidant Enzyme Activity in the Red Alga Pyropia haitanensis (Bangiales, Rhodophyta

    Directory of Open Access Journals (Sweden)

    Huanyang Wu

    2016-01-01

    Full Text Available Spectral light changes evoke different morphogenetic and photosynthetic responses that can vary among different algae species. The aim of this study is to investigate the photosynthetic characteristics of the red macroalgae grown under different spectrum environments. In this study, Pyropia haitanensis were cultured under blue, red, and green LED and fluorescent tubes light. The growth rate, photopigment composition, chlorophyll fluorescence, and antioxidative enzymes activities in different light spectrums were investigated. The results revealed that growth rate was significantly higher in the thalli grown under blue, green, and fluorescent tubes light. Contents of Chl a and phycobiliprotein in red light were lower among all the growth conditions. Furthermore, a striking increase in SOD and CAT activity was observed in red light treatment along with the NPQ increase. The results revealed that the photosynthetic efficiency and increased growth rate of P. haitanensis benefitted from light spectrums such as blue, green, and fluorescent tubes light by pigment composition and photochemical efficiency manipulation, whereas red light has disadvantageous effects. Accordingly, the results for improving quality and the economic yield of algae species in some extent and the combination of different wavelengths could allow better economic resource exploitation.

  3. Design and daytime performance of laser-induced fluorescence spectrum lidar for simultaneous detection of multiple components, dissolved organic matter, phycocyanin, and chlorophyll in river water.

    Science.gov (United States)

    Saito, Yasunori; Kakuda, Kei; Yokoyama, Mizuho; Kubota, Tomoki; Tomida, Takayuki; Park, Ho-Dong

    2016-08-20

    In this work, we developed mobile laser-induced fluorescence spectrum (LIFS) lidar based on preliminary experiments on the excitation emission matrix of a water sample and a method for reducing solar background light using the synchronous detection technique. The combination of a UV short-pulse laser (355 nm, 6 ns) for fluorescence excitation with a 10-100 ns short-time synchronous detection using a gated image-intensified multi-channel CCD of the fluorescence made the LIFS lidar operation possible even in daytime. The LIFS lidar with this construction demonstrated the potential of natural river/lake water quality monitoring at the Tenryu River/Lake Suwa. Three main components in the fluorescence data of the water, dissolved organic matter, phycocyanin, and chlorophyll, were extracted by spectral analysis using the standard spectral functions of these components. Their concentrations were estimated by adapting experimentally calibrated data. Results of long-term field observations using our LIFS lidar from 2010 to 2012 show the necessity of simultaneous multi-component detection to understand the natural water environment.

  4. Vase Life Extension and Chlorophyll Fluorescence Yield of Bougainvillea Flower as Influenced by Ethanol to Attain Maximum Environmental Beautification as Ornamental Components

    Directory of Open Access Journals (Sweden)

    A. B.M. Hossain

    2008-01-01

    Full Text Available The study was conducted to investigate the effect of ethanol at different concentrations (ET on bougainvillea flower longevity and delay senescence in storage condition. The treatments were water control, 2% ET, 4% ET, 8% ET, 10% ET, 20% ET, 30% ET, 40% ET, 50% ET and 70% ET. Flower longevity was 2 days more in 4, 8% and 10% ethanol than water control and other concentrations of ethanol. Petal wilting and senescence were occurred 2 days later in 4, 8 and 10% ET than in water control. Percent petal's color changed was later in water 4, 8% and 10% than in control,