Instrumentation in Developing Chlorophyll Fluorescence Biosensing: A Review

Science.gov (United States)

Fernandez-Jaramillo, Arturo A.; Duarte-Galvan, Carlos; Contreras-Medina, Luis M.; Torres-Pacheco, Irineo; de J. Romero-Troncoso, Rene; Guevara-Gonzalez, Ramon G.; Millan-Almaraz, Jesus R.

2012-01-01

Chlorophyll fluorescence can be defined as the red and far-red light emitted by photosynthetic tissue when it is excited by a light source. This is an important phenomenon which permits investigators to obtain important information about the state of health of a photosynthetic sample. This article reviews the current state of the art knowledge regarding the design of new chlorophyll fluorescence sensing systems, providing appropriate information about processes, instrumentation and electronic devices. These types of systems and applications can be created to determine both comfort conditions and current problems within a given subject. The procedure to measure chlorophyll fluorescence is commonly split into two main parts; the first involves chlorophyll excitation, for which there are passive or active methods. The second part of the procedure is to closely measure the chlorophyll fluorescence response with specialized instrumentation systems. Such systems utilize several methods, each with different characteristics regarding to cost, resolution, ease of processing or portability. These methods for the most part include cameras, photodiodes and satellite images. PMID:23112686

Instrumentation in Developing Chlorophyll Fluorescence Biosensing: A Review

Directory of Open Access Journals (Sweden)

Jesus R. Millan-Almaraz

2012-08-01

Full Text Available Chlorophyll fluorescence can be defined as the red and far-red light emitted by photosynthetic tissue when it is excited by a light source. This is an important phenomenon which permits investigators to obtain important information about the state of health of a photosynthetic sample. This article reviews the current state of the art knowledge regarding the design of new chlorophyll fluorescence sensing systems, providing appropriate information about processes, instrumentation and electronic devices. These types of systems and applications can be created to determine both comfort conditions and current problems within a given subject. The procedure to measure chlorophyll fluorescence is commonly split into two main parts; the first involves chlorophyll excitation, for which there are passive or active methods. The second part of the procedure is to closely measure the chlorophyll fluorescence response with specialized instrumentation systems. Such systems utilize several methods, each with different characteristics regarding to cost, resolution, ease of processing or portability. These methods for the most part include cameras, photodiodes and satellite images.

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.

Chlorophyll Fluorescence Imaging Uncovers Photosynthetic Fingerprint of Citrus Huanglongbing

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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.

Acute toxicity of excess mercury on the photosynthetic performance of cyanobacterium, S. platensis--assessment by chlorophyll fluorescence analysis.

Science.gov (United States)

Lu, C M; Chau, C W; Zhang, J H

2000-07-01

Measurement of chlorophyll fluorescence has been shown to be a rapid, non-invasive, and reliable method to assess photosynthetic performance in a changing environment. In this study, acute toxicity of excess Hg on the photosynthetic performance of the cyanobacterium S. platensis, was investigated by use of chlorophyll fluorescence analysis after cells were exposed to excess Hg (up to 20 microM) for 2 h. The results determined from the fast fluorescence kinetics showed that Hg induced a significant increase in the proportion of the Q(B)-non-reducing PSII reaction centers. The fluorescence parameters measured under the steady state of photosynthesis demonstrated that the increase of Hg concentration led to a decrease in the maximal efficiency of PSII photochemistry, the efficiency of excitation energy capture by the open PSII reaction centers, and the quantum yield of PSII electron transport. Mercury also resulted in a decrease in the coefficients of photochemical and non-photochemical quenching. Mercury may have an acute toxicity on cyanobacteria by inhibiting the quantum yield of photosynthesis sensitively and rapidly. Such changes occurred before any other visible damages that may be evaluated by other conventional measurements. Our results also demonstrated that chlorophyll fluorescence analysis can be used as a useful physiological tool to assess early stages of change in photosynthetic performance of algae in response to heavy metal pollution.

Detecting crop population growth using chlorophyll fluorescence imaging.

Science.gov (United States)

Wang, Heng; Qian, Xiangjie; Zhang, Lan; Xu, Sailong; Li, Haifeng; Xia, Xiaojian; Dai, Liankui; Xu, Liang; Yu, Jingquan; Liu, Xu

2017-12-10

For both field and greenhouse crops, it is challenging to evaluate their growth information on a large area over a long time. In this work, we developed a chlorophyll fluorescence imaging-based system for crop population growth information detection. Modular design was used to make the system provide high-intensity uniform illumination. This system can perform modulated chlorophyll fluorescence induction kinetics measurement and chlorophyll fluorescence parameter imaging over a large area of up to 45  cm×34  cm. The system can provide different lighting intensity by modulating the duty cycle of its control signal. Results of continuous monitoring of cucumbers in nitrogen deficiency show the system can reduce the judge error of crop physiological status and improve monitoring efficiency. Meanwhile, the system is promising in high throughput application scenarios.

Vegetation Function and Physiology: Photosynthesis, Fluorescence and Non-photochemical Quenching (NPQ)

Science.gov (United States)

Zhang, Q.; Yao, T.

2017-12-01

Photosynthesis is a basic physiological function of vegetation that relies on PAR provided through photosynthetic pigments (mainly chlorophyll) for plant growth and biomass accumulation. Vegetation chlorophyll (chl) content and non-chlorophyll (non-chl) components vary with plant functional types (PFTs) and growing stages. The PAR absorbed by canopy chlorophyll (APARchl) is associated with photosynthesis (i.e., gross primary production, GPP) while the PAR absorbed by canopy non-chl components (APARnon-chl) is not associated with photosynthesis. Under non-optimal environmental conditions, vegetation is "stressed" and both photosynthesis (GPP) and light use efficiency are reduced, therefore, excess portions of APARchl are discarded as fluorescence or non-photochemical quenching (NPQ). The photochemical reflectance index (PRI) is a measurement related to NPQ. Both PRI and yield of solar induced chlorophyll fluorescence (SIFyield = SIF/APARchl) have been proposed as possible bio-indicators of LUEchl. We have successfully developed an algorithm to distinguish between chlorophyll and non-chl components of vegetation, and to retrieve fractional absorptions of PAR by chlorophyll (fAPARchl) and by non-chl components (fAPARnon-chl) with surface reflectance of MODIS bands 1 - 7. A method originally pioneered by Hanan et al. (2002) has been used to retrieve fAPAR for vegetation photosynthesis (fAPARPSN) at flux tower sites based on the light response curve of tower net ecosystem exchange (NEE) and incident PAR at low light intensity. We have also retrieved the PRI from MODIS data (bands 11 and 1) and have derived SIFyield with the Global Ozone Monitoring Experiment - 2 (GOME-2) SIF data. We find that fAPARPSN at flux tower sites matches well with site fAPARchl, and ratio fAPARnon-chl/fAPARchl varies largely. APARchl can explain >=78% variation in seasonal GPP . We disentangle the possible impact of fAPARchl on PRI from physiological stress response, disentangle the possible

Detection of photosynthetic performance of Stipa bungeana seedlings under climatic change using chlorophyll fluorescence imaging

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Xiliang eSong

2016-01-01

Full Text Available In this study, the impact of future climate change on photosynthetic efficiency as well as energy partitioning in the Stipa bungeana was investigated by using chlorophyll fluorescence imaging (CFI technique. Two thermal regimes (room temperature, T0: 23.0/17.0℃; High temperature, T6: 29.0/23.0℃ and three water conditions (Control, W0; Water deficit, W-30; excess precipitation, W+30 were set up in artificial control chambers. The results showed that excess precipitation had no significant effect on chlorophyll fluorescence parameters, while water deficit decreased the maximal quantum yield of photosystem II (PSII photochemistry for the dark-adapted state (Fv/Fm by 16.7%, with no large change in maximal quantum yield of PSII photochemistry for the light-adapted state (FV'/FM' and coefficient of the photochemical quenching (qP at T0 condition. Under T6 condition, high temperature offset the negative effect of water deficit on Fv/Fm and enhanced the positive effect of excess precipitation on Fv/Fm, Fv'/Fm' and qP, the values of which all increased. This indicates that the temperature higher by 6 ℃ will be beneficial to the photosynthetic performance of S. bungeana. Spatial changes of photosynthetic performance were monitored in three areas of interest (AOIs located on the bottom, middle and upper position of leaf. Chlorophyll fluorescence images (Fv/Fm, actual quantum yield of PSII photochemistry for the light-adapted state (ΦPSII, quantum yield of nonregulated energy dissipation for the light-adapted state (ΦNO at T0 condition, and ΦPSII at T6 condition showed a large spatial variation, with greater value of ΦNO and lower values of Fv/Fm and ΦPSII in the upper position of leaves. Moreover, there was a closer relationship between ΦPSII and ΦNO, suggesting that the energy dissipation by non-regulated quenching mechanisms played a dominant role in the yield of PSII photochemistry. It was also found that, among all measured fluorescence

Fluorescence quenching of Rhodamine B base by two amines

Science.gov (United States)

Bakkialakshmi, S.; Selvarani, P.; Chenthamarai, S.

2013-03-01

Fluorescence quenching of Rhodamine B base (RhB) in DMF solution has been studied at different concentrations of the amine Triethyl amine (TEA) and n-butyl amine (NBA) at room temperature. It has been observed that the fluorescence intensity of RhB decrease with increase in the concentration of the TEA and NBA. It has been observed that the quenching due to amines proceeds via dynamic quenching process. The rate constants for the quenching process have been calculated using Stern-Volmer equation. Time resolved fluorescence study and 1H NMR spectral study have also been carried out and discussed.

Near infrared fluorescent chlorophyll nanoscale liposomes for sentinel lymph node mapping

Science.gov (United States)

Fan, Lina; Wu, Qiang; Chu, Maoquan

2012-01-01

Background Sentinel lymph node (SLN) mapping using in vivo near infrared fluorescence imaging has attracted great attention during the past few years. Here we report on the early use of poorly water-soluble chlorophyll with near infrared fluorescence extracted from the leaf of Chimonanthus salicifolius, for mouse axillary SLN mapping. Methods and results To improve the water solubility and SLN targeting of the chlorophyll, we encapsulated the chlorophyll in nanoscale liposomes. The liposome-coated chlorophyll nanocomposites obtained were spherical in shape and had an average diameter of 21.7 ± 6.0 nm. The nanocomposites dispersed well in water, and in aqueous suspension they exhibited brighter near infrared fluorescence than chlorophyll alone. After incubation of the nanocomposites with normal liver cells (QSG-7701) and macrophage cells (Ana-1) for no more than 48 hours, there was no obvious reduction in cell viability. When the nanocomposites were injected intradermally into the paw of a mouse, the axillary SLN was found to be strongly fluorescent and was easily visualized in real time without a requirement for surgery. The intensity of the near infrared fluorescence emitted by the SLN was obviously brighter than that emitted by the SLN of another mouse that had been intradermally injected with chlorophyll alone. Conclusion Our data show that the liposome-coated chlorophyll nanocomposites could have great potential for clinical SLN mapping due to their lack of toxicity, bright near infrared fluorescence, and small diameter. PMID:22787402

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

Anthracene Fluorescence Quenching by a Tetrakis (Ketocarboxamide Cavitand

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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.

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. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Phenotyping of Arabidopsis Drought Stress Response Using Kinetic Chlorophyll Fluorescence and Multicolor Fluorescence Imaging

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Jieni Yao

2018-05-01

Full Text Available Plant responses to drought stress are complex due to various mechanisms of drought avoidance and tolerance to maintain growth. Traditional plant phenotyping methods are labor-intensive, time-consuming, and subjective. Plant phenotyping by integrating kinetic chlorophyll fluorescence with multicolor fluorescence imaging can acquire plant morphological, physiological, and pathological traits related to photosynthesis as well as its secondary metabolites, which will provide a new means to promote the progress of breeding for drought tolerant accessions and gain economic benefit for global agriculture production. Combination of kinetic chlorophyll fluorescence and multicolor fluorescence imaging proved to be efficient for the early detection of drought stress responses in the Arabidopsis ecotype Col-0 and one of its most affected mutants called reduced hyperosmolality-induced [Ca2+]i increase 1. Kinetic chlorophyll fluorescence curves were useful for understanding the drought tolerance mechanism of Arabidopsis. Conventional fluorescence parameters provided qualitative information related to drought stress responses in different genotypes, and the corresponding images showed spatial heterogeneities of drought stress responses within the leaf and the canopy levels. Fluorescence parameters selected by sequential forward selection presented high correlations with physiological traits but not morphological traits. The optimal fluorescence traits combined with the support vector machine resulted in good classification accuracies of 93.3 and 99.1% for classifying the control plants from the drought-stressed ones with 3 and 7 days treatments, respectively. The results demonstrated that the combination of kinetic chlorophyll fluorescence and multicolor fluorescence imaging with the machine learning technique was capable of providing comprehensive information of drought stress effects on the photosynthesis and the secondary metabolisms. It is a promising

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...... 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...... to a decrease in calcein fluorescence with high signal-to-noise ratio (>15). Similar results were obtained with the fluorophore BCECF when excited at its isosbestic wavelength (436 nm). The present results demonstrate the usefulness of fluorescence self-quenching to measure rapid changes in cell water volume....

[Effects of different water potentials on leaf gas exchange and chlorophyll fluorescence parameters of cucumber during post-flowering growth stage].

Science.gov (United States)

Lin, Lu; Tang, Yun; Zhang, Ji-tao; Yan, Wan-li; Xiao, Jian-hong; Ding, Chao; Dong, Chuan; Ji, Zeng-shun

2015-07-01

Impacts of different substrate water potentials (SWP) on leaf gas exchange and chlorophyll fluorescence parameters of greenhouse cucumber during its post-flowering growth stage were analyzed in this study. The results demonstrated that -10 and -30 kPa were the critical values for initiating stomatal and non-stomatal limitation of drought stress, respectively. During the stage of no drought stress (-10 kPa gas exchange parameters and chlorophyll fluorescence parameters were not different significantly among treatments. During the stage of stomatal limitation of drought stress (-30 kPawater use efficiency (WUEi) and non-photochemical quenching (qN) increased. In this stage, gas exchange parameters changed faster than chlorophyll fluorescence parameters and differed significantly among treatments. During the stage of non-stomatal limitation of drought stress (-45 kPa≤SWP ≤ -30 kPa), with the decrease of SWP, light saturation point (LSP), Rd, CE, Vcmax, VTPU, LS, WUEi, ΦpPSII, Fv/Fm and qp decreased, while CCP, Ci and qN increased. In this stage, chlorophyll fluorescence parameters changed faster than gas exchange parameters and differed significantly among treatments. In production of greenhouse cucumber, -10 and -5 kPa should be the lower and upper limit value of irrigation, respectively. The stomatal limitation of drought stress could be relieved by irrigation before SWP decreased to -30 kPa. While, the non-stomatal injury of drought stress would be unrecoverable once SWP decreased to lower than -30 kPa.

A fluorescence quenching test for the detection of flavonoid transformation.

Science.gov (United States)

Schoefer, L; Braune, A; Blaut, M

2001-11-13

A novel fluorescence quenching test for the detection of flavonoid degradation by microorganisms was developed. The test is based on the ability of the flavonoids to quench the fluorescence of 1,6-diphenyl-1,3,5-hexatriene (DPH). Several members of the anthocyanidins, flavones, isoflavones, flavonols, flavanones, dihydroflavanones, chalcones, dihydrochalcones and catechins were tested with regard to their quenching properties. The anthocyanidins were the most potent quenchers of DPH fluorescence, while the flavanones, dihydroflavanones and dihydrochalcones, quenched the fluorescence only weakly. The catechins had no visible impact on DPH fluorescence. The developed test allows a quick and easy differentiation between flavonoid-degrading and flavonoid-non-degrading bacteria. The investigation of individual reactions of flavonoid transformation with the developed test system is also possible.

Continuous excitation chlorophyll fluorescence parameters: a review for practitioners.

Science.gov (United States)

Banks, Jonathan M

2017-08-01

This review introduces, defines and critically reviews a number of chlorophyll fluorescence parameters with specific reference to those derived from continuous excitation chlorophyll fluorescence. A number of common issues and criticisms are addressed. The parameters fluorescence origin (F0) and the performance indices (PI) are discussed as examples. This review attempts to unify definitions for the wide range of parameters available for measuring plant vitality, facilitating their calculation and use. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Photoprotection in the antenna complexes of photosystem II: role of individual xanthophylls in chlorophyll triplet quenching.

Science.gov (United States)

Mozzo, Milena; Dall'Osto, Luca; Hienerwadel, Rainer; Bassi, Roberto; Croce, Roberta

2008-03-07

In this work the photoprotective role of all xanthophylls in LHCII, Lhcb4, and Lhcb5 is investigated by laser-induced Triplet-minus-Singlet (TmS) spectroscopy. The comparison of native LHCII trimeric complexes with different carotenoid composition shows that the xanthophylls in sites V1 and N1 do not directly contribute to the chlorophyll triplet quenching. The largest part of the triplets is quenched by the lutein bound in site L1, which is located in close proximity to the chlorophylls responsible for the low energy state of the complex. The lutein in the L2 site is also active in triplet quenching, and it shows a longer triplet lifetime than the lutein in the L1 site. This lifetime difference depends on the occupancy of the N1 binding site, where neoxanthin acts as an oxygen barrier, limiting the access of O(2) to the inner domain of the Lhc complex, thereby strongly contributing to the photostability. The carotenoid triplet decay of monomeric Lhcb1, Lhcb4, and Lhcb5 is mono-exponential, with shorter lifetimes than observed for trimeric LHCII, suggesting that their inner domains are more accessible for O(2). As for trimeric LHCII, only the xanthophylls in sites L1 and L2 are active in triplet quenching. Although the chlorophyll to carotenoid triplet transfer is efficient (95%) in all complexes, it is not perfect, leaving 5% of the chlorophyll triplets unquenched. This effect appears to be intrinsically related to the molecular organization of the Lhcb proteins.

Fluorescence quenching of fluorescein by Merocyanine 540 in liposomes

International Nuclear Information System (INIS)

Toprak, Mahmut; Meryem Aydin, Burcu; Arik, Mustafa; Onganer, Yavuz

2011-01-01

The fluorescence quenching of fluorescein (FL) by merociyanine 540 (MC540) was examined in L-egg lecithin phosphatidycholine (PC) liposomes using spectroscopic methods. The type of quenching mechanism (dynamic or static) was evaluated using the Stern-Volmer plots. Findings were also supported by the temperature studies and florescence decay measurements. The Stern-Volmer equation was utilized to calculate bimolecular quenching constants (K q ). Furthermore, the bimolecular quenching constant of the quencher in the liposomes (K SV ), partition coefficient (K p ), binding constant (K), and corresponding thermodynamic parameters ΔH, ΔS, and ΔG were calculated. The quenching property was also used in determining quantitatively (K p ) the partition coefficient of Merociyanini 540 in PC liposome.The obtained data indicated that static quenching occurred in the system and the K SV values decreased with increasing lipid concentration. In addition, thermodynamic analysis suggested that van der Waals interactions and hydrogen bonding were the main acting forces between fluorescein and merociyanine 540 molecules in the medium. - Highlights: → Fluorescence quenching of FL by MC540 in liposome system was analyzed. → Fluorescence quenching mechanism of FL by MC540 was consistent with the static model. → Binding FL to MC540 was spontaneous and carried out by hydrogen bond and van der Waals forces.

Towards a merged satellite and in situ fluorescence ocean chlorophyll product

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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

A chlorophyll fluorescence-based method for the integrated characterization of the photophysiological response to light stress.

Science.gov (United States)

Serôdio, João; Schmidt, William; Frankenbach, Silja

2017-02-01

This work introduces a new experimental method for the comprehensive description of the physiological responses to light of photosynthetic organisms. It allows the integration in a single experiment of the main established manipulative chlorophyll fluorescence-based protocols. It enables the integrated characterization of the photophysiology of samples regarding photoacclimation state (generating non-sequential light-response curves of effective PSII quantum yield, electron transport rate or non-photochemical quenching), photoprotection capacity (running light stress-recovery experiments, quantifying non-photochemical quenching components) and the operation of photoinactivation and photorepair processes (measuring rate constants of photoinactivation and repair for different light levels and the relative quantum yield of photoinactivation). The new method is based on a previously introduced technique, combining the illumination of a set of replicated samples with spatially separated actinic light beams of different intensity, and the simultaneous measurement of the fluorescence emitted by all samples using an imaging fluorometer. The main novelty described here is the independent manipulation of light intensity and duration of exposure for each sample, and the control of the cumulative light dose applied. The results demonstrate the proof of concept for the method, by comparing the responses of cultures of Chlorella vulgaris acclimated to low and high light regimes, highlighting the mapping of light stress responses over a wide range of light intensity and exposure conditions, and the rapid generation of paired light-response curves of photoinactivation and repair rate constants. This approach represents a chlorophyll fluorescence 'protocol of everything', contributing towards the high throughput characterization of the photophysiology of photosynthetic organisms. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental

PsbS-specific zeaxanthin-independent changes in fluorescence emission spectrum as a signature of energy-dependent non-photochemical quenching in higher plants.

Science.gov (United States)

Zulfugarov, Ismayil S; Tovuu, Altanzaya; Dogsom, Bolormaa; Lee, Chung Yeol; Lee, Choon-Hwan

2010-05-01

The PsbS protein of photosystem II is necessary for the development of energy-dependent quenching of chlorophyll (Chl) fluorescence (qE), and PsbS-deficient Arabidopsis plant leaves failed to show qE-specific changes in the steady-state 77 K fluorescence emission spectra observed in wild-type leaves. The difference spectrum between the quenched and un-quenched states showed a negative peak at 682 nm. Although the level of qE development in the zeaxanthin-less npq1-2 mutant plants, which lacked violaxanthin de-epoxidase enzyme, was only half that of wild type, there were no noticeable changes in this qE-dependent difference spectrum. This zeaxanthin-independent DeltaF682 signal was not dependent on state transition, and the signal was not due to photobleaching of pigments either. These results suggest that DeltaF682 signal is formed due to PsbS-specific conformational changes in the quenching site of qE and is a new signature of qE generation in higher plants.

Water relation, leaf gas exchange and chlorophyll a fluorescence imaging of soybean leaves infected with Colletotrichum truncatum.

Science.gov (United States)

Dias, Carla Silva; Araujo, Leonardo; Alves Chaves, Joicy Aparecida; DaMatta, Fábio M; Rodrigues, Fabrício A

2018-06-01

Considering the potential of anthracnose to decrease soybean yield and the need to gain more information regarding its effect on soybean physiology, the present study performed an in-depth analysis of the photosynthetic performance of soybean leaflets challenged with Colletotrichum truncatum by combining chlorophyll a fluorescence images with gas-exchange measurements and photosynthetic pigment pools. There were no significant differences between non-inoculated and inoculated plants in leaf water potential, apparent hydraulic conductance, net CO 2 assimilation rate, stomatal conductance to water vapor and transpiration rate. For internal CO 2 concentration, significant difference between non-inoculated and inoculated plants occurred only at 36 h after inoculation. Reductions in the values of the chlorophyll a fluorescence parameters [initial fluorescence (F 0 ), maximal fluorescence (F m ), maximal photosystem II quantum yield (F v /F m ), quantum yield of regulated energy dissipation (Y(NPQ))] and increases in effective PS II quantum yield (Y(II)), quantum yield of non-regulated energy dissipation Y(NO) and photochemical quenching coefficient (q P ) were noticed on the necrotic vein tissue in contrast to the surrounding leaf tissue. It appears that the impact of the infection by C. truncatum on the photosynthetic performance of the leaflets was minimal considering the preference of the fungus to colonize the veins. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Impact of petrochemicals on the photosynthesis of Halophila ovalis using chlorophyll fluorescence

International Nuclear Information System (INIS)

Ralph, P.J.; Burchett, M.D.

1998-01-01

Laboratory-cultured Halophila ovalis showed tolerance to petrochemical exposure up to 1% (w/v) solution of Bass Strait crude oil, an oil dispersant (Corexit 9527) and a mixture of crude oil and dispersant. Quantum yield, as measured by chlorophyll fluorescence, was the most sensitive measure of the photosynthetic processes affected by petrochemical. The results indicated clearly that chlorophyll fluorescence was effective at monitoring the onset and development of stress and recovery of H. ovalis when exposed to crude oil, dispersant and a mixture of the two compounds. Photosynthetic pigment content generally confirmed the chlorophyll fluorescence response; however, several anomalies occurred. (author)

ZnSe quantum dots based fluorescence quenching method for determination of paeoniflorin

International Nuclear Information System (INIS)

Chen, Zhi; Chen, Jiayi; Liang, Qiaowen; Wu, Dudu; Zeng, Yuaner; Jiang, Bin

2014-01-01

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 −7 mol L −1 . Moreover, the quenching mechanism was discussed to be a static quenching procedure, which was proved by quenching rate constant K q (1.02×10 13 L mol −1 s −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

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.

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

International Nuclear Information System (INIS)

Makarska-Bialokoz, Magdalena; Borowski, Piotr

2015-01-01

The process of association between 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H 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 5 mol −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 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

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.

Quenching of liquid scintillator fluorescence by chloroalkanes and chloroalkenes

International Nuclear Information System (INIS)

Hariharan, Chithra; Mishra, A.K.

2000-01-01

The fluorescence quenching of 2,5-diphenyloxazole (PPO) by a series of chloroalkanes and chloroalkenes including carbon tetrachloride, chloroform, dichloroethane, tetrachloroethane, dichloroethylene, trichloroethylene and tetrachloroethylene was studied in toluene as solvent at room temperature. CCl 4 was found to be the most efficient quencher in the series. The quenching was found to be appreciable and a positive deviation from linearity was observed in the Stern-Volmer (SV) plots for all the quenchers in the concentration range studied. From the studies of effect of temperature, solvent viscosity and excitation wavelength dependence for the PPO-CCl 4 system, it was inferred that non-linearity is due to the presence of a minor static quenching component in an overall dynamic quenching. The static (K S ) and the dynamic (K D ) quenching constants were calculated from the modified SV equation using quadratic least square fits. Fluorescence quenching experiments with CCl 4 were done for four other scintillators (POPOP, α-NPO, BBO and PBBO). The mechanism of quenching was established to be via charge-transfer, with the direction of transfer being from the scintillators to the chloroalkanes and chloroalkenes

Movement influences carambola leaflet chlorophyll fluorescence and temperature under sunny conditions

International Nuclear Information System (INIS)

Marler, T.E.; Lawton, P.D.

1995-01-01

Leaflets of 'Arkin', 'B-10', 'Kary', and 'Sri Kembangan' carambola (Averrhoa carambola L.) trees were restrained in a horizontal position for 3.5 h during midday under full sun conditions to determine the influence of overriding natural leaflet movement on adaxial chlorophyll fluorescence and temperature. Induced chlorophyll fluorescence obtained after 30 minutes of dark adaptation following the period of full sun exposure was affected by leaflet movement. Restrained leaflets exhibited a variable fluorescence (Fv)/peak fluorescence (Fm) of 0.48, while that of unrestrained leaflets was 0.65. Adaxial leaflet temperature of restrained leaflets was 6C higher than that of leaflets that were allowed to move. The influence of leaflet movement on temperature or chlorophyll fluorescence was not different among the four cultivars. However, mean Fv/Fm of 'Kary' and 'Sri Kembangan' was lower than that of 'B-10'. Our results indicate that the ability of carambola to change leaflet angle leads to lower temperature and higher photochemical efficiency than occurs when leaflets are not allowed to move naturally (vertically orient) under full sun conditions

Mahalanobis distance screening of Arabidopsis mutants with chlorophyll fluorescence

Czech Academy of Sciences Publication Activity Database

Codrea, C. C.; Hakala-Yatkin, M.; Karlund-Marttila, A.; Nedbal, Ladislav; Aittokallio, T.; Nevalainen, O. S.; Tyystjärvi, E.

2010-01-01

Roč. 105, č. 3 (2010), s. 273-283 ISSN 0166-8595 Institutional research plan: CEZ:AV0Z60870520 Keywords : arabidopsis thaliana * chlorophyll fluorescence * fluorescence imaging * mutant detection * outlier detection Subject RIV: EH - Ecology, Behaviour Impact factor: 2.410, year: 2010 http://www.springerlink.com/content/x3586512462pn006/

Tryptophan and ATTO 590: mutual fluorescence quenching and exciplex formation.

Science.gov (United States)

Bhattacharjee, Ujjal; Beck, Christie; Winter, Arthur; Wells, Carson; Petrich, Jacob W

2014-07-24

Investigation of fluorescence quenching of probes, such as ATTO dyes, is becoming an increasingly important topic owing to the use of these dyes in super-resolution microscopies and in single-molecule studies. Photoinduced electron transfer is their most important nonradiative pathway. Because of the increasing frequency of the use of ATTO and related dyes to investigate biological systems, studies are presented for inter- and intramolecular quenching of ATTO 590 with tryptophan. In order to examine intramolecular quenching, an ATTO 590-tryptophan conjugate was synthesized. It was determined that tryptophan is efficiently quenching ATTO 590 fluorescence by excited-state charge transfer and two charge transfer complexes are forming. In addition, it was discovered that an exciplex (whose lifetime is 5.6 ns) can be formed between tryptophan and ATTO 590, and it is suggested that the possibility of such exciplex formation should be taken into account when protein fluorescence is monitored in a system tagged with ATTO dyes.

DAYTIME VARIATIONS OF CHLOROPHYLL A FLUORESCENCE IN PAU D'ALHO SEEDLINGS

OpenAIRE

Bacarin, Marcos Antonio; Martinazzo, Emanuela Garbin; Cassol, Daniela; Falqueto, Antelmo Ralph; Silva, Diolina Moura

2016-01-01

ABSTRACT Analysis of transient and modulated fluorescence of chlorophyll a were made at one-hour intervals during an eight-hour period starting at 07:30h aiming to study mechanisms of photoprotection against high radiation and temperature in Gallesia integrifolia plants. Seeds were germinated inside plastic pots containing soil as substrate. At 120 days after emergence, chlorophyll fluorescence measurements were performed using Handy-PEA and FMS2 fluorometers. During the course of a day, an i...

[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.

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.

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

International Nuclear Information System (INIS)

Zvezdanovic, Jelena; Cvetic, Tijana; Veljovic-Jovanovic, Sonja; Markovic, Dejan

2009-01-01

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

Relationship of intertidal surface sediment chlorophyll concentration to hyper-spectral reflectance and chlorophyll fluorescence

NARCIS (Netherlands)

Kromkamp, J.C.; Morris, E.P.; Forster, R.M.; Honeywill, C.; Hagerthey, S.; Paterson, D.M.

2006-01-01

Estimating biomass of microphytobenthos (MPB) on intertidal mud flats is extremely difficult due to their patchy occurrence, especially at the scale of an entire mud flat. We tested two optical approaches that can be applied in situ: spectral reflectance and chlorophyll fluorescence. These two

Drought is Coming: Monitoring Vegetation Response to Water Scarcity through Variable Chlorophyll a Fluorescence

Science.gov (United States)

Guadagno, C. R.; Beverly, D.; Pleban, J. R.; Speckman, H. N.; Ewers, B. E.; Weinig, C.

2017-12-01

Aridity is one of the most pronounced environmental limits to plant survival, and understanding how plants respond to drought and recovery is crucial for predicting impacts on managed and natural ecosystems. Changes in soil moisture conditions induce a suite of physiological responses from the cell to ecosystem scale, complicating the assessment of drought effects. Characterizing early indicators of water scarcity across species can inform biophysical models with improved understanding of plant hydraulics. While indexes exist for drought monitoring across scales, many are unable to identify imminent vegetative drought. We explore a method of early diagnosis using leaf-level and kinetic imaging measures of variable chlorophyll a fluorescence. This is a fast and reliable tool capturing leaf physiological changes in advance of changes in NDVI or passive solar induced fluorescence. Both image and leaf level Pulse Amplitude Method (PAM) measurements illustrate the utility of variable chlorophyll a fluorescence for monitoring vegetative drought. Variable fluorescence was monitored across populations of crops, desert shrubs, montane conifers and riparian deciduous trees under variable water regimes. We found a strong correlation (R = 0.85) between the maximum efficiency of photosystem II measured using variable fluorescence (Fv'Fm') and leaf level electrolyte leakage, a proximal cause of drought stress induced by cellular damage in leaves. This association was confirmed in two gymnosperm species (Picea engelmannii and Pinus contorta) and for diverse varieties of the crop species Brassica rapa. The use of chlorophyll a fluorescence per image also allowed for early detection of drought in aspen (Populus tremuloides). These results provide evidence that variable chlorophyll fluorescence decreases between 25% and 70% in mild and severely droughted twigs with respect to ones collected from trees in wet soil conditions. While current systems for monitoring variable fluorescence

Analysis of fluorescence quenching of pyronin B and pyronin Y by molecular oxygen in aqueous solution

Energy Technology Data Exchange (ETDEWEB)

Celebi, Neslihan [Faculty of Arts and Sciences, Department of Chemistry, Atatuerk University, 25240 Erzurum (Turkey); Arik, Mustafa [Faculty of Arts and Sciences, Department of Chemistry, Atatuerk University, 25240 Erzurum (Turkey); Onganer, Yavuz [Faculty of Arts and Sciences, Department of Chemistry, Atatuerk University, 25240 Erzurum (Turkey)]. E-mail: yonganer@atauni.edu.tr

2007-09-15

The fluorescence quenching of pyronin B and pyronin Y molecules by molecular oxygen in aqueous solution was studied by using steady-state and time-resolved fluorescence and UV-Vis absorption spectroscopy techniques. In order to understand the quenching mechanism, fluorescence decays, absorption and fluorescence spectra of the probes were recorded as a function of the oxygen concentration and temperature. The quenching was found to be appreciable and shows positive deviation in the Stern-Volmer representation obtained from the fluorescence intensity ratio. Fluorescence quenching constants (k {sub q}) were calculated from the {tau} {sub o}/{tau} vs. [Q] plots having linear correlation and compared with calculated diffusion-controlled rate constants (k {sub diff}) values. Experimental results were in good agreement with the simultaneous dynamic and static quenching model.

Analysis of fluorescence quenching of pyronin B and pyronin Y by molecular oxygen in aqueous solution

International Nuclear Information System (INIS)

Celebi, Neslihan; Arik, Mustafa; Onganer, Yavuz

2007-01-01

The fluorescence quenching of pyronin B and pyronin Y molecules by molecular oxygen in aqueous solution was studied by using steady-state and time-resolved fluorescence and UV-Vis absorption spectroscopy techniques. In order to understand the quenching mechanism, fluorescence decays, absorption and fluorescence spectra of the probes were recorded as a function of the oxygen concentration and temperature. The quenching was found to be appreciable and shows positive deviation in the Stern-Volmer representation obtained from the fluorescence intensity ratio. Fluorescence quenching constants (k q ) were calculated from the τ o /τ vs. [Q] plots having linear correlation and compared with calculated diffusion-controlled rate constants (k diff ) values. Experimental results were in good agreement with the simultaneous dynamic and static quenching model

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

Using chlorophyll fluorescence to determine stress in Eucalyptus ...

African Journals Online (AJOL)

Using chlorophyll fluorescence to determine stress in Eucalyptus grandis seedlings: scientific paper. ... Southern Forests: a Journal of Forest Science ... factors affect the functioning of the photosynthetic system, the status of the photosynthetic apparatus is a good indicator of the plant in terms of stress and stress adaptation.

Time-resolved laser fluorescence spectroscopy of organic ligands by europium: Fluorescence quenching and lifetime properties

Science.gov (United States)

Nouhi, A.; Hajjoul, H.; Redon, R.; Gagné, J. P.; Mounier, S.

2018-03-01

Time-resolved Laser Fluorescence Spectroscopy (TRLFS) has proved its usefulness in the fields of biophysics, life science and geochemistry to characterize the fluorescence probe molecule with its chemical environment. The purpose of this study is to demonstrate the applicability of this powerful technique combined with Steady-State (S-S) measurements. A multi-mode factor analysis, in particular CP/PARAFAC, was used to analyze the interaction between Europium (Eu) and Humic substances (HSs) extracted from Saint Lawrence Estuary in Canada. The Saint Lawrence system is a semi-enclosed water stream with connections to the Atlantic Ocean and is an excellent natural laboratory. CP/PARAFAC applied to fluorescence S-S data allows introspecting ligands-metal interactions and the one-site 1:1 modeling gives information about the stability constants. From the spectral signatures and decay lifetimes data given by TRLFS, one can deduce the fluorescence quenching which modifies the fluorescence and discuss its mechanisms. Results indicated a relatively strong binding ability between europium and humic substances samples (Log K value varies from 3.38 to 5.08 at pH 7.00). Using the Stern-Volmer plot, it has been concluded that static and dynamic quenching takes places in the case of salicylic acid and europium interaction while for HSs interaction only a static quenching is observed.

Estimation of photosynthesis in cyanobacteria by pulse-amplitude modulation chlorophyll fluorescence: problems and solutions.

Science.gov (United States)

Ogawa, Takako; Misumi, Masahiro; Sonoike, Kintake

2017-09-01

Cyanobacteria are photosynthetic prokaryotes and widely used for photosynthetic research as model organisms. Partly due to their prokaryotic nature, however, estimation of photosynthesis by chlorophyll fluorescence measurements is sometimes problematic in cyanobacteria. For example, plastoquinone pool is reduced in the dark-acclimated samples in many cyanobacterial species so that conventional protocol developed for land plants cannot be directly applied for cyanobacteria. Even for the estimation of the simplest chlorophyll fluorescence parameter, F v /F m , some additional protocol such as addition of DCMU or illumination of weak blue light is necessary. In this review, those problems in the measurements of chlorophyll fluorescence in cyanobacteria are introduced, and solutions to those problems are given.

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.

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)

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

1996-12-31

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)

Intrinsic Fluorescence of PAMAM Dendrimers—Quenching Studies

Directory of Open Access Journals (Sweden)

Malgorzata Konopka

2018-05-01

Full Text Available Intrinsic, non-traditional fluorescence of polyamidoamine (PAMAM dendrimers that do not possess classical fluorophores has been attracting considerable interest for the last decade. Many hypotheses regarding the source of the fluorescence have appeared, but some of them are still disputable. In order to shed new light on the nature of the phenomenon, we applied quenchers that are normally used to study intrinsic fluorescence of proteins (i.e., KI, CsCl, and acrylamide. KI and acrylamide efficiently quenched steady state fluorescence of PAMAM G2, PAMAM G3, and PAMAM G4 dendrimers. Stern-Volmer plots exhibited a downward curvature that has been elucidated by heterogenous emission. We assume that there are two distinct fluorescent moieties in the dendrimer structure that are characterized by different accessibility to the quenchers.

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)

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

Interactions of hemin with bovine serum albumin and human hemoglobin: A fluorescence quenching study

Science.gov (United States)

Makarska-Bialokoz, Magdalena

2018-03-01

The binding interactions between hemin (Hmi) and bovine serum albumin (BSA) or human hemoglobin (HHb), respectively, have been examined in aqueous solution at pH = 7.4, applying UV-vis absorption, as well as steady-state, synchronous and three-dimensional fluorescence spectra techniques. Representative results received for both BSA and HHb intrinsic fluorescence proceeding from the interactions with hemin suggest the formation of stacking non-covalent and non-fluorescent complexes in both the Hmi-BSA and Hmi-HHb systems, with highly possible concurrent formation of a coordinate bond between a group on the protein surface and the metal in Hmi molecule. All the values of calculated parameters, the binding, fluorescence quenching and bimolecular quenching rate constants point to the involvement of static quenching in both the systems studied. The blue shift in the synchronous fluorescence spectra imply the participation of both tryptophan and tyrosine residues in quenching of BSA and HHb intrinsic fluorescence. Depicted outcomes suggest that hemin is supposedly able to influence the physiological functions of BSA and HHb, the most important blood proteins, particularly in case of its overuse.

Chlorophyll fluorescence, photochemical reflective index and normalized difference vegetative index during plant senescence.

Science.gov (United States)

Cordon, Gabriela; Lagorio, M Gabriela; Paruelo, José M

2016-07-20

The relationship between the Photochemical Reflectance Index (PRI), Normalized Difference Vegetation Index (NDVI) and chlorophyll fluorescence along senescence was investigated in this work. Reflectance and radiance measurements were performed at canopy level in grass species presenting different photosynthetic metabolism: Avena sativa (C3) and Setaria italica (C4), at different stages of the natural senescence process. Sun induced-chlorophyll fluorescence at 760nm (SIF 760 ) and the apparent fluorescence yield (SIF 760 /a, with a=irradiance at time of measurement) were extracted from the radiance spectra of canopies using the Fraunhofer Line Discrimination-method. The photosynthetic parameters derived from Kautsky kinetics and pigment content were also calculated at leaf level. Whilst stand level NDVI patterns were related to changes in the structure of canopies and not in pigment content, stand level PRI patterns suggested changes both in terms of canopy and of pigment content in leaves. Both SIF 760 /a and Φ PSII decreased progressively along senescence in both species. A strong increment in NPQ was evident in A. sativa while in S. italica NPQ values were lower. Our most important finding was that two chlorophyll fluorescence signals, Φ PSII and SIF 760 /a, correlated with the canopy PRI values in the two grasses assessed, even when tissues at different ontogenic stages were present. Even though significant changes occurred in the Total Chlr/Car ratio along senescence in both studied species, significant correlations between PRI and chlorophyll fluorescence signals might indicate the usefulness of this reflectance index as a proxy of photosynthetic RUE, at least under the conditions of this study. The relationships between stand level PRI and the fluorescence estimators (Φ PSII and SIF 760 /a) were positive in both cases. Therefore, an increase in PRI values as in the fluorescence parameters would indicate higher RUE. Copyright © 2016 Elsevier GmbH. All

Fluorescence Quenching of Alpha-Fetoprotein by Gold Nanoparticles: Effect of Dielectric Shell on Non-Radiative Decay

Science.gov (United States)

Zhu, Jian; Li, Jian-Jun; Wang, A.-Qing; Chen, Yu; Zhao, Jun-Wu

2010-09-01

Fluorescence quenching spectrometry was applied to study the interactions between gold colloidal nanoparticles and alpha-fetoprotein (AFP). Experimental results show that the gold nanoparticles can quench the fluorescence emission of adsorbed AFP effectively. Furthermore, the intensity of fluorescence emission peak decreases monotonously with the increasing gold nanoparticles content. A mechanism based on surface plasmon resonance-induced non-radiative decay was investigated to illuminate the effect of a dielectric shell on the fluorescence quenching ability of gold nanoparticles. The calculation results show that the increasing dielectric shell thickness may improve the monochromaticity of fluorescence quenching. However, high energy transfer efficiency can be obtained within a wide wavelength band by coating a thinner dielectric shell.

Detection of vegetation LUE based on chlorophyll fluorescence separation algorithm from Fraunhofer line

Science.gov (United States)

Liu, Liangyun; Zhang, Bing

2009-09-01

Photosynthetic efficiency is very important, and not yet generally assessable by remote sensing. Much research has proved the possibility of the separation of solar-induced chlorophyll fluorescence (ChlF) from the reflected hyperspectral data. As the 'probe' of plant photosynthesis, it is possible to detect photosynthetic light use efficiency (LUE) by the separated solar-induced ChlF. A diurnal experiment was carried out on winter wheat on Apr. 18, 2008, and the canopy radiance spectra and leaf LUE data were measured synchronously. The solar-induced chlorophyll fluorescence signals at 760nm and 688nm were separated from the reflected radiance spectral based on Fraunhofer lines in two oxygen absorption bands. The result showed that LUE was negatively correlated to the separated chlorophyll signals. The statistical models for LUE based on the solar-induced chlorophyll fluorescence values at 688 nm and 760 nm bands had correlation coefficients (R2) of 0.64 and 0.78, respectively. In addition, photochemical reflectance index (PRI) was also linked to LUE, and a statistical model for LUE based on PRI has a correlation coefficient (R2) of 0.66. The presented method provides a novel solution for monitoring LUE from remote sensing data.

Fluorescence quenching of newly synthesized biologically active coumarin derivative by aniline in binary solvent mixtures

International Nuclear Information System (INIS)

Evale, Basavaraj G.; Hanagodimath, S.M.

2009-01-01

The fluorescence quenching of newly synthesized coumarin (chromen-2-one) derivative, 4-(5-methyl-3-furan-2-yl-benzofuran-2-yl)-7-methyl-chromen-2-one (MFBMC) by aniline in different solvent mixtures of benzene and acetonitrile was determined at room temperature (296 K) by steady-state fluorescence measurements. The quenching is found to be appreciable and positive deviation from linearity was observed in the Stern-Volmer (S-V) plots in all the solvent mixtures. This could be explained by static and dynamic quenching models. The positive deviation in the S-V plot is interpreted in terms of ground-state complex formation model and sphere of action static quenching model. Various rate parameters for the fluorescence quenching process have been determined by using the modified Stern-Volmer equation. The sphere of action static quenching model agrees very well with experimental results. The dependence of Stern-Volmer constant K SV , on dielectric constant ε of the solvent mixture suggests that the fluorescence quenching is diffusion-limited. Further with the use of finite sink approximation model, it is concluded that these bimolecular quenching reactions are diffusion-limited. Using lifetime (τ o ) data, the distance parameter R' and mutual diffusion coefficient D are estimated independently.

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).

Gas exchange and chlorophyll a fluorescence parameters of ornamental bromeliads

Directory of Open Access Journals (Sweden)

Karina Gonçalves da Silva

2017-10-01

Full Text Available Gas exchange and chlorophyll a fluorescence are widely used in physiological and ecological studies; however, few studies have used these techniques with ornamental plants. This study tested the potential contribution of gas exchange and chlorophyll a fluorescence to evaluate the water and nutrients uptake by the tank and root system of epiphyte bromeliad Guzmania lingulata. For this purpose, we conducted an experiment with different water regime and another with different concentrations of nitrogen. The experiments were: 1 - Watering: Control (application of water into Tank and Root, Tank (watering into Tank, Root (watering Root and Drought (water suspension during the 90 days of experimentation and 2 - Nitrogen: Plants fertilized with Hoagland and Arnon nutrient solution exclusively into Tank or Root with nitrogen concentrations of control and 2.62 or 5.34 mM N applied as urea. The Fv /Fm ratio allowed comparing the treatments between experiments, demonstrating that Root and Tank both have the capacity to maintain G. lingulata photosynthetic activity and growth, while Drought treatment (water suspension was the limiting factor for energy conversion efficiency of PSII. However, gas exchange was more permissive as a parameter for comparing treatments in the nitrogen experiment, providing important information about the general aspects of the photosynthetic process in the watering experiment. Both gas exchange and chlorophyll a fluorescence can support the evaluation of G. lingulata physiological status and can be useful tools in ornamental horticultural studies.

Fluorescence quenching of polycyclic aromatic hydrocarbons within deep eutectic solvents and their aqueous mixtures

Energy Technology Data Exchange (ETDEWEB)

Pandey, Ashish; Yadav, Anita; Bhawna; Pandey, Siddharth, E-mail: sipandey@chemistry.iitd.ac.in

2017-03-15

Two common and popular deep eutectic solvents (DESs) composed of the salt choline chloride and H-bond donors glycerol and urea in 1:2 mol ratio named glyceline and reline, respectively, are investigated for the analysis of polycyclic aromatic hydrocarbons (PAHs) using quenching of both steady-state and time-resolved fluorescence of ten different PAHs by nitromethane at 30 °C. Based on their quenching efficiencies, the PAHs are divided into two groups – group 1 is constituted of the five PAHs whose fluorescence are quenched less effectively by nitromethane whereas the other five exhibiting high quenching efficiency are associated to group 2. Quenching of steady-state fluorescence of group 1 PAHs by nitromethane, albeit not very significant, follow a simple Stern-Volmer behavior. The excited-state emission intensity decay of these PAHs, in both absence and presence of nitromethane, fit best to a single exponential model with small but monotonic decrease in lifetimes. The decrease in lifetime also follows Stern-Volmer behavior, however, the quenching constants (K{sub D}) are lower than those obtained from steady-state fluorescence (K{sub SV}). This is ascribed to the possible formation of charge-transfer complex between the PAH and the nitromethane. Steady-state fluorescence quenching of group 2 PAHs exhibit distinct upward curvature from linear Stern-Volmer behavior implying highly efficient quenching. The intensity decay fits best to a double exponential decay model with longer of the decay times following simple Stern-Volmer behavior. Formation of a complex or the presence of nitromethane within the quenching sphere of action of the PAH having short decay time is proposed. Quenching behavior was found to be similar irrespective of the identity of the DES. A representative group 2 PAH, pyrene, is employed to investigate diffusion dynamics within aqueous mixtures of the two DESs. The bimolecular quenching rate constant (k{sub q}) is found to increase linearly with

Poly(o-phenylenediamine) colloid-quenched fluorescent oligonucleotide as a probe for fluorescence-enhanced nucleic acid detection.

Science.gov (United States)

Tian, Jingqi; Li, Hailong; Luo, Yonglan; Wang, Lei; Zhang, Yingwei; Sun, Xuping

2011-02-01

In this Letter, we demonstrate that chemical oxidation polymerization of o-phenylenediamine (OPD) by potassium bichromate at room temperature results in the formation of submicrometer-scale poly(o-phenylenediamine) (POPD) colloids. Such colloids can absorb and quench dye-labeled single-stranded DNA (ssDNA) very effectively. In the presence of a target, a hybridization event occurs, which produces a double-stranded DNA (dsDNA) that detaches from the POPD surface, leading to recovery of dye fluorescence. With the use of an oligonucleotide (OND) sequence associated with human immunodeficiency virus (HIV) as a model system, we demonstrate the proof of concept that POPD colloid-quenched fluorescent OND can be used as a probe for fluorescence-enhanced nucleic acid detection with selectivity down to single-base mismatch.

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

International Nuclear Information System (INIS)

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

2014-01-01

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 N ), stomatal conductance (g s ), intercellular CO 2 (C i ) and chlorophyll fluorescence were measured. Ozone (O 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 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 3 . The maximum impairment in P N was recorded in the cultivar Victory (46%) in 2013 when the highest O 3 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 P N and C i , indicating the importance of non-stomatal limitations of photosynthesis, especially in the cultivar Victory. The P N vs. Ci curves were fitted to a non-rectangular hyperbolic model. The actual quantum yield (Φ 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 3 ) concentrations recorded were within the ranges of phytotoxicity. • O 3 has a clear influence on the physiological parameters. • O 3 decreased Photosynthetic rates, chlorophyll

Contribution of chlorophyll fluorescence to the apparent vegetation reflectance

International Nuclear Information System (INIS)

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

2008-01-01

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

Quenching of bacteriochlorophyll fluorescence in chlorosomes from Chloroflexus aurantiacus by exogenous quinones

DEFF Research Database (Denmark)

Tokita, S; Frigaard, N-U; Hirota, M

2000-01-01

The quenching of bacteriochlorophyll (BChl) c fluorescence in chlorosomes isolated from Chloroflexus aurantiacus was examined by the addition of various benzoquinones, naphthoquinones (NQ), and anthraquinones (AQ). Many quinones showed strong quenching in the micromolar or submicromolar range. Th...

Selective fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene by nucleotides.

Science.gov (United States)

Marquez, Cesar; Pischel, Uwe; Nau, Werner M

2003-10-16

[reaction: see text] The fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by nucleotides has been studied. The quenching mechanism was analyzed on the basis of deuterium isotope effects, tendencies for exciplex formation, and the quenching efficiency in the presence of a molecular container (cucurbit[7]uril). Exciplex-induced quenching appears to prevail for adenosine, cytidine, and uridine, while hydrogen abstraction becomes competitive for thymidine and guanosine. Compared to other fluorescent probes, DBO responds very selectively to the type of nucleotide.

On the origin of the slow M-T chlorophyll a fluorescence decline in cyanobacteria: interplay of short-term light-responses.

Science.gov (United States)

Bernát, Gábor; Steinbach, Gábor; Kaňa, Radek; Govindjee; Misra, Amarendra N; Prašil, Ondřej

2018-05-01

The slow kinetic phases of the chlorophyll a fluorescence transient (induction) are valuable tools in studying dynamic regulation of light harvesting, light energy distribution between photosystems, and heat dissipation in photosynthetic organisms. However, the origin of these phases are not yet fully understood. This is especially true in the case of prokaryotic oxygenic photoautotrophs, the cyanobacteria. To understand the origin of the slowest (tens of minutes) kinetic phase, the M-T fluorescence decline, in the context of light acclimation of these globally important microorganisms, we have compared spectrally resolved fluorescence induction data from the wild type Synechocystis sp. PCC 6803 cells, using orange (λ = 593 nm) actinic light, with those of mutants, ΔapcD and ΔOCP, that are unable to perform either state transition or fluorescence quenching by orange carotenoid protein (OCP), respectively. Our results suggest a multiple origin of the M-T decline and reveal a complex interplay of various known regulatory processes in maintaining the redox homeostasis of a cyanobacterial cell. In addition, they lead us to suggest that a new type of regulatory process, operating on the timescale of minutes to hours, is involved in dissipating excess light energy in cyanobacteria.

Investigation of common fluorophores for the detection of nitrated explosives by fluorescence quenching

International Nuclear Information System (INIS)

Meaney, Melissa S.; McGuffin, Victoria L.

2008-01-01

Previous studies have indicated that nitrated explosives may be detected by fluorescence quenching of pyrene and related compounds. The use of pyrene, however, invokes numerous health and waste disposal hazards. In the present study, ten safer fluorophores are identified for quenching detection of target nitrated compounds. Initially, Stern-Volmer constants are measured for each fluorophore with nitrobenzene and 4-nitrotoluene to determine the sensitivity of the quenching interaction. For quenching constants greater than 50 M -1 , sensitivity and selectivity are investigated further using an extended set of target quenchers. Nitromethane, nitrobenzene, 4-nitrotoluene, and 2,6-dinitrotoluene are chosen to represent nitrated explosives and their degradation products; aniline, benzoic acid, and phenol are chosen to represent potential interfering compounds. Among the fluorophores investigated, purpurin, malachite green, and phenol red demonstrate the greatest sensitivity and selectivity for nitrated compounds. Correlation of the quenching rate constants for these fluorophores to Rehm-Weller theory suggests an electron-transfer quenching mechanism. As a result of the large quenching constants, purpurin, malachite green, and phenol red are the most promising for future detection of nitrated explosives via fluorescence quenching

Responses of sun-induced chlorophyll fluorescence to biological and environmental variations measured with a versatile Fluorescence Auto-Measurement Equipment (FAME)

Science.gov (United States)

Gu, L.

2017-12-01

In this study, we examine responses of sun-induced chlorophyll fluorescence to biological and environmental variations measured with a versatile Fluorescence Auto-Measurement Equipment (FAME). FAME was developed to automatically and continuously measure chlorophyll fluorescence (F) of a leaf, plant or canopy in both laboratory and field environments, excited by either artificial light source or sunlight. FAME is controlled by a datalogger and allows simultaneous measurements of environmental variables complementary to the F signals. A built-in communication system allows FAME to be remotely monitored and data-downloaded. Radiance and irradiance calibrations can be done online. FAME has been applied in a variety of environments, allowing an investigation of biological and environmental controls on F emission.

Distinct roles of the photosystem II protein PsbS and zeaxanthin in the regulation of light harvesting in plants revealed by fluorescence lifetime snapshots.

Science.gov (United States)

Sylak-Glassman, Emily J; Malnoë, Alizée; De Re, Eleonora; Brooks, Matthew D; Fischer, Alexandra Lee; Niyogi, Krishna K; Fleming, Graham R

2014-12-09

The photosystem II (PSII) protein PsbS and the enzyme violaxanthin deepoxidase (VDE) are known to influence the dynamics of energy-dependent quenching (qE), the component of nonphotochemical quenching (NPQ) that allows plants to respond to fast fluctuations in light intensity. Although the absence of PsbS and VDE has been shown to change the amount of quenching, there have not been any measurements that can detect whether the presence of these proteins alters the type of quenching that occurs. The chlorophyll fluorescence lifetime probes the excited-state chlorophyll relaxation dynamics and can be used to determine the amount of quenching as well as whether two different genotypes with the same amount of NPQ have similar dynamics of excited-state chlorophyll relaxation. We measured the fluorescence lifetimes on whole leaves of Arabidopsis thaliana throughout the induction and relaxation of NPQ for wild type and the qE mutants, npq4, which lacks PsbS; npq1, which lacks VDE and cannot convert violaxanthin to zeaxanthin; and npq1 npq4, which lacks both VDE and PsbS. These measurements show that although PsbS changes the amount of quenching and the rate at which quenching turns on, it does not affect the relaxation dynamics of excited chlorophyll during quenching. In addition, the data suggest that PsbS responds not only to ΔpH but also to the Δψ across the thylakoid membrane. In contrast, the presence of VDE, which is necessary for the accumulation of zeaxanthin, affects the excited-state chlorophyll relaxation dynamics.

A transthylakoid proton gradient and inhibitors induce a non-photochemical fluorescence quenching in unicellular algae Nannochloropsis sp.

Science.gov (United States)

Cao, Shaona; Zhang, Xiaowen; Xu, Dong; Fan, Xiao; Mou, Shanli; Wang, Yitao; Ye, Naihao; Wang, Wenqi

2013-05-02

Non-photochemical quenching (NPQ) of chlorophyll fluorescence is thought to be an indicator of an essential regulation and photoprotection mechanism against high-light stress in photosynthetic organisms. In this report, special chemicals were used to perturb the kinetics of the ΔpH build-up and the xanthophyll cycle (XC) in Nannochloropsis sp. We found that NPQ was stimulated rapidly on exposure to high light and relaxed rapidly in darkness. The ΔpH could be obligatory for NPQ and ΔpH alone was not sufficient to induce NPQ. The XC, being strictly mediated by ΔpH, was also essential for NPQ. The results demonstrate that the mechanism of NPQ in Nannochloropsis sp. resembled that of diatoms. Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Fluctuation kinetics of fluorescence hopping quenching in the Nd3+:Y2O3 spherical nanoparticles

International Nuclear Information System (INIS)

Orlovskii, Yu.V.; Popov, A.V.; Platonov, V.V.; Fedorenko, S.G.; Sildos, I.; Osipov, V.V.

2013-01-01

We study the peculiarities of energy transfer kinetics from the 4 F 3/2 laser level in the Nd 3+ doped Y 2 O 3 spherical nanoparticles of monoclinic phase synthesized by laser ablation of solid targets with subsequent recondensation in flow of air at atmospheric pressure comparing to the similar bulk crystal. We show that the fluorescence quenching in the nanoparticles is determined by two processes depending on Nd 3+ concentration and the degree of dehydration. At concentrations less than 1% the fluorescence quenching is mainly determined by direct (static) quenching by vibrations of OH − molecular groups associated with oxygen vacancies. At concentrations greater than 1 at % quenching is due to energy migration over neodymium ions, followed by the Nd 3+ –OH − quenching. In the latter case, the first time in a solid-state impurity laser medium we observe non-stationary kinetics on the entire length of a time-dependent luminescence quenching, starting from static decay and ending with fluctuation kinetics of fluorescence hopping quenching. -- Highlights: ► We prepare monoclinic Nd 3+ :Y 2 O 3 spherical NPs of mean D=12 nm by laser ablation of solid targets. ► We detect the fluorescence quenching of Nd 3+ the 4 F 3/2 level by vibrations of OH – molecular groups. ► We find that at 0.1% of Nd 3+ the process of static quenching by vibrations of OH – dominates. ► We find that Nd 3+ –Nd 3+ energy migration accelerates the Nd 3+ –OH − quenching at 1% of Nd 3+ . ► We detect non-stationary quenching kinetics ending with fluctuation stage of hopping quenching

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.

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.

Probing Contaminant-Induced Alterations in Chlorophyll Fluorescence by AC-Dielectrophoresis-Based 2D-Algal Array

Directory of Open Access Journals (Sweden)

Coralie Siebman

2018-02-01

Full Text Available The investigation of contaminant impact on algae requires rapid and reliable cell collection and optical detection. The capability of alternative current (AC dielectrophoresis (DEP collection of whole cell arrays with combined fluorescence microscopy detection to follow the alterations of chlorophyll fluorescence during environmental contaminant exposure was explored. The application of an AC-field of 100 V cm−1, 100 Hz for 30 min to capture and immobilize the cells of green alga Chlamydomonas reinhardtii in two-dimensional (2D arrays does not induce changes in chlorophyll fluorescence. The results demonstrate that DEP-based 2D-arrays allow non-invasive detection of chlorophyll fluorescence change upon exposure to high concentrations of copper oxide nanoparticles and ionic copper. These results were in agreement with data obtained by flow cytometry used as a comparative method. The tool was also applied to follow the effect of a number of ubiquitous contaminants such as inorganic mercury, methylmercury, and diuron. However, a statistically significant short-term effect was observed only for mercury. Overall, DEP-based 2D-arrays of algal cells with fluorescence detection appear to be suitable for stain-free probing the effects on the photosynthetic microorganisms in highly polluted environment.

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.

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.

Quenching of acridine orange fluorescence by salts in aqueous solutions: Effects of aggregation and charge transfer

Energy Technology Data Exchange (ETDEWEB)

Amado, A.M. [Departamento de Física, FFCLRP, USP (Brazil); Ramos, A.P. [Departamento de Química, FFCLRP, USP (Brazil); Silva, E.R. [Departamento de Física, FFCLRP, USP (Brazil); Borissevitch, I.E., E-mail: iouribor@usp.br [Departamento de Física, FFCLRP, USP (Brazil)

2016-10-15

Acridine orange (AO) is widely applied in biology and medicine as a fluorescence probe, an intracellular pH indicator, and a photosensitizer in photodynamic therapy due to its adequate spectroscopic characteristics and high affinity to biological structures. Being introduced in an organism, AO is dispersed in blood plasma characterized by high ionic strength (ca. 0.36 M in humans). We have investigated the effect of ionic strength upon AO spectral characteristics and fluorescence quenching. The effect of pH on these characteristics was also tested. Salts quench AO fluorescence, the quenching constant (k{sub q}) increasing with the AO concentration. Salts stimulate AO aggregation, the process depending weakly on the salt origin. On the other hand, k{sub q} does depend on the salt anion origin, increasing as the anion oxidation potential decreases, and is virtually independent of the cation origin. This means that at least two different mechanisms of the AO fluorescence quenching by salts exist: fluorescence intensity decrease due to AO aggregation and quenching by partial electron transfer from salt anion to AO molecule in its singlet excited state (the exciplex formation).

Chlorophyll fluorescence, Orbital and Photosynthesis: practical activities integrating concepts of Chemistry, Physics and Biology

Directory of Open Access Journals (Sweden)

Elgion Lucio da Silva Loreto

2013-11-01

Full Text Available These laboratory activities explore the relationship between the reserve of energy that occur during photosynthesis and the chlorophyll fluorescence emission when in solution as opposed to absence of fluorescence when the chlorophyll are in intact chloroplasts. This proposal can be used as short demo or as  activities with longer duration, to show chlorophyll's properties associated with the photosynthesis. The materials proposed for the implementation of the activities are simple, and possible to building it by the students, enabling the development of various skills and experimental proposals. The protocols are based on observations and record key questions to continue the execution. During the activities, questions promotes pauses for moments of reflection and review of concepts. At the end are presented and discussed proposals for development of interdisciplinary projects.

Photosynthesis, chlorophyll fluorescence, light-harvesting system and photoinhibition resistance of a zeaxanthin-accumulating mutant of Arabidopsis thaliana.

Science.gov (United States)

Tardy, F; Havaux, M

1996-06-01

The abscisic-acid-deficient aba-1 mutant of Arabidopsis thaliana is unable to epoxidize zeaxanthin. As a consequence, it contains large amounts of this carotenoid and lacks epoxy-xanthophylls. HPLC analysis of pigment contents in leaves, isolated thylakoids and preparations of the major light-harvesting complex of photosystem II (PSII) (LHC-II) indicated that zeaxanthin replaced neoxanthin, violaxanthin and antheraxanthin in the light-harvesting system of PSII in aba-1. Non-denaturing electrophoretic fractionation of solubilized thylakoids showed that the xanthophyll imbalance in aba-1 was associated with a pronounced decrease in trimeric LHC-II in favour of monomeric complexes, with a substantial increase in free pigments (mainly zeaxanthin and chlorophyll b), suggesting a decreased stability of LHC-II. The reduced thermostability of PSII in aba-1 was also deduced from in vivo chlorophyll fluorescence measurements. Wild-type and aba-1 leaves could not be distinguished on the basis of their photosynthetic performance: no significant difference was observed between the two types of leaves for light-limited and light-saturated photosynthetic oxygen evolution, PSII photochemistry and PSII to PSI electron flow. When dark-adapted leaves (grown in white light of 80 mumol m-2s-1) were suddenly exposed to red light of 150 mumol m-2s-1, there was a strong nonphotochemical quenching of chlorophyll fluorescence, the amplitude of which was virtually identical (at steady state) in aba-1 and wild-type leaves, despite the fact that the xanthophyll cycle pigment pool was completely in the form of zeaxanthin in aba-1 and almost exclusively in the form of violaxanthin in the wild type. A high concentration of zeaxanthin in aba-1 thylakoids did not, in itself, provide any particular protection against the photoinhibition of PSII. Taken together, the presented results indicate the following: (1) zeaxanthin can replace epoxy-xanthophylls in LHC-II without significantly affecting the

Photochemical and photoelectrochemical quenching of chlorophyll fluorescence in photosystem II

NARCIS (Netherlands)

Vredenberg, W.J.; Durchan, M.; Prasil, O.

2009-01-01

This paper deals with kinetics and properties of variable fluorescence in leaves and thylakoids upon excitation with low intensity multi-turnover actinic light pulses corresponding with an excitation rate of about 10 Hz. These show a relatively small and amply documented rise in the sub-s time range

Quenching of chlorophyll a singlets and triplets by carotenoids in light-harvesting complex of photosystem II: comparison of aggregates with trimers

Science.gov (United States)

Naqvi, K. Razi; Melø, T. B.; Raju, B. Bangar; Jávorfi, Tamás; Simidjiev, Ilian; Garab, Gyözö

1997-12-01

Laser-induced changes in the absorption spectra of isolated light-harvesting chlorophyll a/ b complex (LHC II) associated with photosystem II of higher plants have been recorded under anaerobic conditions and at ambient temperature by using multichannel detection with sub-microsecond time resolution. Difference spectra (Δ A) of LHC II aggregates have been found to differ from the corresponding spectra of trimers on two counts: (i) in the aggregates, the carotenoid (Car) triplet-triplet absorption band (Δ A>0) is red-shifted and broader; and (ii) the features attributable to the perturbation of the Qy band of a chlorophyll a (Chl a) by a nearby Car triplet are more pronounced, than in trimers. Aggregation, which is known to be accompanied by a reduction in the fluorescence yield of Chl a, is shown to cause a parallel decline in the triplet formation yield of Chl a; on the other hand, the efficiency (100%) of Chl a-to-Car transfer of triplet energy and the lifetime (9.3 μs) of Car triplets are not affected by aggregation. These findings are rationalized by postulating that the antenna Cars transact, besides light-harvesting and photoprotection, a third process: energy dissipation within the antenna. The suggestion is advanced that luteins, which are buried inside the LHC II monomers, as well as the other, peripheral, xanthophylls (neoxanthin and violaxanthin) quench the excited singlet state of Chl a by catalyzing internal conversion, a decay channel that competes with fluorescence and intersystem crossing; support for this explanation is presented by recalling reports of similar behaviour in bichromophoric model compounds in which one moiety is a Car and the other a porphyrin or a pyropheophorbide.

Fluorescence ELISA for sensitive detection of ochratoxin A based on glucose oxidase-mediated fluorescence quenching of CdTe QDs

International Nuclear Information System (INIS)

Liang, Yi; Huang, Xiaolin; Yu, Ruijin; Zhou, Yaofeng; Xiong, Yonghua

2016-01-01

The present study described a novel fluorescence enzyme-linked immunosorbent assay (ELISA) used to detect ochratoxin A (OTA) by using the glucose oxidase (GOx)-mediated fluorescence quenching of mercaptopropionic acid-capped CdTe quantum dots (MPA-QDs), in which GOx was used as an alternative to horseradish peroxidase (HRP) for the oxidization of glucose into hydrogen peroxide (H_2O_2) and gluconic acid. The MPA-QDs were used as a fluorescent signal output, whose fluorescence variation was extremely sensitive to the presence of H_2O_2 or hydrogen ions in the solution. Under the optimized conditions, the proposed fluorescence ELISA demonstrated a good linear detection of OTA in corn extract from 2.4 pg mL"−"1 to 625 pg mL"−"1 with a limit of detection of 2.2 pg mL"−"1, which was approximately 15-fold lower than that of conventional HRP-based ELISA. Our developed fluorescence immunoassay was also similar to HRP-based ELISA in terms of selectivity, accuracy, and reproducibility. In summary, this study was the first to use the GOx-mediated fluorescence quenching of QDs in immunoassay to detect OTA, offering a new possibility for the analysis of other mycotoxins and biomolecules. - Highlights: • A novel fluorescence ELISA was first developed for the detection of OTA by using GOx-mediated fluorescence quenching of QDs. • The pH- and H_2O_2-sensitive MPA-capped CdTe QDs were used as a fluorescent signal output to improve the detection sensitivity. • This novel method open up a different vision to detect other mycotoxins and biomolecules.

DNA-length-dependent quenching of fluorescently labeled iron oxide nanoparticles with gold, graphene oxide and MoS2 nanostructures.

Science.gov (United States)

Balcioglu, Mustafa; Rana, Muhit; Robertson, Neil; Yigit, Mehmet V

2014-08-13

We controlled the fluorescence emission of a fluorescently labeled iron oxide nanoparticle using three different nanomaterials with ultraefficient quenching capabilities. The control over the fluorescence emission was investigated via spacing introduced by the surface-functionalized single-stranded DNA molecules. DNA molecules were conjugated on different templates, either on the surface of the fluorescently labeled iron oxide nanoparticles or gold and nanographene oxide. The efficiency of the quenching was determined and compared with various fluorescently labeled iron oxide nanoparticle and nanoquencher combinations using DNA molecules with three different lengths. We have found that the template for DNA conjugation plays significant role on quenching the fluorescence emission of the fluorescently labeled iron oxide nanoparticles. We have observed that the size of the DNA controls the quenching efficiency when conjugated only on the fluorescently labeled iron oxide nanoparticles by setting a spacer between the surfaces and resulting change in the hydrodynamic size. The quenching efficiency with 12mer, 23mer and 36mer oligonucleotides decreased to 56%, 54% and 53% with gold nanoparticles, 58%, 38% and 32% with nanographene oxide, 46%, 38% and 35% with MoS2, respectively. On the other hand, the presence, not the size, of the DNA molecules on the other surfaces quenched the fluorescence significantly with different degrees. To understand the effect of the mobility of the DNA molecules on the nanoparticle surface, DNA molecules were attached to the surface with two different approaches. Covalently immobilized oligonucleotides decreased the quenching efficiency of nanographene oxide and gold nanoparticles to ∼22% and ∼21%, respectively, whereas noncovalently adsorbed oligonucleotides decreased it to ∼25% and ∼55%, respectively. As a result, we have found that each nanoquencher has a powerful quenching capability against a fluorescent nanoparticle, which can be

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.

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

A method for the rapid generation of nonsequential light-response curves of chlorophyll fluorescence.

Science.gov (United States)

Serôdio, João; Ezequiel, João; Frommlet, Jörg; Laviale, Martin; Lavaud, Johann

2013-11-01

Light-response curves (LCs) of chlorophyll fluorescence are widely used in plant physiology. Most commonly, LCs are generated sequentially, exposing the same sample to a sequence of distinct actinic light intensities. These measurements are not independent, as the response to each new light level is affected by the light exposure history experienced during previous steps of the LC, an issue particularly relevant in the case of the popular rapid light curves. In this work, we demonstrate the proof of concept of a new method for the rapid generation of LCs from nonsequential, temporally independent fluorescence measurements. The method is based on the combined use of sample illumination with digitally controlled, spatially separated beams of actinic light and a fluorescence imaging system. It allows the generation of a whole LC, including a large number of actinic light steps and adequate replication, within the time required for a single measurement (and therefore named "single-pulse light curve"). This method is illustrated for the generation of LCs of photosystem II quantum yield, relative electron transport rate, and nonphotochemical quenching on intact plant leaves exhibiting distinct light responses. This approach makes it also possible to easily characterize the integrated dynamic light response of a sample by combining the measurement of LCs (actinic light intensity is varied while measuring time is fixed) with induction/relaxation kinetics (actinic light intensity is fixed and the response is followed over time), describing both how the response to light varies with time and how the response kinetics varies with light intensity.

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

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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.

Fluorescence quenching of dye molecules near gold nanoparticles: radiative and nonradiative effects

NARCIS (Netherlands)

Dulkeith, E.; Morteani, A.C.; Niedereichholz, T.; Klar, T.A.; Feldman, J.; Levi, S.; van Veggel, F.C.J.M.; Reinhoudt, David; Möller, M.; Gittins, D.I.

2002-01-01

The radiative and nonradiative decay rates of lissamine dye molecules, chemically attached to differently sized gold nanoparticles, are investigated by means of time-resolved fluorescence experiments. A pronounced fluorescence quenching is observed already for the smallest nanoparticles of 1  nm

Investigation on Fluorescence Quenching Mechanism of Perylene Diimide Dyes by Graphene Oxide

Directory of Open Access Journals (Sweden)

Yuzhen Zhao

2016-11-01

Full Text Available Perylene diimide derivatives were used as probes to investigate the effect of the molecular structures on the fluorescence quenching mechanism in a perylene diimide/graphene oxide system. The electrons transferred from the excited state of dyes to the conductive band of graphene oxide with different concentrations were determined by fluorescence spectra. The results indicated that the quenching efficiency of perylene diimides by graphene oxide was not only dependent on the difference between the lowest unoccupied molecular orbital level of dyes and the conduction band of the graphene oxide, but also mainly on the difference in the molecular structures.

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.

Detection of Sn(II) ions via quenching of the fluorescence of carbon nanodots

International Nuclear Information System (INIS)

Mohd Yazid, S.N.A.; Chin, S.F.; Pang, S.C.; Ng, S.M.

2013-01-01

We report that fluorescent carbon nanodots (C-dots) can act as an optical probe for quantifying Sn(II) ions in aqueous solution. C-dots are synthesized by carbonization and surface oxidation of preformed sago starch nanoparticles. Their fluorescence is significantly quenched by Sn(II) ions, and the effect can be used to determine Sn(II) ions. The highest fluorescence intensity is obtained at a concentration of 1.75 mM of C-dots in aqueous solution. The probe is highly selective and hardly interfered by other ions. The quenching mechanism appears to be predominantly of the static (rather than dynamic) type. Under optimum conditions, there is a linear relationship between fluorescence intensity and Sn(II) ions concentration up to 4 mM, and with a detection limit of 0.36 μM. (author)

Fluorescence ELISA for sensitive detection of ochratoxin A based on glucose oxidase-mediated fluorescence quenching of CdTe QDs

Energy Technology Data Exchange (ETDEWEB)

Liang, Yi [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, 330047 (China); Jiangxi-OAI Joint Research Institute, Nanchang University, Nanchang 330047 (China); Huang, Xiaolin [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, 330047 (China); Yu, Ruijin [College of Science, Northwest A& F University, Yangling, Shaanxi 712100 (China); Zhou, Yaofeng [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, 330047 (China); Xiong, Yonghua, E-mail: yhxiongchen@163.com [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, 330047 (China); Jiangxi-OAI Joint Research Institute, Nanchang University, Nanchang 330047 (China)

2016-09-14

The present study described a novel fluorescence enzyme-linked immunosorbent assay (ELISA) used to detect ochratoxin A (OTA) by using the glucose oxidase (GOx)-mediated fluorescence quenching of mercaptopropionic acid-capped CdTe quantum dots (MPA-QDs), in which GOx was used as an alternative to horseradish peroxidase (HRP) for the oxidization of glucose into hydrogen peroxide (H{sub 2}O{sub 2}) and gluconic acid. The MPA-QDs were used as a fluorescent signal output, whose fluorescence variation was extremely sensitive to the presence of H{sub 2}O{sub 2} or hydrogen ions in the solution. Under the optimized conditions, the proposed fluorescence ELISA demonstrated a good linear detection of OTA in corn extract from 2.4 pg mL{sup −1} to 625 pg mL{sup −1} with a limit of detection of 2.2 pg mL{sup −1}, which was approximately 15-fold lower than that of conventional HRP-based ELISA. Our developed fluorescence immunoassay was also similar to HRP-based ELISA in terms of selectivity, accuracy, and reproducibility. In summary, this study was the first to use the GOx-mediated fluorescence quenching of QDs in immunoassay to detect OTA, offering a new possibility for the analysis of other mycotoxins and biomolecules. - Highlights: • A novel fluorescence ELISA was first developed for the detection of OTA by using GOx-mediated fluorescence quenching of QDs. • The pH- and H{sub 2}O{sub 2}-sensitive MPA-capped CdTe QDs were used as a fluorescent signal output to improve the detection sensitivity. • This novel method open up a different vision to detect other mycotoxins and biomolecules.

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

A two-component nonphotochemical fluorescence quenching in eustigmatophyte algae

Czech Academy of Sciences Publication Activity Database

Bína, David; Bouda, Karel; Litvín, Radek

2017-01-01

Roč. 131, č. 1 (2017), s. 65-77 ISSN 0166-8595 R&D Projects: GA ČR(CZ) GP14-01377P Institutional support: RVO:60077344 Keywords : Nonphotochemical quenching * Xanthophyll cycle * Chl a fluorescence Subject RIV: BO - Biophysics OBOR OECD: Biophysics Impact factor: 3.864, year: 2016

Qtl mapping of wheat doubled haploids for chlorophyll content and chlorophyll fluorescence kinetics under drought stress imposed at anthesis stage

International Nuclear Information System (INIS)

Ilyas, M.; Ilyas, N.; Arshad, M.; Kazi, A.G.

2014-01-01

Drought stress is one of the major environmental constraints to crop plants including wheat worldwide. Synthetic hexaploid can act as a vehicle for improving crop tolerance against biotic and abiotic stresses. Doubled haploid population consisting of one hundred and forty individuals derived from cross of Opata and SH223 was used in the present study to identify genomic regions associated with various quantitative attributes of physiological nature. Doubled haploid mapping population was phenotyped for chlorophyll content and chlorophyll fluorescence kinetics under control and drought stress imposed at anthesis stage. Genotyping of population was accomplished by utilizing two hundred and sixty one polymorphic Gaterslaben wheat microsatellites and Beltsville agriculture research center simple sequence repeats. Linkage map of doubled haploid population comprising of 19 linkage groups and covering map length of two thousands six hundred and twenty six (2626) cM was constructed using map maker software. Major and minor QTLs associated with quantitative traits were identified using QGene software. Major QTL for chlorophyll content (QTc.wwc-1B-S11) of doubled haploid mapping population under anthesis drought stress was mapped on chromosome 1B and explained 10.09 percent of phenotypic variation at LOD score of 5.5. Seven major and minor QTLs for PCFK of doubled haploids were identified on chromosome 1B, 7A and 7D under control and drought stress at anthesis stage. The identified QTLs are of prime importance for high resolution mapping in synthetic hexaploid wheat. Genomic synteny of doubled haploids was observed with rice chromosome 2, 4, 7 and maize chromosome 7 owing to occurrence of orthologous QTLs for chlorophyll content and chlorophyll fluorescence respectively. (author)

Determination of Cerium (IV) Using Rhodamine 6G Fluorescence Quenching

Science.gov (United States)

Zhao, Zh.; Sheng, L.; Su, B.; Tao, C.; Jing, W.

2017-11-01

The interaction between rhodamine 6G (Rh6G) and cerium sulfate was studied by the fluorescence quenching method. In a sulfuric acid medium, the interaction of Ce(IV) with Rh6G results in Rh6G fluorescence quenching. The maximum excitation wavelength (λex) and the maximum emission wavelength (λem) are 530 nm and 555 nm, respectively. A good linearity between the relative fl uorescence intensity (ΔF) and Ce(IV) was observed in the range 0.12-1.08 μg/mL. The detection limit was 1.4 × 10-3 μg/mL. The optimum reaction conditions, influencing factors, and effect of coexisting substances were investigated in the experiment. We found that the concentration of Rh6G was 3.2 × 10-6 mol/L, and the fl uorescence intensity was maximum.

Vertical distribution of chlorophyll a concentration and phytoplankton community composition from in situ fluorescence profiles: a first database for the global ocean

Science.gov (United States)

Sauzède, R.; Lavigne, H.; Claustre, H.; Uitz, J.; Schmechtig, C.; D'Ortenzio, F.; Guinet, C.; Pesant, S.

2015-10-01

In vivo chlorophyll a fluorescence is a proxy of chlorophyll a concentration, and is one of the most frequently measured biogeochemical properties in the ocean. Thousands of profiles are available from historical databases and the integration of fluorescence sensors to autonomous platforms has led to a significant increase of chlorophyll fluorescence profile acquisition. To our knowledge, this important source of environmental data has not yet been included in global analyses. A total of 268 127 chlorophyll fluorescence profiles from several databases as well as published and unpublished individual sources were compiled. Following a robust quality control procedure detailed in the present paper, about 49 000 chlorophyll fluorescence profiles were converted into phytoplankton biomass (i.e., chlorophyll a concentration) and size-based community composition (i.e., microphytoplankton, nanophytoplankton and picophytoplankton), using a method specifically developed to harmonize fluorescence profiles from diverse sources. The data span over 5 decades from 1958 to 2015, including observations from all major oceanic basins and all seasons, and depths ranging from the surface to a median maximum sampling depth of around 700 m. Global maps of chlorophyll a concentration and phytoplankton community composition are presented here for the first time. Monthly climatologies were computed for three of Longhurst's ecological provinces in order to exemplify the potential use of the data product. Original data sets (raw fluorescence profiles) as well as calibrated profiles of phytoplankton biomass and community composition are available on open access at PANGAEA, Data Publisher for Earth and Environmental Science. Raw fluorescence profiles: http://doi.pangaea.de/10.1594/PANGAEA.844212 and Phytoplankton biomass and community composition: http://doi.pangaea.de/10.1594/PANGAEA.844485

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

Science.gov (United States)

Li, Fengmei; Wei, Yaoguang; Chen, Yingyi; Li, Daoliang; Zhang, Xu

2015-12-09

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.

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.

Satellite-detected fluorescence reveals global physiology of ocean phytoplankton

Directory of Open Access Journals (Sweden)

M. J. Behrenfeld

2009-05-01

Full Text Available Phytoplankton photosynthesis links global ocean biology and climate-driven fluctuations in the physical environment. These interactions are largely expressed through changes in phytoplankton physiology, but physiological status has proven extremely challenging to characterize globally. Phytoplankton fluorescence does provide a rich source of physiological information long exploited in laboratory and field studies, and is now observed from space. Here we evaluate the physiological underpinnings of global variations in satellite-based phytoplankton chlorophyll fluorescence. The three dominant factors influencing fluorescence distributions are chlorophyll concentration, pigment packaging effects on light absorption, and light-dependent energy-quenching processes. After accounting for these three factors, resultant global distributions of quenching-corrected fluorescence quantum yields reveal a striking consistency with anticipated patterns of iron availability. High fluorescence quantum yields are typically found in low iron waters, while low quantum yields dominate regions where other environmental factors are most limiting to phytoplankton growth. Specific properties of photosynthetic membranes are discussed that provide a mechanistic view linking iron stress to satellite-detected fluorescence. Our results present satellite-based fluorescence as a valuable tool for evaluating nutrient stress predictions in ocean ecosystem models and give the first synoptic observational evidence that iron plays an important role in seasonal phytoplankton dynamics of the Indian Ocean. Satellite fluorescence may also provide a path for monitoring climate-phytoplankton physiology interactions and improving descriptions of phytoplankton light use efficiencies in ocean productivity models.

Metal-atom fluorescence from the quenching of metastable rare gases by metal carbonyls

International Nuclear Information System (INIS)

Hollingsworth, W.E.

1982-11-01

A flowing afterglow apparatus was used to study the metal fluorescence resulting from the quenching of metastable rare-gas states by metal carbonyls. The data from the quenching or argon, neon, and helium by iron and nickel carbonyl agreed well with a restricted degree of freedom model indicating a concerted bond-breaking dissociation

Using a Specific RNA-Protein Interaction To Quench the Fluorescent RNA Spinach.

Science.gov (United States)

Roszyk, Laura; Kollenda, Sebastian; Hennig, Sven

2017-12-15

RNAs are involved in interaction networks with other biomolecules and are crucial for proper cell function. Yet their biochemical analysis remains challenging. For Förster Resonance Energy Transfer (FRET), a common tool to study such interaction networks, two interacting molecules have to be fluorescently labeled. "Spinach" is a genetically encodable RNA aptamer that starts to fluoresce upon binding of an organic molecule. Therefore, it is a biological fluorophore tag for RNAs. However, spinach has never been used in a FRET assembly before. Here, we describe how spinach is quenched when close to acceptors. We used RNA-DNA hybridization to bring quenchers or red organic dyes in close proximity to spinach. Furthermore, we investigate RNA-protein interactions quantitatively on the example of Pseudomonas aeruginosa phage coat protein 7 (PP7) and its interacting pp7-RNA. We utilize spinach quenching as a fully genetically encodable system even under lysate conditions. Therefore, this work represents a direct method to analyze RNA-protein interactions by quenching the spinach aptamer.

Fluorescence quenching of N,N-bis(2,5-di-tert-butylphenyl)-3,4:9,10-perylenebis(dicarboximide) (DBPI) by silver nanoparticles

Energy Technology Data Exchange (ETDEWEB)

El-Daly, Samy A., E-mail: samyeldaly@yahoo.com [Chemistry Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah 21589 (Saudi Arabia); Chemistry Department, Faculty of Science, Tanta University, Tanta 2173 (Egypt); Rahman, Mohammed M. [Chemistry Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah 21589 (Saudi Arabia); Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, PO Box 80203, Jeddah 21589 (Saudi Arabia); Alamry, Kahlid A. [Chemistry Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah 21589 (Saudi Arabia); Asiri, Abdullah M. [Chemistry Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah 21589 (Saudi Arabia); Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, PO Box 80203, Jeddah 21589 (Saudi Arabia)

2014-04-15

The interaction of a perylene derivative namely N,N-bis(2,5-di-tert-butylphenyl)-3,4:9,10-perylenebis(dicarboximide) (DBPI) with colloidal silver nanoparticles (AgNPs) was studied in ethanol and ethylene glycol using steady state fluorescence quenching measurements. The Stern–Volmer quenching rate constant (K{sub sv}) was calculated as 4.03×10{sup 9} and 29.14×10{sup 9} M{sup −1} in ethanol and ethylene glycol, respectively. From fluorescence quenching data, static quenching and energy transfer play a major role in the fluorescence quenching of DBPI by AgNPs. The apparent association constant (k{sub app}) was calculated as 1.26×10{sup 8} M{sup −1} in EtOH and 1.83×10{sup 9} M{sup −1} in ethylene glycol. Due to potential AgNPs interaction with DBPI, the average AgNPs size is increased slightly from ∼37.1 nm (As-prepared) to 48.9 nm. -- Highlights: • Fluorescence quenching of photostable DBPI by AgNPs. • Static quenching mechanism of interaction between DBPI and AgNPs. • Enhancement of fluorescence quenching of DBPI in ethylene glycol.

Fluorescence quenching and photocatalytic degradation of textile dyeing waste water by silver nanoparticles

Science.gov (United States)

Kavitha, S. R.; Umadevi, M.; Janani, S. R.; Balakrishnan, T.; Ramanibai, R.

2014-06-01

Silver nanoparticles (Ag NPs) of different sizes have been prepared by chemical reduction method and characterized using UV-vis spectroscopy and transmission electron microscopy (HRTEM). Fluorescence spectral analysis showed that the quenching of fluorescence of textile dyeing waste water (TDW) has been found to decrease with decrease in the size of the Ag NPs. Experimental results show that the silver nanoparticles can quench the fluorescence emission of adsorbed TDW effectively. The fluorescence interaction between Ag NPs (acceptor) and TDW (donor) confirms the Förster Resonance Energy Transfer (FRET) mechanism. Long range dipole-dipole interaction between the excited donor and ground state acceptor molecules is the dominant mechanism responsible for the energy transfer. Furthermore, photocatalytic degradation of TDW was measured spectrophotometrically by using silver as nanocatalyst under UV light illumination. The kinetic study revealed that synthesized Ag NPs was found to be effective in degrading TDW.

Novel Spectrofluorimetric Method for the Determination of Perindopril Erbumine Based on Fluorescence Quenching of Rhodamine B.

Science.gov (United States)

Fael, Hanan; Sakur, Amir Al-Haj

2015-11-01

A novel, simple and specific spectrofluorimetric method was developed and validated for the determination of perindopril erbumine (PDE). The method is based on the fluorescence quenching of Rhodamine B upon adding perindopril erbumine. The quenched fluorescence was monitored at 578 nm after excitation at 500 nm. The optimization of the reaction conditions such as the solvent, reagent concentration, and reaction time were investigated. Under the optimum conditions, the fluorescence quenching was linear over a concentration range of 1.0-6.0 μg/mL. The proposed method was fully validated and successfully applied to the analysis of perindopril erbumine in pure form and tablets. Statistical comparison of the results obtained by the developed and reference methods revealed no significant differences between the methods compared in terms of accuracy and precision. The method was shown to be highly specific in the presence of indapamide, a diuretic that is commonly combined with perindopril erbumine. The mechanism of rhodamine B quenching was also discussed.

The effect of UV-B and UV-C radiation on Hibiscus leaves determined by ultraweak luminescence and fluorescence induction [chlorophyll fluorescence induction, ultraweak luminescence

International Nuclear Information System (INIS)

Panagopoulos, I.; Bornman, J.F.; Björn, L.O.

1989-01-01

The effects of UV-C (254 nm) and UV-B (280-320 nm) on chlorophyll fluorescence induction and ultraweak luminescence (UL) in detached leaves of Hibiscus rosa-sinensis L. were investigated. UL from leaves exposed to UV-B and UV-C radiation reached a maximum 72 h after irradiation. In both cases most of the light was of a wavelength over 600 nm. An increase in the percentage of long wavelength light with time was detected. UV radiation increased peroxidase activity, which also reached a maximum 72 h after irradiation. UV-B and UV-C both reduced variable chlorophyll fluorescence. No effect on the amount of chlorophyll or UV screening pigments was observed with the short-term irradiation used in this investigation. (author)

Measuring of the Chlorophyll a Fluorescence in Calcium Alginate-Encapsulated Algae

Directory of Open Access Journals (Sweden)

Ibeth Paola Delgadillo Rodríguez

2017-05-01

Full Text Available Immobilization of algae has many applications, such as water bioremediation and production of metabolites. One of the variables that can be determined in the immobilized algae is chlorophyll a fluorescence, because this parameter is related to the physiological response of these organisms. Therefore, the objective of this study was to explore a method for measuring the chlorophyll a fluorescence in calcium alginate-encapsulated algae. To do this, two species of microalgae (Scenedesmus ovalternus LAUN 001 and Parachlorella kessleri LAUN 002 were grown in monocultures in both free culture conditions (10 mL of algae preparation in 250 mL of Basal Bold Medium and encapsulated (250 spheres in 250 mL of Basal Bold Medium. Different measurement protocols of chlorophyll a fluorescence of photosystem II (PSII were performed by varying a the preadaptation time to darkness (10, 15 and 30 min, b the light intensity of the non-modulated fluorometer (between 1000 and 3500 μmoles m-2s-1, and c the time of exposure to actinic light (1, 2 and 5 s. The optimal conditions for the measurement of the maximum quantum yield of PSII (Fv/Fm in encapsulated algae were established as follow: a 30 min of preadaptation time; b 3000 μmoles m-2s-1 of the fluorometer light intensity; and c 1 to 2 s of exposure to actinic light. The following values in the photochemical activity of algae in non-stressful conditions were found: 0.760 – 0.764 for S. ovalternus, and 0.732 – 0.748 for P. kessleri. This methodology allows to observe some changes in the photochemical activity related with variations in the factors under which are the immobilized algae.

Error in interpreting field chlorophyll fluorescence measurements: heat gain from solar radiation

International Nuclear Information System (INIS)

Marler, T.E.; Lawton, P.D.

1994-01-01

Temperature and chlorophyll fluorescence characteristics were determined on leaves of various horticultural species following a dark adaptation period where dark adaptation cuvettes were shielded from or exposed to solar radiation. In one study, temperature of Swietenia mahagoni (L.) Jacq. leaflets within cuvettes increased from approximately 36C to approximately 50C during a 30-minute exposure to solar radiation. Alternatively, when the leaflets and cuvettes were shielded from solar radiation, leaflet temperature declined to 33C in 10 to 15 minutes. In a second study, 16 horticultural species exhibited a lower variable: maximum fluorescence (F v :F m ) when cuvettes were exposed to solar radiation during the 30-minute dark adaptation than when cuvettes were shielded. In a third study with S. mahagoni, the influence of self-shielding the cuvettes by wrapping them with white tape, white paper, or aluminum foil on temperature and fluorescence was compared to exposing or shielding the entire leaflet and cuvette. All of the shielding methods reduced leaflet temperature and increased the F v :F m ratio compared to leaving cuvettes exposed. These results indicate that heat stress from direct exposure to solar radiation is a potential source of error when interpreting chlorophyll fluorescence measurements on intact leaves. Methods for moderating or minimizing radiation interception during dark adaptation are recommended. (author)

Rapid algal toxicity assay using variable chlorophyll fluorescence for Chlorella kessleri (Chlorophyta)

Czech Academy of Sciences Publication Activity Database

Kvíderová, Jana

2010-01-01

Roč. 25, č. 6 (2010), s. 554-562 ISSN 1520-4081 R&D Projects: GA MŠk 1M0571 Institutional research plan: CEZ:AV0Z60050516 Keywords : bioassay * variable chlorophyll fluorescence * Chlorella kessleri Subject RIV: EF - Botanics Impact factor: 1.932, year: 2010

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. Copyright © 2010 Elsevier Inc. All rights reserved.

A Method of High Throughput Monitoring Crop Physiology Using Chlorophyll Fluorescence and Multispectral Imaging.

Science.gov (United States)

Wang, Heng; Qian, Xiangjie; Zhang, Lan; Xu, Sailong; Li, Haifeng; Xia, Xiaojian; Dai, Liankui; Xu, Liang; Yu, Jingquan; Liu, Xu

2018-01-01

We present a high throughput crop physiology condition monitoring system and corresponding monitoring method. The monitoring system can perform large-area chlorophyll fluorescence imaging and multispectral imaging. The monitoring method can determine the crop current condition continuously and non-destructively. We choose chlorophyll fluorescence parameters and relative reflectance of multispectral as the indicators of crop physiological status. Using tomato as experiment subject, the typical crop physiological stress, such as drought, nutrition deficiency and plant disease can be distinguished by the monitoring method. Furthermore, we have studied the correlation between the physiological indicators and the degree of stress. Besides realizing the continuous monitoring of crop physiology, the monitoring system and method provide the possibility of machine automatic diagnosis of the plant physiology. Highlights: A newly designed high throughput crop physiology monitoring system and the corresponding monitoring method are described in this study. Different types of stress can induce distinct fluorescence and spectral characteristics, which can be used to evaluate the physiological status of plants.

Ultrafast quenching of tryptophan fluorescence in proteins: Interresidue and intrahelical electron transfer

Energy Technology Data Exchange (ETDEWEB)

Qiu Weihong; Li Tanping; Zhang Luyuan; Yang Yi; Kao Yating; Wang Lijuan [Department of Physics, Chemistry, and Biochemistry, Program of Biophysics, Chemical Physics, and Biochemistry, Ohio State University, Columbus, OH 43210 (United States); Zhong Dongping [Department of Physics, Chemistry, and Biochemistry, Program of Biophysics, Chemical Physics, and Biochemistry, Ohio State University, Columbus, OH 43210 (United States)], E-mail: dongping@mps.ohio-state.edu

2008-06-23

Quenching of tryptophan fluorescence in proteins has been critical to the understanding of protein dynamics and enzyme reactions using tryptophan as a molecular optical probe. We report here our systematic examinations of potential quenching residues with more than 40 proteins. With site-directed mutation, we placed tryptophan to desired positions or altered its neighboring residues to screen quenching groups among 20 amino acid residues and of peptide backbones. With femtosecond resolution, we observed the ultrafast quenching dynamics within 100 ps and identified two ultrafast quenching groups, the carbonyl- and sulfur-containing residues. The former is glutamine and glutamate residues and the later is disulfide bond and cysteine residue. The quenching by the peptide-bond carbonyl group as well as other potential residues mostly occurs in longer than 100 ps. These ultrafast quenching dynamics occur at van der Waals distances through intraprotein electron transfer with high directionality. Following optimal molecular orbital overlap, electron jumps from the benzene ring of the indole moiety in a vertical orientation to the LUMO of acceptor quenching residues. Molecular dynamics simulations were invoked to elucidate various correlations of quenching dynamics with separation distances, relative orientations, local fluctuations and reaction heterogeneity. These unique ultrafast quenching pairs, as recently found to extensively occur in high-resolution protein structures, may have significant biological implications.

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...

Convergent preparation and photophysical characterization of dimaleimide dansyl fluorogens: elucidation of the maleimide fluorescence quenching mechanism.

Science.gov (United States)

Guy, Julia; Caron, Karine; Dufresne, Stéphane; Michnick, Stephen W; Skene, W G; Keillor, Jeffrey W

2007-10-03

Dimaleimide fluorogens are being developed for application to fluorescent protein labeling. In this method, fluorophores bearing two maleimide quenching groups do not fluoresce until both maleimide groups have undergone thiol addition reactions with the Cys residues of the target protein sequence [J. Am. Chem. Soc. 2005, 127, 559-566]. In this work, a new convergent synthetic route was developed that would allow any fluorophore to be attached via a linker to a dimaleimide moiety in a modular fashion. Series of dimaleimide and dansyl derivatives were thus prepared conveniently and used to elucidate the mechanism of maleimide quenching. Intersystem crossing was ruled out as a potential quenching pathway, based on the absence of a detectable triplet intermediate by laser flash photolysis. Stern-Volmer rate constants were measured with exogenous dimaleimide quenchers and found to be close to the diffusion-controlled limits, consistent with electron transfer being thermodynamically favorable. The thermodynamic feasibility of the photoinduced electron transfer (PET) quenching mechanism was verified by cyclic voltammetry. The redox potentials measured for dansyl and maleimide confirm that electron transfer from the dansyl excited state to a pendant maleimide group is exergonic and is responsible for fluorescence quenching of the fluorogens studied herein. Taking this PET quenching mechanism into account, future fluorogenic protein labeling agents will be designed with spacers of variable length and rigidity to probe the structure-property PET efficiency relationship.

[Nature of the electron excited state in pigment redox reactions. II. Analysis of the scheme of primary processes in the photooxidation reaction of chlorophylls a and b and pheophytin a ].

Science.gov (United States)

Andreeva, N E; Barashkov, B I; Zakharova, G V; Shubin, V V; Chibisov, A K

1978-01-01

A scheme of primary reactions in photooxidation of pigments was considered assuming that electron transfer processes can occur via singlet excited as well as triplet states. The results of analysis are compared with the experimental data on relative yield values of chlorophylls a, b, and pheophytin a cation-radicals, as well as with the data on fluorescence quenching. A conclusion has been drawn that photooxidation of pigments proceeds exclusively via the triplet state. The dependence of rate constant quenching values of chlorophyll a triplet state by certain electron acceptors on values of half cell potentials was given.

Lettuce flavonoids screening and phenotyping by chlorophyll fluorescence excitation ratio.

Science.gov (United States)

Zivcak, Marek; Brückova, Klaudia; Sytar, Oksana; Brestic, Marian; Olsovska, Katarina; Allakhverdiev, Suleyman I

2017-06-01

Environmentally induced variation and the genotypic differences in flavonoid and phenolic content in lettuce can be reliably detected using the appropriate parameters derived from the records of rapid non-invasive fluorescence technique. The chlorophyll fluorescence excitation ratio method was designed as a rapid and non-invasive tool to estimate the content of UV-absorbing phenolic compounds in plants. Using this technique, we have assessed the dynamics of accumulation of flavonoids related to developmental changes and environmental effects. Moreover, we have tested appropriateness of the method to identify the genotypic differences and fluctuations in total phenolics and flavonoid content in lettuce. Six green and two red genotypes of lettuce (Lactuca sativa L.) grown in pots were exposed to two different environments for 50 days: direct sunlight (UV-exposed) and greenhouse conditions (low UV). The indices based on the measurements of chlorophyll fluorescence after red, green and UV excitation indicated increase of the content of UV-absorbing compounds and anthocyanins in the epidermis of lettuce leaves. In similar, the biochemical analyses performed at the end of the experiment confirmed significantly higher total phenolic and flavonoid content in lettuce plants exposed to direct sun compared to greenhouse conditions and in red compared to green genotypes. As the correlation between the standard fluorescence indices and the biochemical records was negatively influenced by the presence of red genotypes, we proposed the use of a new parameter named Modified Flavonoid Index (MFI) taking into an account both absorbance changes due to flavonol and anthocyanin content, for which the correlation with flavonoid and phenolic content was relatively good. Thus, our results confirmed that the fluorescence excitation ratio method is useful for identifying the major differences in phenolic and flavonoid content in lettuce plants and it can be used for high-throughput pre

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.

Chlorophyll fluorescence imaging accurately quantifies freezing damage and cold acclimation responses in Arabidopsis leaves

Directory of Open Access Journals (Sweden)

Hincha Dirk K

2008-05-01

Full Text Available Abstract Background Freezing tolerance is an important factor in the geographical distribution of plants and strongly influences crop yield. Many plants increase their freezing tolerance during exposure to low, nonfreezing temperatures in a process termed cold acclimation. There is considerable natural variation in the cold acclimation capacity of Arabidopsis that has been used to study the molecular basis of this trait. Accurate methods for the quantitation of freezing damage in leaves that include spatial information about the distribution of damage and the possibility to screen large populations of plants are necessary, but currently not available. In addition, currently used standard methods such as electrolyte leakage assays are very laborious and therefore not easily applicable for large-scale screening purposes. Results We have performed freezing experiments with the Arabidopsis accessions C24 and Tenela, which differ strongly in their freezing tolerance, both before and after cold acclimation. Freezing tolerance of detached leaves was investigated using the well established electrolyte leakage assay as a reference. Chlorophyll fluorescence imaging was used as an alternative method that provides spatial resolution of freezing damage over the leaf area. With both methods, LT50 values (i.e. temperature where 50% damage occurred could be derived as quantitative measures of leaf freezing tolerance. Both methods revealed the expected differences between acclimated and nonacclimated plants and between the two accessions and LT50 values were tightly correlated. However, electrolyte leakage assays consistently yielded higher LT50 values than chlorophyll fluorescence imaging. This was to a large part due to the incubation of leaves for electrolyte leakage measurements in distilled water, which apparently led to secondary damage, while this pre-incubation was not necessary for the chlorophyll fluorescence measurements. Conclusion Chlorophyll

A miniaturized oxygen sensor integrated on fiber surface based on evanescent-wave induced fluorescence quenching

Energy Technology Data Exchange (ETDEWEB)

Xiong, Yan [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, 610500 (China); Tan, Jun; Wang, Chengjie; Zhu, Ying [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Fang, Shenwen [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, 610500 (China); Wu, Jiayi; Wang, Qing [School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Duan, Ming, E-mail: swpua124@126.com [State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500 (China); School of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu 610500 (China); Oil and Gas Field Applied Chemistry Key Laboratory of Sichuan Province, Southwest Petroleum University, Chengdu, 610500 (China)

2016-11-15

In this work, a miniaturized sensor was integrated on fiber surface and developed for oxygen determination through evanescent-wave induced fluorescence quenching. The sensor was designed by using light emitting diode (LED) as light source and optical fiber as light transmission element. Tris(2,2′-bipyridyl) ruthenium ([Ru(bpy){sub 3}]{sup 2+}) fluorophore was immobilized in the organically modified silicates (ORMOSILs) film and coated onto the fiber surface. When light propagated by total internal reflection (TIR) in the fiber core, evanescent wave could be produced on the fiber surface and excite [Ru(bpy){sub 3}]{sup 2+} fluorophore to produce fluorescence emission. Then oxygen could be determinated by its quenching effect on the fluorescence and its concentration could be evaluated according to Stern–Volumer model. Through integrating evanescent wave excitation and fluorescence quenching on fiber surface, the sensor was successfully miniaturized and exhibit improved performances of high sensitivity (1.4), excellent repeatability (1.2%) and fast analysis (12 s) for oxygen determination. The sensor provided a newly portable method for in-situ and real-time measurement of oxygen and showed potential for practical oxygen analysis in different application fields. Furthermore, the fabrication of this sensor provides a miniaturized and portable detection platform for species monitoring by simple modular design. - Highlights: • ORMOSILs sensing film immobilized with [Ru(bpy){sub 3}]{sup 2+} fluorophore was coated on fiber surface. • Evanescent wave on the fiber surface was utilized as excitation source to produce fluorescence. • Oxygen was measured based on its quenching effect on evanescent wave-induce fluorescence. • Sensor fabrication was miniaturized by integrating detection and sensing elements on the fiber. • The modular design sensor provides a detection platform for other species monitoring.

Early Identification of Herbicide Stress in Soybean (Glycine max (L.) Merr.) Using Chlorophyll Fluorescence Imaging Technology.

Science.gov (United States)

Li, Hui; Wang, Pei; Weber, Jonas Felix; Gerhards, Roland

2017-12-22

Herbicides may damage soybean in conventional production systems. Chlorophyll fluorescence imaging technology has been applied to identify herbicide stress in weed species a few days after application. In this study, greenhouse experiments followed by field experiments at five sites were conducted to investigate if the chlorophyll fluorescence imaging is capable of identifying herbicide stress in soybean shortly after application. Measurements were carried out from emergence until the three-to-four-leaf stage of the soybean plants. Results showed that maximal photosystem II (PS II) quantum yield and shoot dry biomass was significantly reduced in soybean by herbicides compared to the untreated control plants. The stress of PS II inhibiting herbicides occurred on the cotyledons of soybean and plants recovered after one week. The stress induced by DOXP synthase-, microtubule assembly-, or cell division-inhibitors was measured from the two-leaf stage until four-leaf stage of soybean. We could demonstrate that the chlorophyll fluorescence imaging technology is capable for detecting herbicide stress in soybean. The system can be applied under both greenhouse and field conditions. This helps farmers to select weed control strategies with less phytotoxicity in soybean and avoid yield losses due to herbicide stress.

[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.

Induction of the 'in vivo' chlorophyll fluorescence excited by CW and pulse-periodical laser radiation

International Nuclear Information System (INIS)

Zakhidov, Eh.A.; Zakhidov, M.A.; Kasymdzhanov, M.A.; Khabibullaev, P.K.

1996-01-01

Inductional changes of fluorescence of the native chlorophyll molecules in plant leaves excited by CW and pulse-periodical laser radiation are studied. The opportunity of controlling of the photosynthesis efficiency through fluorescence response at different rates of the electron flow in charge transfer chain of the photosynthetic apparatus of plant is shown. (author). 13 refs.; 4 refs

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

International Nuclear Information System (INIS)

Friedrich, Leidi C.; Silva, Volnir O.; Quina, Frank H.; Moreira Junior, Paulo F.; Tcacenco, Celize M.

2013-01-01

Aggregation numbers (N 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 (γ = 0.11-0.15, where γ is the slope of a plot of log aggregation number vs. log [Y aq ] and [Y 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 (γ ca. 0.25), a difference attributed to the larger headgroup size of SLES. The I 1 /I 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)

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)

[Effects of drought stress on leaf gas exchange and chlorophyll fluorescence of Salvia miltiorrhiza].

Science.gov (United States)

Luo, Ming-Hua; Hu, Jin-Yao; Wu, Qing-Gui; Yang, Jing-Tian; Su, Zhi-Xian

2010-03-01

Taking the seedlings of Salvia miltiorrhiza cv. Sativa (SA) and S. miltiorrhiza cv. Silcestris (SI) as test materials, this paper studied the effects of drought stress on their leaf gas exchange and chlorophyll fluorescence parameters. After 15 days of drought stress, the net photosynthetic rate (P(n)) and the maximal photochemical efficiency of PS II (F(v)/F(m)) of SA were decreased by 66.42% and 10.98%, whereas those of SI were decreased by 29.32% and 5.47%, respectively, compared with the control, suggesting that drought stress had more obvious effects on the P(n) and F(v)/F(m) of SA than of SI. For SI, the reduction of P, under drought stress was mainly due to stomatal limitation; while for SA, it was mainly due to non-stomatal limitation. Drought led to a decrease of leaf stomatal conductance (G(s)), but induced the increase of water use efficiency (WUE), non-photochemical quenching coefficient (q(N)), and the ratio of photorespiration rate to net photosynthetic rate (P(r)/P(n)), resulting in the enhancement of drought resistance. The increment of WUE, q(N), and P(r)/P(n) was larger for SI than for SA, indicating that SI had a higher drought resistance capacity than SA.

Novel biosensor system model based on fluorescence quenching by a fluorescent streptavidin and carbazole-labeled biotin.

Science.gov (United States)

Zhu, Xianwei; Shinohara, Hiroaki; Miyatake, Ryuta; Hohsaka, Takahiro

2016-10-01

In the present study, a novel molecular biosensor system model was designed by using a couple of the fluorescent unnatural mutant streptavidin and the carbazole-labeled biotin. BODIPY-FL-aminophenylalanine (BFLAF), a fluorescent unnatural amino acid was position-specifically incorporated into Trp120 position of streptavidin by four-base codon method. On the other hand, carbazole-labeled biotin was synthesized as a quencher for the fluorescent Trp120BFLAF mutant streptavidin. The fluorescence of fluorescent Trp120BFLAF mutant streptavidin was decreased as we expected when carbazole-labeled biotin was added into the mutant streptavidin solution. Furthermore, the fluorescence decrease of Trp120BFLAF mutant streptavidin with carbazole-labeled biotin (100 nM) was recovered by the competitive addition of natural biotin. This result demonstrated that by measuring the fluorescence quenching and recovery, a couple of the fluorescent Trp120BFLAF mutant streptavidin and the carbazole-labeled biotin were successfully applicable for quantification of free biotin as a molecular biosensor system. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

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 ...

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.

Fluorescence quenching of 9-cyanoanthracene in presence of zinc tetraphenylporphyrin in a polar liquid medium

International Nuclear Information System (INIS)

Mandal, Paulami; Tiwari, Sanat Kumar; Ganguly, Tapan; Sinha, Subrata

2009-01-01

Steady-state and time-resolved techniques are used to study photoinduced electron and/or excitational energy transfer processes involved within a novel donor (zinc tetraphenylporphyrin)-acceptor (9-cyanoanthracene) system in a polar liquid medium (acetonitrile) at the ambient temperature (300 K). After photoexcitation of 9-cyanoanthracene, its fluorescence emission as well as lifetime are found to be quenched in presence of zinc tetraphenylporphyrin. The fluorescence quenching is ascribed to be due to the combined effect of electron transfer from zinc tetraphenylporphyrin to 9-cyanoanthracene and energy transfer (radiative as well as non-radiative) from 9-cyanoanthracene to zinc tetraphenylporphyrin. The highly exergonic values of Gibbs free energy change for both forward electron transfer reaction (-1.15 eV) and charge recombination reaction (-1.94 eV) indicate the possibilities of occurrences of these two processes in the Marcus inverted region. The fluorescence quenching rate due to photoinduced electron transfer reaction is found to be close to the diffusion-controlled limit within the present donor-acceptor system upon excitation of the acceptor molecules.

Water deficit and salt stress diagnosis through LED induced chlorophyll fluorescence analysis in Jatropha curcas L. oil plants for biodiesel

Science.gov (United States)

Gouveia-Neto, Artur S.; Silva, Elias A., Jr.; Oliveira, Ronaldo A.; Cunha, Patrícia C.; Costa, Ernande B.; Câmara, Terezinha J. R.; Willadino, Lilia G.

2011-02-01

Light-emitting-diode induced chlorophyll fluorescence analysis is employed to investigate the effect of water and salt stress upon the growth process of physicnut(jatropha curcas) grain oil plants for biofuel. Red(Fr) and far-red (FFr) chlorophyll fluorescence emission signals around 685 nm and 735 nm, respectively, were observed and examined as a function of the stress intensity(salt concentration and water deficit) for a period of time of 30 days. The chlorophyll fluorescence(ChlF) ratio Fr/FFr which is a valuable nondestructive and nonintrusive indicator of the chlorophyll content of leaves was exploited to monitor the level of stress experienced by the jatropha plants. The ChlF technique data indicated that salinity plays a minor role in the chlorophyll concentration of leaves tissues for NaCl concentrations in the 25 to 200 mM range, and results agreed quite well with those obtained using conventional destructive spectrophotometric methods. Nevertheless, for higher NaCl concentrations a noticeable decrease in the Chl content was observed. The Chl fluorescence ratio analysis also permitted detection of damage caused by water deficit in the early stages of the plants growing process. A significant variation of the Fr/FFr ratio was observed sample in the first 10 days of the experiment when one compared control and nonwatered samples. The results suggest that the technique may potentially be applied as an early-warning indicator of stress caused by water deficit.

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

OpenAIRE

Friedrich, Leidi C.; Silva, Volnir O.; Moreira Jr, Paulo F.; Tcacenco, Celize M.; Quina, Frank H.

2013-01-01

Aggregation numbers (N 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 40º 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 (γ = 0.11-0.15, where γ is the slope of a plot of log aggregation number vs. log [Yaq] and [Yaq] is the sodium counter...

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

Science.gov (United States)

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

2014-07-01

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

Performance of a two-leaf light use efficiency model for mapping gross primary productivity against remotely sensed sun-induced chlorophyll fluorescence data.

Science.gov (United States)

Zan, Mei; Zhou, Yanlian; Ju, Weimin; Zhang, Yongguang; Zhang, Leiming; Liu, Yibo

2018-02-01

Estimating terrestrial gross primary production is an important task when studying the carbon cycle. In this study, the ability of a two-leaf light use efficiency model to simulate regional gross primary production in China was validated using satellite Global Ozone Monitoring Instrument - 2 sun-induced chlorophyll fluorescence data. The two-leaf light use efficiency model was used to estimate daily gross primary production in China's terrestrial ecosystems with 500-m resolution for the period from 2007 to 2014. Gross primary production simulated with the two-leaf light use efficiency model was resampled to a spatial resolution of 0.5° and then compared with sun-induced chlorophyll fluorescence. During the study period, sun-induced chlorophyll fluorescence and gross primary production simulated by the two-leaf light use efficiency model exhibited similar spatial and temporal patterns in China. The correlation coefficient between sun-induced chlorophyll fluorescence and monthly gross primary production simulated by the two-leaf light use efficiency model was significant (pproduction simulated by the two-leaf light use efficiency model were similar in spring and autumn in most vegetated regions, but dissimilar in winter and summer. The spatial variability of sun-induced chlorophyll fluorescence and gross primary production simulated by the two-leaf light use efficiency model was similar in spring, summer, and autumn. The proportion of spatial variations of sun-induced chlorophyll fluorescence and annual gross primary production simulated by the two-leaf light use efficiency model explained by ranged from 0.76 (2011) to 0.80 (2013) during the study period. Overall, the two-leaf light use efficiency model was capable of capturing spatial and temporal variations in gross primary production in China. However, the model needs further improvement to better simulate gross primary production in summer. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Excited state fluorescence quenching of the U O2++ ion by monovalent anions

International Nuclear Information System (INIS)

Santarine, G.A.

1987-01-01

The reactions of the Uranyl ion U O 2 ++ in the excited state with the monovalent inorganic ions N O 3 - and I O 3 - in aqueous solutions at normal temperature were studied, using three techniques: Fluorescence in the steady state - Flash photolysis - Fluorescence decay after excitation. With increasing concentration of these ions it was observed a decrease in the normalized intensity and a decrease in the decay time of the fluorescence of the Uranyl ion in the solution and a corresponding appearance of the radicals N O 3 . or I O 3 . . In each case the radical was identified by its optical absorption spectrum. These results suggest that the quenching of fluorescence of the Uranyl ion in each case is owing to an electron transfer reaction. In the case of the Nitrate ion the transfer may occur after the formation of an ionic par (U O 2 + ...N O 3 ) in the ground state. Evidence for static quenching in the system Uranyl iodate was not forthcoming. A mechanism for the determination of the velocity constant (probability per ion pair per unit time) is proposed for each of the systems. (author)

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

[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.

Using Quenching to Detect Corrosion on Sculptural Metalwork: A Real-World Application of Fluorescence Spectroscopy

Science.gov (United States)

Hensen, Cory; Clare, Tami Lasseter; Barbera, Jack

2018-01-01

Fluorescence spectroscopy experiments are a frequently taught as part of upper-division teaching laboratories. To expose undergraduate students to an applied fluorescence technique, a corrosion detection method, using quenching, was adapted from authentic research for an instrumental analysis laboratory. In the experiment, students acquire…

Fluorescence Quenching of Humic Acid by Coated Metallic Silver Particles.

Science.gov (United States)

Zhu, Guocheng; Yin, Jun

2017-07-01

Natural organic matter is an important component of the aquatic environments, which has attracted wide attention to its influence of interaction with other pollutants. The present work aimed to investigate its fluorescence quenching (FQ) by coated metallic silver particles (AgNPs). In this work, using fluorescence spectroscopy in conjunction with UV-Vis spectroscopy and dynamic light scattering, the effect of coated AgNPs on fluorescence quenching intensity (FQI) of humic acid (HA) was assessed. In addition, the influence of electrolytes (NaCl, NaNO 3 and CaNO 3 ) in the FQI was observed. Results showed that with AgNPs dosage increased (>1.17X10 -3  mM), fluorescence quantum yield of HA gradually decreased, which implies that the FQ occurred. Furher observation showed that the FQ process followed both first-order and second-order Stern-Volmer functions. The FQ process was affected by the electrolytes: NaCl had an effect on reduction of FQI, possibly resulting from dissolution of AgNPs; Both of NaNO 3 and Ca(NO 3 ) 2 had an effect on the FQ of HA but Ca(NO 3 ) 2 presented greater degree. As a result, the FQ degree of HA by alone electrolyte was listed in descent order as Ca(NO 3 ) 2  > NaNO 3  > NaCl, which also implies the subsequent experimental results, indicating the FQ degree of HA by mutual electrolytes as Ca(NO 3 ) 2  + NaNO 3  > Ca(NO 3 ) 2  + NaCl > NaNO 3  + NaCl.

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

Czech Academy of Sciences Publication Activity Database

Mishra, Kumud; Iannacone, R.; Petrozza, A.; Mishra, Anamika; Armentano, N.; La Vecchia, G.; Trtílek, M.; Cellini, F.; Nedbal, Ladislav

2012-01-01

Roč. 182, SI (2012), s. 79-86 ISSN 0168-9452 R&D Projects: GA MŠk OC08055; GA MŠk 2B06068; GA MŠk(CZ) ED1.1.00/02.0073 Institutional support: RVO:67179843 Keywords : Chlorophyll fluorescence * Drought * High-throughput screening * Solanum lycopersicum * Transcription factor * Transgenic plant Subject RIV: EH - Ecology, Behaviour Impact factor : 2.922, year: 2012

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 temp......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...

Light stress effect and by nitrogen deficiency in plants of Petiveria alliacea measured with two-chlorophyll-fluorescence technique

Science.gov (United States)

Zuluaga, H.; Oviedo, A.; Solarte, Efrain; Pena, E. J.

2004-10-01

The chlorophyll fluorescence was studied in Petiveria alliacea plants exposed to different nitrogen concentrations and light radiation, the response was measured by two different forms; (1) measuring the photosynthetic efficiency with a pulse amplitude modulated fluorometro (PAM) emitted by a 650 nm diode and (2) measuring the fluorescence spectra caused by high power 452 nm diode with a SD2000 spectrometer. It was found out that the photosynthetic efficiency decreased in the plants exposed to high radiance and low nitrogen. Two chlorophyll fluorescence peaks were observed on 684 nm and 739 nm, the intensities in this wavelengths are inversely related with the light radiance. The correlation between the FIR and photosynthetic efficiency was very strong (r2 = -0.809, p Alliacea plants.

Investigation of the fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by certain substituted uracils

Energy Technology Data Exchange (ETDEWEB)

Anbazhagan, V. [School of Chemistry, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu (India); Renganathan, R. [School of Chemistry, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu (India)], E-mail: rrengas@yahoo.com

2009-04-15

The fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by a series of uracils has been studied in water and acetonitrile solvents using steady-state and time-resolved fluorescence techniques. The steady-state fluorescence quenching technique has been performed in three different pHs (i.e. 4, 8 and 12). The bimolecular quenching rate constant (k{sub q}) increases with increase in pH of uracils. In acidic pH, a pure hydrogen atom abstraction is proposed as the quenching mechanism. This is supported by a pronounced solvent deuterium isotope effect. Electron transfer from the anionic form of uracil to the excited state of DBO is proposed as a mechanism for quenching in basic pH on the basis of highly exergonic thermodynamics obtained from the Rehm-Weller equation. The variation of k{sub q} is explained on the basis of the electronic effect of substitution in uracils as well.

Investigation of the fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by certain substituted uracils

International Nuclear Information System (INIS)

Anbazhagan, V.; Renganathan, R.

2009-01-01

The fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by a series of uracils has been studied in water and acetonitrile solvents using steady-state and time-resolved fluorescence techniques. The steady-state fluorescence quenching technique has been performed in three different pHs (i.e. 4, 8 and 12). The bimolecular quenching rate constant (k q ) increases with increase in pH of uracils. In acidic pH, a pure hydrogen atom abstraction is proposed as the quenching mechanism. This is supported by a pronounced solvent deuterium isotope effect. Electron transfer from the anionic form of uracil to the excited state of DBO is proposed as a mechanism for quenching in basic pH on the basis of highly exergonic thermodynamics obtained from the Rehm-Weller equation. The variation of k q is explained on the basis of the electronic effect of substitution in uracils as well

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.

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

Science.gov (United States)

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

2001-01-01

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

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

Science.gov (United States)

García-Sánchez, M A; Serratos, I N; Sosa, R; Tapia-Esquivel, T; González-García, F; Rojas-González, F; Tello-Solís, S R; Palacios-Enriquez, A Y; Esparza Schulz, J M; Arrieta, A

2016-07-22

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 physicochemical

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

Chlorophyll induced fluorescence retrieved from GOME2 for improving gross primary productivity estimates of vegetation

Science.gov (United States)

van Leth, Thomas C.; Verstraeten, Willem W.; Sanders, Abram F. J.

2014-05-01

Mapping terrestrial chlorophyll fluorescence is a crucial activity to obtain information on the functional status of vegetation and to improve estimates of light-use efficiency (LUE) and global primary productivity (GPP). GPP quantifies carbon fixation by plant ecosystems and is therefore an important parameter for budgeting terrestrial carbon cycles. Satellite remote sensing offers an excellent tool for investigating GPP in a spatially explicit fashion across different scales of observation. The GPP estimates, however, still remain largely uncertain due to biotic and abiotic factors that influence plant production. Sun-induced fluorescence has the ability to enhance our knowledge on how environmentally induced changes affect the LUE. This can be linked to optical derived remote sensing parameters thereby reducing the uncertainty in GPP estimates. Satellite measurements provide a relatively new perspective on global sun-induced fluorescence, enabling us to quantify spatial distributions and changes over time. Techniques have recently been developed to retrieve fluorescence emissions from hyperspectral satellite measurements. We use data from the Global Ozone Monitoring Instrument 2 (GOME2) to infer terrestrial fluorescence. The spectral signatures of three basic components atmospheric: absorption, surface reflectance, and fluorescence radiance are separated using reference measurements of non-fluorescent surfaces (desserts, deep oceans and ice) to solve for the atmospheric absorption. An empirically based principal component analysis (PCA) approach is applied similar to that of Joiner et al. (2013, ACP). Here we show our first global maps of the GOME2 retrievals of chlorophyll fluorescence. First results indicate fluorescence distributions that are similar with that obtained by GOSAT and GOME2 as reported by Joiner et al. (2013, ACP), although we find slightly higher values. In view of optimizing the fluorescence retrieval, we will show the effect of the references

SmartFluo: A Method and Affordable Adapter to Measure Chlorophyll a Fluorescence with Smartphones

NARCIS (Netherlands)

Friedrichs, Anna; Busch, Julia; van der Woerd, H.J.; Zielinski, Oliver

2017-01-01

In order to increase the monitoring capabilities of inland and coastal waters, there is a need for new, affordable, sensitive and mobile instruments that could be operated semi-automatically in the field. This paper presents a prototype device to measure chlorophyll a fluorescence: the SmartFluo.

Effects of Different Metals on Photosynthesis: Cadmium and Zinc Affect Chlorophyll Fluorescence in Durum Wheat

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Momchil Paunov

2018-03-01

Full Text Available A comparative study of the effects of exposure to high Cd2+ (50 µM and excess Zn2+ (600 µM on photosynthetic performance of hydroponically-grown durum wheat seedlings was performed. At day 8, Cd and Zn were added to the nutrient solution. After 7-days exposure, the chosen concentrations of both metals resulted in similar relative growth rate (RGR inhibitions of about 50% and comparable retardations of the CO2 assimilation rates (about 30% in the second developed leaf of wheat seedlings. Analysis of chlorophyll a fluorescence indicated that both metals disturbed photosynthetic electron transport processes which led to a 4- to 5-fold suppression of the efficiency of energy transformation in Photosystem II. Non-specific toxic effects of Cd and Zn, which prevailed, were an inactivation of part of Photosystem II reaction centres and their transformation into excitation quenching forms as well as disturbed electron transport in the oxygen-evolving complex. The specificity of the Cd and Zn modes of action was mainly expressed in the intensity of the toxicity effects: despite the similar inhibitions of the CO2 assimilation rates, the wheat photochemistry showed much more sensitivity to Cd than to Zn exposure.

Chlorophyll fluorescence emission can screen cold tolerance of cold acclimated Arabidopsis thaliana accessions

Czech Academy of Sciences Publication Activity Database

Mishra, Anamika; Heyer, A. G.; Mishra, Kumud

2014-01-01

Roč. 10, č. 38 (2014) ISSN 1746-4811 R&D Projects: GA MŠk EE2.3.20.0246; GA MŠk 7E12047 Institutional support: RVO:67179843 Keywords : high-throughput screening * chlorophyll a fluorescence transients * cold tolerance * cold acclimation * whole plant * Arabidopsis thaliana Subject RIV: EH - Ecology, Behaviour Impact factor: 3.102, year: 2014

Chlorophyll fluorescence tracks seasonal variations of photosynthesis from leaf to canopy in a temperate forest.

Science.gov (United States)

Yang, Hualei; Yang, Xi; Zhang, Yongguang; Heskel, Mary A; Lu, Xiaoliang; Munger, J William; Sun, Shucun; Tang, Jianwu

2017-07-01

Accurate estimation of terrestrial gross primary productivity (GPP) remains a challenge despite its importance in the global carbon cycle. Chlorophyll fluorescence (ChlF) has been recently adopted to understand photosynthesis and its response to the environment, particularly with remote sensing data. However, it remains unclear how ChlF and photosynthesis are linked at different spatial scales across the growing season. We examined seasonal relationships between ChlF and photosynthesis at the leaf, canopy, and ecosystem scales and explored how leaf-level ChlF was linked with canopy-scale solar-induced chlorophyll fluorescence (SIF) in a temperate deciduous forest at Harvard Forest, Massachusetts, USA. Our results show that ChlF captured the seasonal variations of photosynthesis with significant linear relationships between ChlF and photosynthesis across the growing season over different spatial scales (R 2  = 0.73, 0.77, and 0.86 at leaf, canopy, and satellite scales, respectively; P chlorophyll content (R 2  = 0.65 for canopy GPP SIF and chlorophyll content; P < 0.0001), leaf area index (LAI) (R 2  = 0.35 for canopy GPP SIF and LAI; P < 0.0001), and normalized difference vegetation index (NDVI) (R 2  = 0.36 for canopy GPP SIF and NDVI; P < 0.0001). Our results suggest that ChlF can be a powerful tool to track photosynthetic rates at leaf, canopy, and ecosystem scales. © 2016 John Wiley & Sons Ltd.

Interactions between iron and titanium metabolism in spinach: A chlorophyll fluorescence study in hydropony

Czech Academy of Sciences Publication Activity Database

Cígler, Petr; Olejníčková, Julie; Hrubý, Martin; Cséfalvay, Ladislav; Peterka, J.; Kužel, S.

2010-01-01

Roč. 167, č. 18 (2010), s. 1592-1597 ISSN 0176-1617 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z40500505; CEZ:AV0Z60870520 Keywords : chlorophyll fluorescence * iron * photosynthetic apparatus * spinach * titanium Subject RIV: CC - Organic Chemistry Impact factor: 2.677, year: 2010

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

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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.

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.

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

International Nuclear Information System (INIS)

Acar, Murat; Bozkurt, Ebru; Meral, Kadem; Arık, Mustafa; Onganer, Yavuz

2015-01-01

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 app ) and the degree of association (α) for C120/CdS NPs were determined as 130.3 M −1 and 0.51 for 4 nm CdS NPs and 624.3 M −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

FluorWPS: A Monte Carlo ray-tracing model to compute sun-induced chlorophyll fluorescence of three-dimensional canopy

Science.gov (United States)

A model to simulate radiative transfer (RT) of sun-induced chlorophyll fluorescence (SIF) of three-dimensional (3-D) canopy, FluorWPS, was proposed and evaluated. The inclusion of fluorescence excitation was implemented with the ‘weight reduction’ and ‘photon spread’ concepts based on Monte Carlo ra...

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. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exciplexes and conical intersections lead to fluorescence quenching in π-stacked dimers of 2-aminopurine with natural purine nucleobases†

Science.gov (United States)

Liang, JingXin; Nguyen, Quynh L.; Matsika, Spiridoula

2016-01-01

Fluorescent analogues of the natural DNA bases are useful in the study of nucleic acids’ structure and dynamics. 2-Aminopurine (2AP) is a widely used analogue with environmentally sensitive fluorescence behavior. The quantum yield of 2AP has been found to be significantly decreased when engaged in π-stacking interactions with the native bases. We present a theoretical study on fluorescence quenching mechanisms in dimers of 2AP π-stacked with adenine or guanine as in natural DNA. Relaxation pathways on the potential energy surfaces of the first excited states have been computed and reveal the importance of exciplexes and conical intersections in the fluorescence quenching process. PMID:23625036

Numerical simulation of dynamic quenching of dual-split fluorescence of molecules with intramolecular hydrogen bonds

International Nuclear Information System (INIS)

Morozov, V.A.; Chuvulkin, N.D.; Smolenskij, E.A.; Dubina, Yu.M.

2014-01-01

The dynamic quenching of intensity pulses of the dual-split fluorescence (DSF) has been simulated using numerical solutions of the equations for the population matrix of five states of the model fluorescent molecule (FM). The state with the highest energy is considered as resonantly excited by irradiation, and two other excited states populated by subsequent relaxation processes are taken as initial states for the FM transitions with emission of the DSF photons. The FM model parameters are selected to fit typical parameters of the molecules with intramolecular proton photo transfer. Quenching is considered as a consequence of non-radiative decay of the FM excited states due to collisions with the quencher molecules. Examples of two types of the DSF quenching of the FM are given. The first type leads to an intramolecular radiationless decay of particular excited states of the FM, and the second one results in radiationless transitions from the same states to the quencher molecule states. (authors)

An interaction of the functionalized closo-borates with albumins: The protein fluorescence quenching and calorimetry study

International Nuclear Information System (INIS)

Losytskyy, Mykhaylo Yu.; Kovalska, Vladyslava B.; Varzatskii, Oleg A.; Kuperman, Marina V.; Potocki, Slawomir; Gumienna-Kontecka, Elzbieta; Zhdanov, Andrey P.; Yarmoluk, Sergiy M.; Voloshin, Yan Z.; Zhizhin, Konstantin Yu.; Kuznetsov, Nikolai T.; Elskaya, Anna V.

2016-01-01

An interaction of the boron clusters closo-borates K 2 [B 10 H 10 ], K 2 [B 12 H 12 ] and their functionalized derivatives with serum proteins human (HSA) and bovine (BSA) albumins and immonoglobulin IgG as well as globular proteins β-lactoglobulin and lysozyme was characterized. The steady state and time resolved protein fluorescence quenching studies point on the binding of the closo-borate arylamine derivatives to serum albumins and discrimination of other proteins. The mechanism of the albumin fluorescence quenching by the closo-borate arylamine derivatives was proposed. The complex formation between albumin and the closo-borate molecules has been confirmed by isothermal titration calorimetry (ITC). The compound (K 2 [B 10 H 10 ]) and its arylamine derivative both interact with HSA, have close values of K a (1.4 and 1.2×10 3 M −1 respectively) and Gibbs energy (−17.9 and −17.5 kJ/mol respectively). However, the arylamine derivative forms complex with the higher guest/host binding ratio (4:1) comparing to the parent closo-borate (2:1). - Highlights: • Complex formation between boron clusters closo-borates and albumins was confirmed. • Functional substituent of closo-borate strongly affects its complex with albumins. • Binding of arylamine closo-borates essentially quench the albumin fluorescence. • Mechanism of tryptophan emission quenching by arylamine closo-borates was proposed.

Test and Control System for Chlorophyll Fluorescence Parameters Using LED as Excitation Source

Directory of Open Access Journals (Sweden)

Zou Qiuying

2014-05-01

Full Text Available A new scheme on test and control system for chlorophyll fluorescence is presented in this work, which uses light-emitting diode (LED excitation by means of measuring the fluorescence parameter fpsII. The system takes programmable power supply as LEDs illumination drive power with high sensitivity and signal-to-noise ratio. MINIPAM is used to measure fluorescence parameter fpsII and keeps communication with upper PC by serial port. The upper PC can control the power supply and process the data received from MINIPAM by software which is programmed in VB6. The results show that the system has a lot of advantages such as high accuracy and convenience. The effect of environmental factors on fluorescence parameters is analyzed comprehensively. It will be a practical measurement and control system for photosynthetic ability and have wide application foreground.

Selective fluorescence quenching of nitrogen-containing polycyclic aromatic hydrocarbons by aliphatic amines

International Nuclear Information System (INIS)

Li Xiaoping; McGuffin, Victoria L.

2004-01-01

In this investigation, primary, secondary, and tertiary amines are evaluated for their efficiency and selectivity as fluorescence quenchers for polycyclic aromatic hydrocarbons (PAHs) and nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs). In general, the quenching efficiency tends to increase from primary to tertiary amine due to a greater number of alkyl groups that increase the electron-donating ability. However, the selectivity decreases from primary to tertiary amine. The effect of low concentrations of water is also examined. Because water can form hydrogen bonds with amines, the nonbonding electron pair is not available for interaction with the fluorophore, thus the quenching constant is decreased. These aliphatic amines are then applied to PAHs and N-PAHs and some interesting trends are observed. Whereas amino-PAHs remain virtually unquenched by different amines, aza-PAHs are all quenched well. The selectivity between aza-PAHs and amino-PAHs is as high as several hundred. This trend provides an easy and effective method to discriminate between these classes of N-PAHs. Moreover, the alternant aza-PAHs are quenched more than their corresponding alternant PAHs

Chlorophyll fluorescence emission as a reporter on cold tolerance in Arabidopsis thaliana accessions

Czech Academy of Sciences Publication Activity Database

Mishra, Anamika; Mishra, Kumud; Höermiller, I. I.; Heyer, A. G.; Nedbal, Ladislav

2011-01-01

Roč. 6, č. 2 (2011), s. 301-310 ISSN 1559-2316 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073; GA MŠk OC08055; GA MŠk 2B06068 Institutional research plan: CEZ:AV0Z60870520 Keywords : chlorophyll fluorescence * cold acclimation * electrolyte leakage * high - throughput screening * natural accessions Subject RIV: EH - Ecology, Behaviour

Computer Reconstruction of Plant Growth and Chlorophyll Fluorescence Emission in Three Spatial Dimensions

Czech Academy of Sciences Publication Activity Database

Bellasio, Ch.; Olejníčková, Julie; Tesař, R.; Šebela, David; Nedbal, Ladislav

2012-01-01

Roč. 12, č. 1 (2012), s. 1052-1071 ISSN 1424-8220 R&D Projects: GA ČR GA522/09/1565; GA MŠk(CZ) ED1.1.00/02.0073 Institutional support: RVO:67179843 Keywords : 3D reconstruction * chlorophyll fluorescence imaging * leaf area * leaf angle * plant growth * coded light Subject RIV: EH - Ecology, Behaviour Impact factor: 1.953, year: 2012

N-acetylcysteine induced quenching of red fluorescent oligonucleotide-stabilized silver nanoclusters and the application in pharmaceutical detection

International Nuclear Information System (INIS)

Wang, Xinyi; Lin, Ruoyun; Xu, Zhihan; Huang, Hongduan; Li, Limei; Liu, Feng; Li, Na; Yang, Xiaoda

2013-01-01

Graphical abstract: -- Highlights: •A new method for nanomolar NAC determination with LOD of 50 nM was reported. •The combined mechanism for NAC quenching with static dominating was suggested. •DNA-Ag NC structure changed with addition of NAC, proved by spectroscopic studies. -- Abstract: In this work, we reported a new, simple and sensitive method for determination of N-acetylcysteine (NAC) based on quenching of the red fluorescence of oligonuleotide-protected silver nanoculsters (Ag NCs) with the quantum yield of 68.3 ± 0.3%. This method was successfully used for the assay of NAC granules presenting a linear range from 100 nM to 1200 nM (LOD of 50 nM) with minimal interferences from potential coexisting substances. It is for the first time that quenching performance of the thiol-containing compound was found to follow a non-linear Stern–Volmer profile, indicative of a complicated quenching mechanism with static quenching dominating, in which DNA-template of Ag NCs was partly replaced by NAC, as elucidated by spectral investigations. This study extended the analytical application of silver nanoclusters as well as provided a more insightful understanding of the quenching mechanism of thiol-compounds on the fluorescence of Ag NCs

Sensitive detection of alkaline phosphatase by switching on gold nanoclusters fluorescence quenched by pyridoxal phosphate.

Science.gov (United States)

Halawa, Mohamed Ibrahim; Gao, Wenyue; Saqib, Muhammad; Kitte, Shimeles Addisu; Wu, Fengxia; Xu, Guobao

2017-09-15

In this work, we designed highly sensitive and selective luminescent detection method for alkaline phosphatase using bovine serum albumin functionalized gold nanoclusters (BSA-AuNCs) as the nanosensor probe and pyridoxal phosphate as the substrate of alkaline phosphatase. We found that pyridoxal phosphate can quench the fluorescence of BSA-AuNCs and pyridoxal has little effect on the fluorescence of BSA-AuNCs. The proposed mechanism of fluorescence quenching by PLP was explored on the basis of data obtained from high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), UV-vis spectrophotometry, fluorescence spectroscopy, fluorescence decay time measurements and circular dichroism (CD) spectroscopy. Alkaline phosphatase catalyzes the hydrolysis of pyridoxal phosphate to generate pyridoxal, restoring the fluorescence of BSA-AuNCs. Therefore, a recovery type approach has been developed for the sensitive detection of alkaline phosphatase in the range of 1.0-200.0U/L (R 2 =0.995) with a detection limit of 0.05U/L. The proposed sensor exhibit excellent selectivity among various enzymes, such as glucose oxidase, lysozyme, trypsin, papain, and pepsin. The present switch-on fluorescence sensing strategy for alkaline phosphatase was successfully applied in human serum plasma with good recoveries (100.60-104.46%), revealing that this nanosensor probe is a promising tool for ALP detection. Copyright © 2017 Elsevier B.V. All rights reserved.

Heavy atom induced room temperature fluorescence quenching of PAH from a glucose glass

Energy Technology Data Exchange (ETDEWEB)

Marlow, Matt, E-mail: matthew.marlow@nicholls.edu

2017-06-15

Sugar glasses are a relatively new matrix for solid-matrix luminescence. Molecular interactions within the sugar glass are not well understood. Fluorescence quenching was used to investigate molecular interactions within the sugar glass matrix. The room temperature fluorescence quenching of pyrene and naphthalene was observed from a glucose glass. The heavy atom salt NaI was the quencher. Two solvent compositions 50/50 and 60/40 MeOH/water, used for glass preparation, were examined for their effect on glass rigidity and molecular interactions. A complex static mechanism was observed for glasses prepared with 50/50 MeOH/water. This data was fit to the sphere of action model and associations constants determined. A Stern-Volmer static mechanism of quenching was observed for glasses prepared with 60/40 MeOH/water. This data fit the Stern-Volmer equation and association constants were determined. A larger association constant was observed for pyrene compared to naphthalene for both solvent systems used. Pyrene had a larger association constant with a sugar glass prepared with 60/40 MeOH/water compared to 50/50 MeOH/water implying a greater association between pyrene and iodide. The greater association is a reflection of a more rigid internal environment for the sugar glass prepared with 60/40 MeOH/water.

On the sub-maximal yield and photo-electric stimulation of chlorophyll a fluorescence in single turnover excitations in plant cells

NARCIS (Netherlands)

Vredenberg, W.J.; Rensen, van J.J.S.; Rodrigues, G.C.

2006-01-01

A set of expressions is derived which quantifies the chlorophyll fluorescence yield in terms of rate constants of primary light reactions of PSII, the fraction of open and semi-open RCs and of the electric field sensed by the RC in the thylakoid membrane. The decay kinetics of the chlorophyll

Hydrogen bond strengthening induces fluorescence quenching of PRODAN derivative by turning on twisted intramolecular charge transfer

Science.gov (United States)

Yang, Yonggang; Li, Donglin; Li, Chaozheng; Liu, YuFang; Jiang, Kai

2017-12-01

Researchers have proposed different effective mechanisms of hydrogen bonding (HB) on the fluorescence of 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and its derivatives. Herein, excited state transition and dynamics analysis confirm that the fluorescence of PD (a derivative of PRODAN with ethyl replaced by 3-hydroxy-2,2-dimethylpropan) emits from the planar intramolecular charge transfer (PICT) state rather than twist ICT (TICT) state, because the fluorescence emission and surface hopping from the TICT state to the twist ground (T-S0) state is energy forbidden. Nevertheless, the strengthening of intramolecular-HB (intra-HB) and intermolecular-HB (inter-HB) of PD-(methanol)2 smooth the pathway of surface hopping from TICT to T-S0 state and the external conversion going to planar ground state by decreasing the energy difference of the two states. This smoothing changes the fluorescence state of PD-(methanol)2 to the TICT state in which fluorescence emission does not occur but surface hopping, leading to the partial fluorescence quenching of PD in methanol solvent. This conclusion is different from previous related reports. Moreover, the inter-HB strengthening of PD-methanol in PICT state induces the cleavage of intra-HB and a fluorescence red-shift of 54 nm compared to PD. This red-shift increases to 66 nm for PD-(methanol)2 for the strengthening of the one intra-HB and two inter-HBs. The dipole moments of PD-methanol and PD-(methanol)2 respectively increase about 10.3D and 8.1D in PICT state compared to PD. The synergistic effect of intra-HB and inter-HB induces partial quenching of PD in methanol solvent by turning on the TICT state and fluorescence red-shift. This work gives a reasonable description on the fluorescence red-shift and partial quenching of PD in methanol solvent, which will bring insight into the study of spectroscopic properties of molecules owning better spectral characteristics.

The Effect of PSII Inhibitors on Kautsky Curve and Chlorophyll Fluorescence in Common Lambsquarters (Chenopodium album L. and Common Purslane (Portulaca oleracea L.

Directory of Open Access Journals (Sweden)

A.A. Chitband

2016-03-01

Full Text Available Introduction: Desmedipham + phenmedipham + ethofumesate, phenylcarbamates + benzofuranyl alkanesulfonate herbicides, is widely used for post-emergence broad-leaved weed control in sugar beet. Chloridazon, a pyridazinone herbicide, is used as a pre- and post- emergence herbicide in sugar beet. Desmedipham, phenmedipham and chloridazon, are photosystem II (PSII inhibitors, their translocation via xylem are slow, mostly absorbed not only by roots, but also by foliage. Their mode of action is through the blocking of electron transfer between the primary and secondary quinones (QA and QB of PSII by binding to the QB-binding site and accepting electrons from QA in the chloroplasts. Measures of changes to the chlorophyll fluorescence induction curve (Kautsky curve, is a rapid, non-invasive and simple method for monitoring the physiological status of the photosynthetic apparatus in the plant. There are three phases found on the O, J, I and P steps. These phases primarily point out photochemical events relevant to PSII. The three phases are described as follows: at the O-J phase complete reduction of the primary electron acceptor QA of PSII takes place from 50 μs to 2 ms, the J-I phase corresponds to electron transfer from QA to QB happens between 2 to 30 ms and the I-P phase corresponds to the release of fluorescence quenching by the oxidized plastoquinone pool taking place within 30-500 ms. Materials and Methods: In order to determine how exposure affects the fluorescence induction curve (Kautsky curve and its parameters, two dose-response experiments carried out for chlorophyll fluorescence measuring. The treatments involved desmedipham + phenmedipham + ethofumesate at 0, 51.38, 102.75, 205.5, 308.25, 411, 616.5 and 822 g a.i. ha-1 and chloridazon at 0, 81.25, 162.5, 325, 650, 1300, 1950 and 2600 g a.i. ha-1 on common lambsquarters (Chenopodium album L. and common purslane (Portulaca oleracea L. at the research glasshouse of Agricultural Faculty of

An interaction of the functionalized closo-borates with albumins: The protein fluorescence quenching and calorimetry study

Energy Technology Data Exchange (ETDEWEB)

Losytskyy, Mykhaylo Yu., E-mail: mlosytskyy@gmail.com [Institute of Molecular Biology and Genetics, NASU, 150 Zabolotnogo Street, 03143 Kyiv (Ukraine); Kovalska, Vladyslava B. [Institute of Molecular Biology and Genetics, NASU, 150 Zabolotnogo Street, 03143 Kyiv (Ukraine); Varzatskii, Oleg A. [V. I. Vernadsky Institute of General and Inorganic Chemistry, 32/34 Palladin Avenue, 03080 Kyiv (Ukraine); Kuperman, Marina V. [Institute of Molecular Biology and Genetics, NASU, 150 Zabolotnogo Street, 03143 Kyiv (Ukraine); Potocki, Slawomir; Gumienna-Kontecka, Elzbieta [Faculty of Chemistry, Wroclaw University, 14F. Joliot-Curie Street, 50-383 Wroclaw (Poland); Zhdanov, Andrey P. [Kurnakov Institute of General and Inorganic Chemistry, 31 Leninskii Avenue, 119991 Moscow (Russian Federation); Yarmoluk, Sergiy M. [Institute of Molecular Biology and Genetics, NASU, 150 Zabolotnogo Street, 03143 Kyiv (Ukraine); Voloshin, Yan Z. [Nesmeyanov Institute of Organoelement Compounds, 28 Vavilova Street, 119991 Moscow (Russian Federation); Zhizhin, Konstantin Yu.; Kuznetsov, Nikolai T. [Kurnakov Institute of General and Inorganic Chemistry, 31 Leninskii Avenue, 119991 Moscow (Russian Federation); Elskaya, Anna V. [Institute of Molecular Biology and Genetics, NASU, 150 Zabolotnogo Street, 03143 Kyiv (Ukraine)

2016-01-15

An interaction of the boron clusters closo-borates K{sub 2}[B{sub 10}H{sub 10}], K{sub 2}[B{sub 12}H{sub 12}] and their functionalized derivatives with serum proteins human (HSA) and bovine (BSA) albumins and immonoglobulin IgG as well as globular proteins β-lactoglobulin and lysozyme was characterized. The steady state and time resolved protein fluorescence quenching studies point on the binding of the closo-borate arylamine derivatives to serum albumins and discrimination of other proteins. The mechanism of the albumin fluorescence quenching by the closo-borate arylamine derivatives was proposed. The complex formation between albumin and the closo-borate molecules has been confirmed by isothermal titration calorimetry (ITC). The compound (K{sub 2}[B{sub 10}H{sub 10}]) and its arylamine derivative both interact with HSA, have close values of K{sub a} (1.4 and 1.2×10{sup 3} M{sup −1} respectively) and Gibbs energy (−17.9 and −17.5 kJ/mol respectively). However, the arylamine derivative forms complex with the higher guest/host binding ratio (4:1) comparing to the parent closo-borate (2:1). - Highlights: • Complex formation between boron clusters closo-borates and albumins was confirmed. • Functional substituent of closo-borate strongly affects its complex with albumins. • Binding of arylamine closo-borates essentially quench the albumin fluorescence. • Mechanism of tryptophan emission quenching by arylamine closo-borates was proposed.

Determination of selenium via the fluorescence quenching effect of selenium on hemoglobin-catalyzed peroxidative reaction.

Science.gov (United States)

Chen, Ya-Hong; Zhang, Ya-Nan; Tian, Feng-Shou

2015-05-01

A new method for the determination of selenium based on its fluorescence quenching on the hemoglobin-catalyzed reaction of H2 O2 and l-tyrosine has been established. The effect of pH, foreign ions and the optimization of variables on the determination of selenium was examined. The calibration curve was found to be linear between the fluorescence quenching (F0 /F) and the concentration of selenium within the range of 0.16-4.00 µg/mL. The detection limit was 1.96 ng/mL and the relative standard deviation was 3.14%. This method can be used for the determination of selenium in Se-enriched garlic bulbs with satisfactory results. Copyright © 2014 John Wiley & Sons, Ltd.

Red shift in the spectrum of a chlorophyll species is essential for the drought-induced dissipation of excess light energy in a poikilohydric moss, Bryum argenteum.

Science.gov (United States)

Shibata, Yutaka; Mohamed, Ahmed; Taniyama, Koichiro; Kanatani, Kentaro; Kosugi, Makiko; Fukumura, Hiroshi

2018-05-01

Some mosses are extremely tolerant of drought stress. Their high drought tolerance relies on their ability to effectively dissipate absorbed light energy to heat under dry conditions. The energy dissipation mechanism in a drought-tolerant moss, Bryum argenteum, has been investigated using low-temperature picosecond time-resolved fluorescence spectroscopy. The results are compared between moss thalli samples harvested in Antarctica and in Japan. Both samples show almost the same quenching properties, suggesting an identical drought tolerance mechanism for the same species with two completely different habitats. A global target analysis was applied to a large set of data on the fluorescence-quenching dynamics for the 430-nm (chlorophyll-a selective) and 460-nm (chlorophyll-b and carotenoid selective) excitations in the temperature region from 5 to 77 K. This analysis strongly suggested that the quencher is formed in the major peripheral antenna of photosystem II, whose emission spectrum is significantly broadened and red-shifted in its quenched form. Two emission components at around 717 and 725 nm were assigned to photosystem I (PS I). The former component at around 717 nm is mildly quenched and probably bound to the PS I core complex, while the latter at around 725 nm is probably bound to the light-harvesting complex. The dehydration treatment caused a blue shift of the PS I emission peak via reduction of the exciton energy flow to the pigment responsible for the 725 nm band.

Determination of trace aluminum by fluorescence quenching method based on catalysis of potassium chlorate oxidizing alizarin red

Science.gov (United States)

Shao-Qin, Lin; Xuan, Lin; Shi-Rong, Hu; Li-Qing, Zeng; Yan, Wang; Li, Chen; Jia-Ming, Liu; Long-Di, Li

2005-11-01

A new method for the determination of trace aluminum has been proposed. It is based on the fact that alizarin red can emit strong and stable fluorescence at 80 °C for 30 min and Al 3+ can effectively catalyze potassium chlorate oxidizing alizarin red to form non-fluorescence complex which cause the fluorescence quenching. The linear dynamic range of this method is 0.040-4.00 ng l -1 with a detection limit of 5.3 pg l -1. The regression equation can be expressed as Δ If = 8.731 + 21.73 c (ng l -1), with the correlation coefficient r = 0.9992 ( n = 6). This sensitive, rapid and accurate method has been applied to the determination of trace aluminum(III) in human hair and tea samples successfully. What is more, the mechanism of catalyzing potassium chlorate oxidizing alizarin red by the fluorescence quenching method is also discussed.

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.

A sensitive fluorescence quenching method for the detection of tartrazine with acriflavine in soft drinks.

Science.gov (United States)

Yang, Huan; Ran, Guihua; Yan, Jingjing; Zhang, Hui; Hu, Xiaoli

2018-03-01

In this work, a simple, rapid, sensitive, selective spectrofluorimetric method was applied to detect tartrazine. The fluorescence of acriflavine could be efficiently quenched by tartrazine. The method manifested real time response as well as presented satisfied linear relationship to tartrazine. The linear response range of tartrazine (R 2 = 0.9995) was from 0.056 to 5 μmol L -1 . The detection limit (3σ/k) was 0.017 μmol L -1 , indicating that this method could be applied to detect traces of tartrazine. The accuracy and precision of the method was further assured by recovery studies via a standard addition method, with percentage recoveries in the range of 96.0% to 103.0%. Moreover, a quenching mechanism was investigated systematically by the linear plots at varying temperatures based on the Stern-Volmer equation, fluorescence lifetime and UV-visible absorption spectra, all of which proved to be static quenching. This sensitive, selective assay possessed a great application prospect for the food industry owing to its simplicity and rapidity for the detection of tartrazine. Copyright © 2017 John Wiley & Sons, Ltd.

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.

Steady-state chlorophyll fluorescence (Fs) as a tool to monitor plant heat and drought stress

Science.gov (United States)

Cendrero Mateo, M.; Carmo-Silva, A.; Salvucci, M.; Moran, S. M.; Hernandez, M.

2012-12-01

Crop yield decreases when photosynthesis is limited by heat or drought conditions. Yet farmers do not monitor crop photosynthesis because it is difficult to measure at the field scale in real time. Steady-state chlorophyll fluorescence (Fs) can be used at the field level as an indirect measure of photosynthetic activity in both healthy and physiologically-perturbed vegetation. In addition, Fs can be measured by satellite-based sensors on a regular basis over large agricultural regions. In this study, plants of Camelina sativa grown under controlled conditions were subjected to heat and drought stress. Gas exchange and Fs were measured simultaneously with a portable photosynthesis system under light limiting and saturating conditions. Results showed that Fs was directly correlated with net CO2 assimilation (A) and inversely correlated with non-photochemical quenching (NPQ). Analysis of the relationship between Fs and Photosynthetically Active Radiation (PAR) revealed significant differences between control and stressed plants that could be used to track the status, resilience, and recovery of photochemical processes. In summary, the results provide evidence that Fs measurements, even without normalization, are an easy means to monitor changes in plant photosynthesis, and therefore, provide a rapid assessment of plant stress to guide farmers in resource applications. Figure1. Net CO2 assimilation rate (A) of Camelina sativa plants under control conditions and after heat stress exposure for 1 or 3 days (1d-HS and 3d-HS, respectively) (right) and control, drought and re-watering conditions (left). Conditions for infra-red gas analysis were: reference CO2 = 380 μmol mol-1, PPFD = 500 μmol m-2 s-1 and Tleaf set to 25°C (control, drought and re-water) or 35°C (HS). Different letters denote significant differences at the α=0.05 level. Values are means±SEM (n=10). Figure 2. Stable chlorophyll fluorescence (Fs) of Camelina sativa plants under control conditions and

Plant Chlorophyll fluorescence: active and passive measurements at canopy and leaf scales with different nitrogen treatments

Science.gov (United States)

Most studies assessing chlorophyll fluorescence (ChlF) have examined leaf responses to environmental stress conditions using active techniques. Alternatively, passive techniques are able to measure ChlF at both leaf and canopy scales. However, although the measurement principles of both techniques a...

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. Copyright © 2014 Elsevier B.V. All rights reserved.

Sun-induced chlorophyll fluorescence, photosynthesis, and light use efficiency of a soybean field from seasonally continuous measurements

Science.gov (United States)

Recent development of sun-induced chlorophyll fluorescence (SIF) technology is stimulating studies to remotely approximate canopy photosynthesis (measured as gross primary production, GPP). While multiple applications have advanced the empirical relationship between GPP and SIF, mechanistic understa...

Fluorescence turn-on detection of target sequence DNA based on silicon nanodot-mediated quenching.

Science.gov (United States)

Zhang, Yanan; Ning, Xinping; Mao, Guobin; Ji, Xinghu; He, Zhike

2018-05-01

We have developed a new enzyme-free method for target sequence DNA detection based on the dynamic quenching of fluorescent silicon nanodots (SiNDs) toward Cy5-tagged DNA probe. Fascinatingly, the water-soluble SiNDs can quench the fluorescence of cyanine (Cy5) in Cy5-tagged DNA probe in homogeneous solution, and the fluorescence of Cy5-tagged DNA probe can be restored in the presence of target sequence DNA (the synthetic target miRNA-27a). Based on this phenomenon, a SiND-featured fluorescent sensor has been constructed for "turn-on" detection of the synthetic target miRNA-27a for the first time. This newly developed approach possesses the merits of low cost, simple design, and convenient operation since no enzymatic reaction, toxic reagents, or separation procedures are involved. The established method achieves a detection limit of 0.16 nM, and the relative standard deviation of this method is 9% (1 nM, n = 5). The linear range is 0.5-20 nM, and the recoveries in spiked human fluids are in the range of 90-122%. This protocol provides a new tactic in the development of the nonenzymic miRNA biosensors and opens a promising avenue for early diagnosis of miRNA-associated disease. Graphical abstract The SiND-based fluorescent sensor for detection of S-miR-27a.

Determination of copper (II) in foodstuffs based on its quenching effect on the fluorescence of N,N'-bis(pyridoxal phosphate)-o-phenylenediamine.

Science.gov (United States)

Xu, Canhui; Liao, Lifu; He, Yunfei; Wu, Rurong; Li, Shijun; Yang, Yanyan

2015-01-01

A Schiff base-type fluorescence probe was prepared for the detection of copper (II) in foodstuffs. The probe is N,N'-bis(pyridoxal phosphate)-o-phenylenediamine (BPPP). It was synthesized by utilizing the Schiff base condensation reaction of pyridoxal 5-phosphate with 1,2-phenylenediamine. BPPP has the properties of high fluorescence stability, good water solubility and low toxicity. Its maximum excitation wavelength and maximum fluorescence emission wavelength are at 389 and 448 nm, respectively. When BPPP coexists with copper (II), its fluorescence is dramatically quenched. Under a certain condition, the fluorescence intensity decreased proportionally to the concentration of copper (II) by the quenching effect. Based on this fact, we established a fluorescence quenching method for the determination of copper (II). Under optimal conditions a linear range was found to be 0.5-50 ng/mL with a detection limit of 0.2 ng/mL. The method has been applied to determine copper (II) in foodstuff samples and the analytical results show good agreement with that obtained from atomic absorption spectrometry method. Copyright © 2015 Elsevier B.V. All rights reserved.

Uptake of diuron and concomitant loss of photosynthetic activity in leaves as visualized by imaging the red chlorophyll fluorescence.

Science.gov (United States)

Lichtenthaler, Hartmut K; Langsdorf, Gabriele; Buschmann, Claus

2013-10-01

The principles of the chlorophyll (Chl) fluorescence induction kinetics (known as Kautsky effect) and their change by the photosystem II herbicide diuron are presented together with the Chl fluorescence emission spectra of a normal and diuron-inhibited leaf. By imaging the Chl fluorescence emission of green leaves the successive uptake of diuron and the concomitant loss of photosynthetic quantum conversion from the leaf base to the leaf tip are documented.

Meta-analysis assessing potential of steady-state chlorophyll fluorescence for remote sensing detection of plant water, temperature and nitrogen stress

Czech Academy of Sciences Publication Activity Database

Ač, Alexander; Malenovský, Z.; Olejníčková, Julie; Gallé, A.; Rascher, U.; Mohammed, G.

2015-01-01

Roč. 168, oct (2015), s. 420-436 ISSN 0034-4257 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : steady-state chlorophyll fluorescence * passive sun-induced fluorescence * active laser-induced fluorescence * photosynthesis * stress * water * temperature * nitrogen * random-effects meta-analysis * FLEX satellite mission Subject RIV: EH - Ecology, Behaviour Impact factor: 5.881, year: 2015

Investigations on the fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene by certain flavonoids.

Science.gov (United States)

Anbazhagan, V; Kalaiselvan, A; Jaccob, M; Venuvanalingam, P; Renganathan, R

2008-05-29

The fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by seven flavonoids namely flavone, flavanone, quercetin, rutin, genistein, diadzein and chrysin has been investigated in acetonitrile and dichloromethane solvents. The bimolecular quenching rate constants lie in the range of 0.09-5.75 x 10(9)M(-1)s(-1) and are explained in terms of structure of the flavonoids studied. The reactivity of flavonoids are in the order: quercetin>rutin>genistein>diadzein>chrysin>flavone>flavanone. The quenching rate constants (k(q)) increase with increase in the number of -OH groups. The endergonic thermodynamic values of DeltaG(et) reveal that electron transfer quenching mechanism can be ruled out. Bond dissociation enthalpy calculations reveal that the position of -OH is important. Further in vitro-antioxidant activities of flavonoids were evaluated with rat liver catalase by gel electrophoresis. The deuterium isotope effect thus observed in this work provides evidence for hydrogen abstraction involved in the quenching process of singlet excited DBO by flavonoids. The data suggest the involvement of direct hydrogen atom transfer (radical scavenging) in the fluorescence quenching of DBO. Bond dissociation enthalpy calculation performed at B3LYP/6-31G(p')//B3LYP/3-21G level are in excellent agreement with the above observations and further reveal that the number OH groups and position of them decide the quenching ability of the flavonoids.

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

NARCIS (Netherlands)

Vredenberg, W.J.; Kasalicky, V.; Durchan, M.; Prasil, O.

2006-01-01

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

Study of 660 nm laser-induced photoluminescence of chlorophyll-a and its applications

International Nuclear Information System (INIS)

Song, Y; Zhang, D X; Zhang, H J

2007-01-01

Based on the phenomenon of chlorophyll a photoluminescence, this paper introduces a new method to measure the chlorophyll a content, using 660nm laser diode as a new kind of light source to stimulate fluorescence as well as combining a fiber and spectrum technique. We analyze the characteristics of laser-induced fluorescence spectrum of chlorophyll a and then put forward the new method using two parameters, the relative fluorescence intensity and fluorescence intensity ratio F685/F735, to measure the chlorophyll a content in the water and green leaves respectively. The experimental results indicate that it is completely feasible to give a visual judgment for chlorophyll a content, according to the fluorescence emission spectrum of chlorophyll a. Subsequently, it is verified by three kinds of typical applications. All of these provide a new kind of light source to develop the chlorophyll a fluorometry and further give a technical foundation of on-spot monitoring the chlorophyll a content in the ocean or in green leaves

Simultaneous presence of dynamic and sphere action component in the fluorescence quenching of human serum albumin by diphthaloylmaslinic acid

Energy Technology Data Exchange (ETDEWEB)

Molina-Bolívar, J.A., E-mail: jmb@uma.es [Departamento de Física Aplicada II, Escuela de Ingenierías, Universidad de Málaga, Campus de Teatinos, 29071, Málaga (Spain); Ruiz, C. Carnero [Departamento de Física Aplicada II, Escuela de Ingenierías, Universidad de Málaga, Campus de Teatinos, 29071, Málaga (Spain); Galisteo-González, F. [Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Medina-O' Donnell, M.; Parra, A. [Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

2016-10-15

The fluorescence quenching of human serum albumin (HSA) by diphthaloylmaslinic acid (FMA) at different pH and temperature values was investigated by both steady-state and time-resolved fluorescence. The quenching was found to be appreciable, and an upward-curving Stern–Volmer trend was detected in all cases studied at high drug concentrations. This non-linear dependence reveals the presence of a not purely dynamic fluorescence-quenching mechanism. The experimental data were analyzed using the ground-state complex and sphere action quenching models. The latter model offers a good fit with the experimental results. Time-resolved studies corroborate the simultaneous presence of dynamic and sphere action quenching. The pH significantly affects the binging affinity of FMA to HSA, being stronger at pH 7.4 than at pH 3.0. Thermodynamic parameters ΔG°, ΔH°, and ΔS° were evaluated at different temperatures to examine the nature of the binding forces between FMA and HSA. At pH 7.4, electrostatic interactions controlled the association process, whereas at pH 3.0 the dominant forces seemed to be the hydrophobic interactions. The probable binding site of FMA on HSA was located at subdomain IIA, as suggested by displacement measurements. The surface electrical charge of FMA–HSA complexes was studied by measuring their electrophoretic mobility. Results corroborated the binding of the ligand to the protein. Circular dichroism experiments showed that the FMA binding does not alter the secondary structure of the protein. - Highlights: • The interaction between diphthaloylmaslinic acid and human serum albumin was studied at different temperature and pH values. • Fluorescence studies suggested the simultaneous quenching by dynamic and static mechanisms. • Electrostatic interactions dominate the association process at physiological pH. • Hydrophobic forces control the binding at pH 3.0. • Circular dichroism studies revealed that the secondary structure of HSA was

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

Chlorophyll fluorescence as a parameter for frost hardiness in winter wheat. A comparison with other hardiness parameters.

NARCIS (Netherlands)

Clement, JMAM; vanHasselt, PR

1996-01-01

Frost hardiness of winter wheat leaves (Triticum aestivum L. cv. Urban) was measured during an eight weeks hardening period using chlorophyll fluorescence. Determination of frost induced damage after freezing, measured as the decrease of photochemical capacity of photosystem II (F-V/F-M =

Silver Nanoparticle-Based Fluorescence-Quenching Lateral Flow Immunoassay for Sensitive Detection of Ochratoxin A in Grape Juice and Wine

Science.gov (United States)

Jiang, Hu; Li, Xiangmin; Xiong, Ying; Pei, Ke; Nie, Lijuan; Xiong, Yonghua

2017-01-01

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)32+-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. PMID:28264472

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.

Chlorophyll a and chlorophyllide a inside liposomes made of saturated and unsaturated lipids: A possible impact of the lipids microenvironment

Directory of Open Access Journals (Sweden)

Petrović Sanja M.

2014-01-01

Full Text Available The aim of this work was to examine a possible impact of liposomes lipids microenvironment, dictated by a chemical composition of the fatty acid branches, on incorporation and spectral behaviour of chlorophyll a, and its derivative, chlorophyllide a inside small liposomes. The liposomes with the incorporated chlorophylls were made of dimirystoyl phosphatidylcholine (DMPC, and unsaturated phosphatidylcholine (PC, containing significant fractions of unsaturated fatty acid moieties. In order to achieve the goal, both absorption and fluorescence polarization spectroscopy were applied, and the obtained data for the two incorporated pigments, which play a role of molecular sensors, were compared. In addition, quercetin, a well-known antioxidant, was used as the (chlorophylls emission quencher, in order to estimate the type of environment sensed by the two pigments for the two liposomes that differ in chemical composition. The results, based primarily on fluorescence polarization data have shown that the emissions as well as the emission quenching were notably affected by a change in the lipids’ chemical composition. That is an indirect proof of the impact of the liposomes microenvironment on the incorporated pigments’ spectral behaviour.[ Projekat Ministarstva nauke Republike Srbije, br. TR-34012 i br. OI-172044

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

Science.gov (United States)

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

2015-01-25

In this contribution, a luminescent gold nanoclusters which were synthesized by bovine serum albumin as novel fluorescent probes were successfully utilized for the determination of D-penicillamine for the first time. Cupric ion was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of D-penicillamine caused obvious restoration of fluorescence intensity of the Cu(2+)-gold nanoclusters system. Under optimum conditions, the increment in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by D-penicillamine was linearly proportional to the concentration of D-penicillamine in the range of 2.0×10(-5)-2.39×10(-4) M. The detection limit for D-penicillamine was 5.4×10(-6) M. With the off-on fluorescence signal at 650 nm approaching the near-infrared region, the present sensor for D-penicillamine detection had high sensitivity and low spectral interference. Furthermore, the novel gold nanoclusters-based fluorescent sensor has been applied to the determination of D-penicillamine in real biological samples with satisfactory results. Copyright © 2014 Elsevier B.V. All rights reserved.

Photophysical studies on the interaction of amides with Bovine Serum Albumin (BSA) in aqueous solution: Fluorescence quenching and protein unfolding

International Nuclear Information System (INIS)

Kumaran, R.; Ramamurthy, P.

2014-01-01

Addition. of amides containing a H-CO(NH 2 ) or CH 3 -CO(NH 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 3 ) 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 2 )), whereas a shift in the emission maximum only towards the red region results on the addition of acetamide (CH 3 -CONH 2 ). Steady state emission spectral studies reveal that amides that possess a free NH 2 and N(CH 3 ) 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 DMF 2 hydrogen and the carbonyl oxygen of amide form a concerted hydrogen-bonding network with the carbonyl oxygen and the amino moieties of amino acids respectively is established from fluorescence methods. -- Highlights: • The manuscript deals with the absorption, emission and fluorescence lifetime studies of Bovine Serum Albumin with amides in aqueous medium. • Fluorescence is correlated to the presence of fluorescing amino acid, tryptophan located in a heterogeneous environment. • This article provides an insight about the fluorescence spectral characteristics of a protein

Oxygen optical gas sensing by reversible fluorescence quenching in photo-oxidized poly(9,9-dioctylfluorene) thin films.

Science.gov (United States)

Anni, M; Rella, R

2010-02-04

We investigated the fluorescence (FL) dependence on the environment oxygen content of poly(9,9-dioctylfluorene) (PF8) thin films. We show that the PF8 interactions with oxygen are not limited to the known irreversible photo-oxidation, resulting in the formation of Keto defects, but also reversible FL quenching is observed. This effect, which is stronger for the Keto defects than for the PF8, has been exploited for the realization of a prototype oxygen sensor based on FL quenching. The sensing sensitivity of Keto defects is comparable with the state of the art organic oxygen sensors based on phosphorescence quenching.

New evidence for primordial action site of Fluazifop-P-butyl on Acanthospermum hispidum seedlings: From the effects on chlorophyll fluorescence characteristics and histological observation.

Science.gov (United States)

Shang, Yuhong; Yang, Congjun; Liu, Zhihang; Song, Jiqing; Li, Pingliang; Li, Lingxu; Zhou, Fei; Xin, Hua; Wan, Fanghao; Matsumoto, Hiroshi; Luo, Xiaoyong

2017-10-01

Acanthospermum hispidum DC, an Asteraceae weed species, was very susceptible to fluazifop-P-butyl, but tolerant to other aryloxyphenoxypropionate herbicides, such as haloxyfop-P-methyl. However, other Asteraceae weeds including Bidens pilosa were all tolerant to fluazifop-P-butyl. Membrane lipid peroxidation by increasing the levels of reactive oxygen species (ROS) was proposed as an action mechanism of fluazifop-P-butyl in A. hispidum. To further clarify the primordial action site of fluazifop-P-butyl in this species, the effects on chlorophyll fluorescence characteristics and cytohistology of apical meristems were studied. Chlorophyll fluorescence characteristics (CFC) in sensitive A. hispidum seedlings were markedly affected by 10μM fluazifop-P-butyl, with the dark fluorescence yield (Fo), maximal fluorescence yield (Fm), maximal PS II quantum yield (Fv/Fm), effective photosystem II (PS II) quantum yield [Y(II)], and quantum yield of regulated energy dissipation [Y(NPQ)] declining, quantum yield of nonregulated energy dissipation [Y(NO)] rising, but these measures were not affected in Bidens pilosa. The effects of fluazifop-P-butyl on chlorophyll fluorescence properties were observed on the growing point before the mature leaves by about 4-6h. Haloxyfop-P-methyl, a control herbicide, had no effects on CFC of either A. hispidum or B. pilosa. In addition, damage to apical meristem cells of A. hispidum was observed at 6 HAT prior to changes in chlorophyll fluorescence parameters suggesting that the primary action site of fluazifop-P-butyl in this species is in the apical meristem and the effects on CFC may be the results of secondary action. Copyright © 2017 Elsevier Inc. All rights reserved.

Quenched carbonaceous composite - Fluorescence spectrum compared to the extended red emission observed in reflection nebulae

Science.gov (United States)

Sakata, Akira; Wada, Setsuko; Narisawa, Takatoshi; Asano, Yoichi; Iijima, Yutaka; Onaka, Takashi; Tokunaga, Alan T.

1992-01-01

The photoluminescence (fluorescence) of a film of the laboratory-synthesized quenched carbonaceous composite (filmy QCC) is shown to have a single broad emission feature with a peak wavelength that varies from 670 to 725 nm, and coincides with that of the extended red emission observed in reflection nebulae. The rapid decay of the filmy QCC red fluorescence in air and of the stable blue fluorescence of the filmy QCC dissolved in liquid Freon suggests that the red fluorescence originates from the interaction of active chemical species and aromatic components in the filmy QCC. A material similar in nature to that of the filmy QCC may be a major component of interstellar dust.

Remote sensing of chlorophyll a fluorescence of vegetation canopies. 1. Near and far field measurement techniques

International Nuclear Information System (INIS)

Cecchi, G.; Mazzinghi, P.; Pantani, L.; Valentini, R.; Tirelli, D.; De Angelis, P.

1994-01-01

This article presents instruments and techniques, used in several vegetation monitoring experiments. Simultaneous monitoring was performed with different approaches, including fluorescence lidar and passive remote sensing, leaf level reflectance, and laser fluorimetry, and compared with physiological measurements. Most of the instrumentation described was designed and built for this application. Experiments were carried out in the laboratory and in the field, to investigate the relationship between chlorophyll fluorescence spectra and plant ecophysiology. Remote sensing, spectroscopy, and ecophysiology data were then collected by an intensive research team, joining different experiences and working in national and international projects

High-throughput screening assay of hepatitis C virus helicase inhibitors using fluorescence-quenching phenomenon

International Nuclear Information System (INIS)

Tani, Hidenori; Akimitsu, Nobuyoshi; Fujita, Osamu; Matsuda, Yasuyoshi; Miyata, Ryo; Tsuneda, Satoshi; Igarashi, Masayuki; Sekiguchi, Yuji; Noda, Naohiro

2009-01-01

We have developed a novel high-throughput screening assay of hepatitis C virus (HCV) nonstructural protein 3 (NS3) helicase inhibitors using the fluorescence-quenching phenomenon via photoinduced electron transfer between fluorescent dyes and guanine bases. We prepared double-stranded DNA (dsDNA) with a 5'-fluorescent-dye (BODIPY FL)-labeled strand hybridized with a complementary strand, the 3'-end of which has guanine bases. When dsDNA is unwound by helicase, the dye emits fluorescence owing to its release from the guanine bases. Our results demonstrate that this assay is suitable for quantitative assay of HCV NS3 helicase activity and useful for high-throughput screening for inhibitors. Furthermore, we applied this assay to the screening for NS3 helicase inhibitors from cell extracts of microorganisms, and found several cell extracts containing potential inhibitors.

Determination of catecholamine in human serum by a fluorescent quenching method based on a water-soluble fluorescent conjugated polymer-enzyme hybrid system.

Science.gov (United States)

Huang, Hui; Gao, Yuan; Shi, Fanping; Wang, Guannan; Shah, Syed Mazhar; Su, Xingguang

2012-03-21

In this paper, a sensitive water-soluble fluorescent conjugated polymer biosensor for catecholamine (dopamine DA, adrenaline AD and norepinephrine NE) was developed. In the presence of horse radish peroxidase (HRP) and H(2)O(2), catecholamine could be oxidized and the oxidation product of catecholamine could quench the photoluminescence (PL) intensity of poly(2,5-bis(3-sulfonatopropoxy)-1,4-phenylethynylenealt-1,4-poly(phenylene ethynylene)) (PPESO(3)). The quenching PL intensity of PPESO(3) (I(0)/I) was proportional to the concentration of DA, AD and NE in the concentration ranges of 5.0 × 10(-7) to 1.4 × 10(-4), 5.0 × 10(-6) to 5.0 × 10(-4), and 5.0 × 10(-6) to 5.0 × 10(-4) mol L(-1), respectively. The detection limit for DA, AD and NE was 1.4 × 10(-7) mol L(-1), 1.0 × 10(-6) and 1.0 × 10(-6) mol L(-1), respectively. The PPESO(3)-enzyme hybrid system based on the fluorescence quenching method was successfully applied for the determination of catecholamine in human serum samples with good accuracy and satisfactory recovery. The results were in good agreement with those provided by the HPLC-MS method.

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

International Nuclear Information System (INIS)

Liu, Qi; Huang, Aizhen; Wang, Nan; Zheng, Guan; Zhu, Lihua

2015-01-01

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 −1 , with a limit of detection of 0.3 μmol L −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 −1 and a detection limit of 0.3 μmol L −1

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...

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; Warren, Frederick J; Gidley, Michael J

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. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

A Label-Free Microfluidic Biosensor for Activity Detection of Single Microalgae Cells Based on Chlorophyll Fluorescence

Science.gov (United States)

Wang, Junsheng; Sun, Jinyang; Song, Yongxin; Xu, Yongyi; Pan, Xinxiang; Sun, Yeqing; Li, Dongqing

2013-01-01

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. PMID:24287532

Chlorophyll fluorescence is a rigorous, high throughput tool to analyze the impacts of genotype, species, and stress on plant and ecosystem productivity

Science.gov (United States)

Ewers, B. E.; Pleban, J. R.; Aston, T.; Beverly, D.; Speckman, H. N.; Hosseini, A.; Bretfeld, M.; Edwards, C.; Yarkhunova, Y.; Weinig, C.; Mackay, D. S.

2017-12-01

Abiotic and biotic stresses reduce plant productivity, yet high-throughput characterization of plant responses across genotypes, species and stress conditions are limited by both instrumentation and data analysis techniques. Recent developments in chlorophyll a fluorescence measurement at leaf to landscape scales could improve our predictive understanding of plants response to stressors. We analyzed the interaction of species and stress across two crop types, five gymnosperm and two angiosperm tree species from boreal and montane forests, grasses, forbs and shrubs from sagebrush steppe, and 30 tree species from seasonally wet tropical forest. We also analyzed chlorophyll fluorescence and gas exchange data from twelve Brassica rapa crop accessions and 120 recombinant inbred lines to investigate phenotypic responses to drought. These data represent more than 10,000 measurements of fluorescence and allow us to answer two questions 1) are the measurements from high-throughput, hand held and drone-mounted instruments quantitatively similar to lower throughput camera and gas exchange mounted instruments and 2) do the measurements find differences in genotypic, species and environmental stress on plants? We found through regression that the high and low throughput instruments agreed across both individual chlorophyll fluorescence components and calculated ratios and were not different from a 1:1 relationship with correlation greater than 0.9. We used hierarchical Bayesian modeling to test the second question. We found a linear relationship between the fluorescence-derived quantum yield of PSII and the quantum yield of CO2 assimilation from gas-exchange, with a slope of ca. 0.1 indicating that the efficiency of the entire photosynthetic process was about 10% of PSII across genotypes, species and drought stress. Posterior estimates of quantum yield revealed that drought-treatment, genotype and species differences were preserved when accounting for measurement uncertainty

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.

THE USE OF CHLOROPHYLL FLUORESCENCE «a» FOR BIOTESTING OF THE AQUATIC ENVIRONMENT

Directory of Open Access Journals (Sweden)

V. A. Osipov

2012-01-01

Full Text Available The impact on marine algae Thalassiosiraweisflogii, Pseudo-nitzshiadelicatissima of copper sulfate, chloride of mercury, methylmercury were studied. Found a sharp increase sensitivity FS 2 of microalgae cultures and natural phytoplankton to salts of heavy metals in the conditions of the light of the stress that is associated with inhibition of protein synthetic reactions. Conclusions are made about the prospects of the use of fluorescence of chlorophyll "a" for biotesting.

Characterization of the alterations of the chlorophyll a fluorescence induction curve after addition of Photosystem II inhibiting herbicides

NARCIS (Netherlands)

Hiraki, M.; Rensen, van J.J.S.; Vredenberg, W.J.; Wakabayashi, K.

2003-01-01

The effects of Photosystem II inhibiting herbicides, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron), atrazine and two novel 2-benzylamino-1,3,5-triazine compounds, on photosynthetic oxygen evolution and chlorophyll a fluorescence induction were measured in thylakoids isolated from Chenopodium

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.

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

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...

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}.

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...... parameter, maximum quantum yield efficiency of PSII (Fv/Fm) is used as a physiological marker for early stress detection in PSII in plants. We established a reproducible protocol to measure response of wheat genotypes to high temperature based on Fv/Fm. The heat treatment of 40°C in 300 µmol m-2s-1 PAR...... enabled the identification of contrasting wheat genotypes that can be used to study the genetic and physiological nature of heat stress tolerance to dissect quantitative traits into simpler and more heritable traits....

Validation of photosynthetic-fluorescence parameters as biomarkers for isoproturon toxic effect on alga Scenedesmus obliquus.

Science.gov (United States)

Dewez, David; Didur, Olivier; Vincent-Héroux, Jonathan; Popovic, Radovan

2008-01-01

Photosynthetic-fluorescence parameters were investigated to be used as valid biomarkers of toxicity when alga Scenedesmus obliquus was exposed to isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] effect. Chlorophyll fluorescence induction of algal cells treated with isoproturon showed inactivation of photosystem II (PSII) reaction centers and strong inhibition of PSII electron transport. A linear correlation was found (R2>or=0.861) between the change of cells density affected by isoproturon and the change of effective PSII quantum yield (PhiM'), photochemical quenching (qP) and relative photochemical quenching (qP(rel)) values. The cells density was also linearly dependent (R2=0.838) on the relative unquenched fluorescence parameter (UQF(rel)). Non-linear correlation was found (R2=0.937) only between cells density and the energy transfer efficiency from absorbed light to PSII reaction center (ABS/RC). The order of sensitivity determined by the EC-50% was: UQF(rel)>PhiM'>qP>qP(rel)>ABS/RC. Correlations between cells density and those photosynthetic-fluorescence parameters provide supporting evidence to use them as biomarkers of toxicity for environmental pollutants.

Concentration quenching in Nd-doped glasses

International Nuclear Information System (INIS)

Stokowski, S.E.; Cook, L.; Mueller, H.; Weber, M.J.

1984-01-01

Fluorescence from trivalent Nd in solids is unfortunately quenched by interactions between Nd ions. Thus, laser materials with high Nd concentrations have reduced efficiencies because of this self-quenching, also known as concentration quenching. Nd self-quenching in different crystals and glasses varies considerably. We are therefore investigating this effect in a large number of materials in an effort to: (1) find those materials with long Nd fluorescent lifetimes at high Nd concentrations; and (2) elucidate the basic mechanisms of quenching and how the material structure controls its magnitude. We have concentrated on Nd-doped glasses because they provide a rich variety of structures, albeit complicated by Nd site inhomogeneities, and are easily and quickly made

High resolution measurements of solar induced chlorophyll fluorescence in the Fraunhofer oxigen bands

Science.gov (United States)

Mazzoni, M.; Agati, G.; Cecchi, G.; Toci, G.; Mazzinghi, P.

2017-11-01

Spectra of solar radiance reflected by leaves close to the Fraunhofer bands show the net contribution of chlorophyll fluorescence emission which adds to the reflected solar spectra. In a laboratory experiment, a low stray light, high resolution, 0.85 m double monochromator was used to filter radiation living leaves still attached to the plant in correspondence of the 687 nm and 760 nm O2 absorption bands. Reference spectra from a non fluorescent white reference were also acquired. Acquisition was performed by a Microchannel plate (MCP) intensified diode array with 512 elements. A fit of the spectral data outside the absorption lines allowed to retrieve the spectral base-line as a function of wavelength for the reference panel and the leaf. Reflectance functions were determined extending the Plascyck equation system to all the resolved lines of the oxygen absorption bands and using the base-lines for the continuum values. Fluorescence was deduced from the same equation system, using both the measured leaf and reference radiance spectra and the leaf reflectance fitting function.

"Super-quenching" state protects Symbiodinium from thermal stress - Implications for coral bleaching.

Science.gov (United States)

Slavov, Chavdar; Schrameyer, Verena; Reus, Michael; Ralph, Peter J; Hill, Ross; Büchel, Claudia; Larkum, Anthony W D; Holzwarth, Alfred R

2016-06-01

The global rise in sea surface temperatures causes regular exposure of corals to high temperature and high light stress, leading to worldwide disastrous coral bleaching events (loss of symbiotic dinoflagellates (Symbiodinium) from reef-building corals). Our picosecond chlorophyll fluorescence experiments on cultured Symbiodinium clade C cells exposed to coral bleaching conditions uncovered the transformations of the alga's photosynthetic apparatus (PSA) that activate an extremely efficient non-photochemical "super-quenching" mechanism. The mechanism is associated with a transition from an initially heterogeneous photosystem II (PSII) pool to a homogeneous "spillover" pool, where nearly all excitation energy is transferred to photosystem I (PSI). There, the inherently higher stability of PSI and high quenching efficiency of P(700)(+) allow dumping of PSII excess excitation energy into heat, resulting in almost complete cessation of photosynthetic electron transport (PET). This potentially reversible "super-quenching" mechanism protects the PSA against destruction at the cost of a loss of photosynthetic activity. We suggest that the inhibition of PET and the consequent inhibition of organic carbon production (e.g. sugars) in the symbiotic Symbiodinium provide a trigger for the symbiont expulsion, i.e. bleaching. Copyright © 2016. Published by Elsevier B.V.

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.

Detection of trace tetracycline in fish via synchronous fluorescence quenching with carbon quantum dots coated with molecularly imprinted silica

Science.gov (United States)

Yang, Ji; Lin, Zheng-Zhong; Nur, A.-Zha; Lu, Yan; Wu, Ming-Hui; Zeng, Jun; Chen, Xiao-Mei; Huang, Zhi-Yong

2018-02-01

A novel fluorescence-based sensor combining synchronous fluorescence spectroscopy (SFS) with molecularly imprinted polymers (MIPs) was fabricated with reverse microemulsion method. Tetracycline (TC), (3-aminopropyl) triethoxysilane (APTES), tetraethyl orthosilicate (TEOS) and carbon quantum dots (CDs) were used as template, functional monomer, cross-linker and signal sources respectively in the probe preparation. A synchronous fluorescence emission (λem) at 355 nm was observed for the prepared MIP-coated CDs (MIP@CDs) particles when the wavelength interval (Δλ) was set as 70 nm, and the synchronous fluorescence intensity could be rapidly and efficiently quenched by TC based on inner filter effect (IFE). The quenching efficiencies of synchronous fluorescence intensity was linearly fitted with tetracycline (TC) concentrations ranging from 0.1 to 50 μmol L- 1 with a detection limit (DL) of 9 nmol L- 1 (3σ, n = 9). The MIP@CDs was used as a probe to detect TC in fish samples with the recoveries ranging from 98.4% to 103.1% and the relative standard deviation less than 6.0%. The results illustrated that the as-prepared MIP@CDs could be applied to the detection of trace TC in fish samples with rapidity, high sensitivity and accuracy.

Heterologous Expression of Moss Light-harvesting Complex Stress-related 1 (LHCSR1), the Chlorophyll a-Xanthophyll Pigment-protein Complex Catalyzing Non-photochemical Quenching, in Nicotiana sp.*

Science.gov (United States)

Pinnola, Alberta; Ghin, Leonardo; Gecchele, Elisa; Merlin, Matilde; Alboresi, Alessandro; Avesani, Linda; Pezzotti, Mario; Capaldi, Stefano; Cazzaniga, Stefano; Bassi, Roberto

2015-01-01

Oxygenic photosynthetic organisms evolved mechanisms for thermal dissipation of energy absorbed in excess to prevent formation of reactive oxygen species. The major and fastest component, called non-photochemical quenching, occurs within the photosystem II antenna system by the action of two essential light-harvesting complex (LHC)-like proteins, photosystem II subunit S (PSBS) in plants and light-harvesting complex stress-related (LHCSR) in green algae and diatoms. In the evolutionary intermediate Physcomitrella patens, a moss, both gene products are active. These proteins, which are present in low amounts, are difficult to purify, preventing structural and functional analysis. Here, we report on the overexpression of the LHCSR1 protein from P. patens in the heterologous systems Nicotiana benthamiana and Nicotiana tabacum using transient and stable nuclear transformation. We show that the protein accumulated in both heterologous systems is in its mature form, localizes in the chloroplast thylakoid membranes, and is correctly folded with chlorophyll a and xanthophylls but without chlorophyll b, an essential chromophore for plants and algal LHC proteins. Finally, we show that recombinant LHCSR1 is active in quenching in vivo, implying that the recombinant protein obtained is a good material for future structural and functional studies. PMID:26260788

Flexibility of cold- and heat-adapted subtilisin-like serine proteinases evaluated with fluorescence quenching and molecular dynamics

DEFF Research Database (Denmark)

Sigtryggsdóttir, Asta Rós; Papaleo, Elena; Thorbjarnardóttir, Sigríður H.

2014-01-01

activity of cold adapted enzymes when compared to homologues from thermophiles, reflects their higher molecular flexibility. To assess a potential difference in molecular flexibility between the two homologous proteinases, we have measured their Trp fluorescence quenching by acrylamide at different......The subtilisin-like serine proteinases, VPR, from a psychrotrophic Vibrio species and aqualysin I (AQUI) from the thermophile Thermus aquaticus, are structural homologues, but differ significantly with respect to stability and catalytic properties. It has been postulated that the higher catalytic...... to Trp (Y191W). A lower quenching effect of acrylamide on the intrinsic fluorescence of the thermophilic AQUI_Y191W was observed at all temperatures measured (10-55°C), suggesting that it possesses a more rigid structure than VPR. The MD analysis (Cα rmsf profiles) showed that even though VPR and AQUI...

Predictability and environmental drivers of chlorophyll fluctuations vary across different time scales and regions of the North Sea

Science.gov (United States)

Blauw, Anouk N.; Benincà, Elisa; Laane, Remi W. P. M.; Greenwood, Naomi; Huisman, Jef

2018-02-01

Phytoplankton concentrations display strong temporal variability at different time scales. Recent advances in automated moorings enable detailed investigation of this variability. In this study, we analyzed phytoplankton fluctuations at four automated mooring stations in the North Sea, which measured phytoplankton abundance (chlorophyll) and several environmental variables at a temporal resolution of 12-30 min for two to nine years. The stations differed in tidal range, water depth and freshwater influence. This allowed comparison of the predictability and environmental drivers of phytoplankton variability across different time scales and geographical regions. We analyzed the time series using wavelet analysis, cross correlations and generalized additive models to quantify the response of chlorophyll fluorescence to various environmental variables (tidal and meteorological variables, salinity, suspended particulate matter, nitrate and sea surface temperature). Hour-to-hour and day-to-day fluctuations in chlorophyll fluorescence were substantial, and mainly driven by sinking and vertical mixing of phytoplankton cells, horizontal transport of different water masses, and non-photochemical quenching of the fluorescence signal. At the macro-tidal stations, these short-term phytoplankton fluctuations were strongly driven by the tides. Along the Dutch coast, variation in salinity associated with the freshwater influence of the river Rhine played an important role, while in the central North Sea variation in weather conditions was a major determinant of phytoplankton variability. At time scales of weeks to months, solar irradiance, nutrient conditions and thermal stratification were the dominant drivers of changes in chlorophyll concentrations. These results show that the dominant drivers of phytoplankton fluctuations differ across marine environments and time scales. Moreover, our findings show that phytoplankton variability on hourly to daily time scales should not be

Hyperspectral solar-induced chlorophyll fluorescence of urban tree leaves: Analyses and applications

Science.gov (United States)

Van Wittenberghe, Shari

Solar energy is the primary energy source for life on Earth which is converted into chemical energy through photosynthesis by plants, algae and cyanobacteria, releasing fuel for the organisms' activities. To dissipate excess of absorbed light energy, plants emit chlorophyll (Chl) fluorescence (650-850 nm) from the same location where photosynthesis takes place. Hence, it provides information on the efficiency of primary energy conversion. From this knowledge, many applications on vegetation and crop stress monitoring could be developed, a necessity for our planet under threat of a changing global climate. Even though the Chl fluorescence signal is weak against the intense reflected radiation background, methods for retrieving the solar-induced Chl fluorescence have been refined over the last years, both at leaf and airborne scale. However, a lack of studies on solar-induced Chl fluorescence gives difficulties for the interpretation of the signal. Within this thesis, hyperspectral upward and downward solar-induced Chl fluorescence is measured at leaf level. Fluorescence yield (FY) is calculated as well as different ratios characterizing the emitted Chl fluorescence shape. The research in this PhD dissertation illustrates the influence of several factors on the solar-induced Chl fluorescence signal. For instance, both the intensity of FY and its spectral shape of urban tree leaves are able to change under influence of stress factors such as traffic air pollution. This shows how solar-induced Chl fluorescence could function as an early stress indicator for vegetation. Further, it is shown that the signal contains information on the ultrastructure of the photosynthetic apparatus. Also, it is proven that the leaf anatomical structure and related light scattering properties play a role in the partitioning between upward and downward Chl fluorescence emission. All these findings indicate how the Chl fluorescence spectrum is influenced by factors which also influence

Prooxidative and antioxidative properties of β-carotene in chlorophyll and riboflavin photosensitized oil-in-water emulsions.

Science.gov (United States)

Park, JungWoo; Kim, Tae Soo; Kim, Mi-Ja; Lee, JaeHwan

2013-09-01

Effects of β-carotene on the oxidative stability of chlorophyll or riboflavin photosensitized oil-in-water (O/W) emulsions were determined by analysing the depleted headspace oxygen content, lipid hydroperoxides, fluorescence intensity, and headspace volatiles. As the concentration of β-carotene increased from 0 to 10, 100, and 1000 μM, the oxidative stability of samples containing chlorophylls decreased in a concentration-dependent manner under light, indicating that β-carotene acted as a prooxidant. However, in riboflavin photosensitized O/W emulsions, 100 and 1000 μM β-carotene inhibited lipid oxidation. Although β-carotene protected both photosensitisers in O/W emulsions, β-carotene displayed antioxidative or prooxidative properties, which depended on the polarity of the photosensitisers. The development of t-2-heptenal and 1-octen-3-ol increased greatly in chlorophyll sensitised O/W emulsions with an increase in β-carotene concentration, implying that more singlet oxygen oxidation occurred due to the higher levels of remaining chlorophylls. However, the content of t-2-heptenal and 1-octen-3-ol in the riboflavin sensitised O/W emulsions was not significantly correlated with the β-carotene concentration, which indicates that β-carotene in the lipid particles effectively quenched singlet oxygen. Copyright © 2013 Elsevier Ltd. All rights reserved.

Validation of photosynthetic-fluorescence parameters as biomarkers for isoproturon toxic effect on alga Scenedesmus obliquus

International Nuclear Information System (INIS)

Dewez, David; Didur, Olivier; Vincent-Heroux, Jonathan; Popovic, Radovan

2008-01-01

Photosynthetic-fluorescence parameters were investigated to be used as valid biomarkers of toxicity when alga Scenedesmus obliquus was exposed to isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] effect. Chlorophyll fluorescence induction of algal cells treated with isoproturon showed inactivation of photosystem II (PSII) reaction centers and strong inhibition of PSII electron transport. A linear correlation was found (R 2 ≥ 0.861) between the change of cells density affected by isoproturon and the change of effective PSII quantum yield (Φ M' ), photochemical quenching (q P ) and relative photochemical quenching (q P(rel) ) values. The cells density was also linearly dependent (R 2 = 0.838) on the relative unquenched fluorescence parameter (UQF (rel) ). Non-linear correlation was found (R 2 = 0.937) only between cells density and the energy transfer efficiency from absorbed light to PSII reaction center (ABS/RC). The order of sensitivity determined by the EC-50% was: UQF (rel) > Φ M' > q P > q P(rel) > ABS/RC. Correlations between cells density and those photosynthetic-fluorescence parameters provide supporting evidence to use them as biomarkers of toxicity for environmental pollutants. - Photosynthetic-fluorescence parameters are reliable biomarkers of isoproturon toxicity

Oxygen transmittance correction for solar-induced chlorophyll fluorescence measured on proximal sensing: application to the NASA-GSFC fusion tower

Science.gov (United States)

Since oxygen (O2) absorption of light becomes more pronounced at higher pressure levels, even a few meters distance between the target and the sensor can strongly affect canopy leaving Solar-Induced chlorophyll Fluorescence (SIF) retrievals. This study was conducted to quantify the consequent error ...

Thermotolerance of apple tree leaves probed by chlorophyll a fluorescence and modulated 820 nm reflection during seasonal shift.

Science.gov (United States)

Duan, Ying; Zhang, Mengxia; Gao, Jin; Li, Pengmin; Goltsev, Vasilij; Ma, Fengwang

2015-11-01

During the seasonal shift from June to August, air temperatures increase. To explore how apple trees improve their thermotolerance during this shift, we examined the photochemical reaction capacity of apple tree leaves by simultaneous measurement of prompt chlorophyll fluorescence, delayed chlorophyll fluorescence, and modulated 820 nm reflection at varying temperatures. It was found that the reaction centers and antennae of photosystem II (PSII) and photosystem I (PSI), the donor side of PSII, the electron transfer capacity from QA to QB, and the reoxidation capacity of plastoquinol were all sensitive to heat stress, particularly in June. As the season shifted, apple tree leaves improved in thermotolerance. Interestingly, the acclimation to seasonal shift enhanced the thermotolerance of PSII and PSI reaction centers more than that of their antennae, and the activity of PSII more than that of PSI. This may be a strategy for plant adaptation to changes in environmental temperatures. In addition, results from prompt and delayed fluorescence, as well as modulated 820 nm reflection corroborate each other. We suggest that the simultaneous measurement of the three independent signals may provide more information on thermal acclimation mechanisms of photochemical reactions in plant leaves. Copyright © 2015 Elsevier B.V. All rights reserved.

Enhancement of fluorescence quenching and exciplex formation in DNA major groove by double incorporation of modified fluorescent deoxyuridines.

Science.gov (United States)

Tanaka, Makiko; Oguma, Kazuhiro; Saito, Yoshio; Saito, Isao

2012-06-15

5-(1-Naphthalenylethynyl)-2'-deoxyuridine ((N)U) and 5-[(4-cyano-1-naphthalenyl)ethynyl]-2'-deoxyuridine ((CN)U) were synthesized and incorporated into oligodeoxynucleotides. Fluorescence emissions of modified duplexes containing double (N)U were efficiently quenched depending upon the sequence pattern of the naphthalenes in DNA major groove, as compared to the duplex possessing single (N)U. When one of the naphthalene moieties has a cyano substituent, the exciplex emission from the chromophores in DNA major groove was observed at longer wavelength. Copyright © 2012 Elsevier Ltd. All rights reserved.

Generation of fluorescence quenchers from the triplet states of chlorophylls in the major light-harvesting complex II from green plants

NARCIS (Netherlands)

Barzda, V.; Vengris, M.; Valkunas, L.; van Amerongen, H.; van Grondelle, R.

2000-01-01

Laser flash-induced changes of the fluorescence yield were studied in aggregates of light-harvesting complex II (LHCII) on a time scale ranging from microseconds to seconds. Carotenoid (Car) and chlorophyll (Chl) triplet states, decaying with lifetimes of several microseconds and hundreds of

Label-Free Platform for MicroRNA Detection Based on the Fluorescence Quenching of Positively Charged Gold Nanoparticles to Silver Nanoclusters.

Science.gov (United States)

Miao, Xiangmin; Cheng, Zhiyuan; Ma, Haiyan; Li, Zongbing; Xue, Ning; Wang, Po

2018-01-16

A novel strategy was developed for microRNA-155 (miRNA-155) detection based on the fluorescence quenching of positively charged gold nanoparticles [(+)AuNPs] to Ag nanoclusters (AgNCs). In the designed system, DNA-stabilized Ag nanoclusters (DNA/AgNCs) were introduced as fluorescent probes, and DNA-RNA heteroduplexes were formed upon the addition of target miRNA-155. Meanwhile, the (+)AuNPs could be electrostatically adsorbed on the negatively charged single-stranded DNA (ssDNA) or DNA-RNA heteroduplexes to quench the fluorescence signal. In the presence of duplex-specific nuclease (DSN), DNA-RNA heteroduplexes became a substrate for the enzymatic hydrolysis of the DNA strand to yield a fluorescence signal due to the diffusion of AgNCs away from (+)AuNPs. Under the optimal conditions, (+)AuNPs displayed very high quenching efficiency to AgNCs, which paved the way for ultrasensitive detection with a low detection limit of 33.4 fM. In particular, the present strategy demonstrated excellent specificity and selectivity toward the detection of target miRNA against control miRNAs, including mutated miRNA-155, miRNA-21, miRNA-141, let-7a, and miRNA-182. Moreover, the practical application value of the system was confirmed by the evaluation of the expression levels of miRNA-155 in clinical serum samples with satisfactory results, suggesting that the proposed sensing platform is promising for applications in disease diagnosis as well as the fundamental research of biochemistry.

Afterglow of chlorophyll in vivo and photosynthesis

NARCIS (Netherlands)

Goedheer, J.C.

1962-01-01

Two pigment systems are involved in the afterglow of chlorophyll a-containing cells. Absorption in only one of these systems (promoting or “p” system) is effective in producing luminescence. If light is absorbed simultaneously by the other (quenching or “q” system), a decrease in luminescence

Fluorescência e teores de clorofilas em abacaxizeiro cv. pérola submetido a diferentes concentrações de sulfato de amônio Fluorescence and levels of chlorophyll in pineapple plants cv. perola submitted to different concentration of ammonium sulphate

Directory of Open Access Journals (Sweden)

Darlene Ana de Paula Vieira

2010-06-01

Full Text Available O presente trabalho teve como objetivo a análise da emissão da fluorescência da clorofila a e dos teores de clorofilas em plantas de Ananas comosus (L. Merril cv pérola, cultivadas em casa de vegetação, submetidas a quatro concentrações de nitrogênio por adição ou não de sulfato de amônio, de acordo com os seguintes tratamentos: Tº= 0 T1/2 = 15; T1 = 30; e T2 = 60 mg/kg solo. As determinações de fluorescência mínima (F0, máxima (Fm, variável (Fv, terminal (Ft e da eficiência fotoquímica máxima (Fv/Fm de folhas adaptadas ao escuro foram realizadas ao longo do dia, aos cinco dias após a segunda aplicação de sulfato de amônio, efetuada 120 dias após o transplantio. A adição de sulfato de amônio afetou a fluorescência variável e a máxima, mas não afetou a fluorescência mínima, a terminal nem a eficiência fotoquímica. Houve diferenças significativas entre os valores das variáveis da fluorescência ao longo do dia em que foram feitas as leituras. Houve diferenças nos teores de clorofilas foliares, em função das concentrações de sulfato de amônio aplicadas, com aumento para clorofila a e para a relação clorofila a/b, mas não para clorofila b.The present research aimed to analyze chlorophyll a fluorescence emission as well as chlorophyll levels in Ananas comosus (L. Merril cv Pérola grown under greenhouse conditions and submitted to four concentration of nitrogen, through addition or not of ammonium sulphate according to the following treatments: Tº= 0.000; T1/2 = 0.015; T1 =0.030; and T2 = 0.060 g/kg soil. Determinations of minimum (F0, maximum (Fm, variable (Fv, and terminal (Ft fluorescence and maximum photochemical efficiency (Fv/Fm of dark-adapted leaves were carried out during the day, five days after the second application of ammonium sulphate, carried out 120 days after the transplant. The results showed that the addition of ammonium sulphate affected variable and maximum fluorescence, but not

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

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

Science.gov (United States)

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

2014-02-26

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

Imaging of fast chlorophyll fluorescence induction curve (OJIP) parameters, applied in a screening study with wild barley (Hordeum spontaneum) genotypes under heat stress.

Science.gov (United States)

Jedmowski, Christoph; Brüggemann, Wolfgang

2015-10-01

We quantified the influence of heat stress (HS) on PSII by imaging of parameters of the fast chlorophyll fluorescence (CF) induction (OJIP) kinetic of 20 genotypes of wild barley (Hordeum spontaneum) covering a broad geographical spectrum. We developed a standardised screening procedure, allowing a repetitive fluorescence measurement of leaf segments. The impact of HS was quantified by calculating a Heat Resistance Index (HRI), derived from the decrease of the Performance Index (PI) caused by HS treatment and following recovery. For the genotype showing the lowest HRI, reduced maximum quantum yield (φP0) and increased relative variable fluorescence of the O-J phase (K-Peak) were detected after HS, whereas the basal fluorescence (F0) remained stable. An additional feature was a lowered fraction of active (QA-reducing) reaction centres (RCs). The disturbances disappeared after one day of recovery. Spatial heterogeneities of fluorescence parameters were detected, as the negative effect of HS was stronger in the leaf areas close to the leaf tip. The results of this study prove that chlorophyll fluorescence imaging (CFI) is suitable for the detection of HS symptoms and that imaging of JIP-Test parameters should be considered in future screening and phenotyping studies aiming for the characterisation of plant genotypes. Copyright © 2015 Elsevier B.V. All rights reserved.

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.

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.

Estimation of the effect of radionuclide contamination on Vicia sativa L. induction of chlorophyll fluorescence parameters using "Floratest" optical biosensor

Science.gov (United States)

Ruban, Yu.; Illienko, V.; Nesterova, N.; Pareniuk, O.; Shavanova, K.

2017-12-01

The presented research was aimed to determine the parameters of chlorophyll fluorescence (IChH) curve induction for Vicia sativa L. that were grown on radionuclide contaminated soils by using "Floratest" fluorometer. Plants were inoculated with 5 species of bacteria that might potentially block radionuclide uptake (Agrobacterium radiobacter IMBB-7246, Azotobacter chroococcum UKMB-6082, A. chroococcum UKMB-6003, Bacillus megaterium UKMB-5724, Rhizobium leguminosarum bv. viceae) and grown in sod-podzolic, chernozem and peat-bog soils, contaminated with 137Cs (4000±340 Bq/kg). As a result of research, it was determined that the most stressful factors for vetch plants are combination of soil radionuclide and presence of Bacillus megaterium UKM B-5724, as the number of inactive chlorophyll increased. In addition, the vetch plants significantly increased fixed level of fluorescence (Fst) under the influence of radioactive contamination in presence of Bacillus megaterium UKM B-5724, indicating inhibition of photosynthetic reactions. Other bacteria showed radioprotective properties in almost all types of soil.

Validation of photosynthetic-fluorescence parameters as biomarkers for isoproturon toxic effect on alga Scenedesmus obliquus

Energy Technology Data Exchange (ETDEWEB)

Dewez, David; Didur, Olivier; Vincent-Heroux, Jonathan [University of Quebec in Montreal, Department of Chemistry, Environmental Toxicology Research Center - TOXEN, 2101, Jeanne-Mance, Montreal, Quebec H2X 2J6 (Canada); Popovic, Radovan [University of Quebec in Montreal, Department of Chemistry, Environmental Toxicology Research Center - TOXEN, 2101, Jeanne-Mance, Montreal, Quebec H2X 2J6 (Canada)], E-mail: popovic.radovan@uqam.ca

2008-01-15

Photosynthetic-fluorescence parameters were investigated to be used as valid biomarkers of toxicity when alga Scenedesmus obliquus was exposed to isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] effect. Chlorophyll fluorescence induction of algal cells treated with isoproturon showed inactivation of photosystem II (PSII) reaction centers and strong inhibition of PSII electron transport. A linear correlation was found (R{sup 2} {>=} 0.861) between the change of cells density affected by isoproturon and the change of effective PSII quantum yield ({phi}{sub M'}), photochemical quenching (q{sub P}) and relative photochemical quenching (q{sub P(rel)}) values. The cells density was also linearly dependent (R{sup 2} = 0.838) on the relative unquenched fluorescence parameter (UQF{sub (rel)}). Non-linear correlation was found (R{sup 2} = 0.937) only between cells density and the energy transfer efficiency from absorbed light to PSII reaction center (ABS/RC). The order of sensitivity determined by the EC-50% was: UQF{sub (rel)} > {phi}{sub M'} > q{sub P} > q{sub P(rel)} > ABS/RC. Correlations between cells density and those photosynthetic-fluorescence parameters provide supporting evidence to use them as biomarkers of toxicity for environmental pollutants. - Photosynthetic-fluorescence parameters are reliable biomarkers of isoproturon toxicity.

Chlorophyll in tomato seeds: marker for seed performance?

NARCIS (Netherlands)

Suhartanto, M.R.

2002-01-01

Using Xe-PAM, laser induced fluorometry and high performance liquid chromatography we found that chlorophyll was present in young tomato (cv. Moneymaker) seeds and was degraded during maturation. Fluorescence microscopy and imaging showed that the majority of chlorophyll is located in the

Detection of residual rifampicin in urine via fluorescence quenching of gold nanoclusters on paper.

Science.gov (United States)

Chatterjee, Krishnendu; Kuo, Chiung Wen; Chen, Ann; Chen, Peilin

2015-06-26

Rifampicin or rifampin (R) is a common drug used to treat inactive meningitis, cholestatic pruritus and tuberculosis (TB), and it is generally prescribed for long-term administration under regulated dosages. Constant monitoring of rifampicin is important for controlling the side effects and preventing overdose caused by chronic medication. In this study, we present an easy to use, effective and less costly method for detecting residual rifampicin in urine samples using protein (bovine serum albumin, BSA)-stabilized gold nanoclusters (BSA-Au NCs) adsorbed on a paper substrate in which the concentration of rifampicin in urine can be detected via fluorescence quenching. The intensity of the colorimetric assay performed on the paper-based platforms can be easily captured using a digital camera and subsequently analyzed. The decreased fluorescence intensity of BSA-Au NCs in the presence of rifampicin allows for the sensitive detection of rifampicin in a range from 0.5 to 823 µg/mL. The detection limit for rifampicin was measured as 70 ng/mL. The BSA-Au NCs were immobilized on a wax-printed paper-based platform and used to conduct real-time monitoring of rifampicin in urine. We have developed a robust, cost-effective, and portable point-of-care medical diagnostic platform for the detection of rifampicin in urine based on the ability of rifampicin to quench the fluorescence of immobilized BSA-Au NCs on wax-printed papers. The paper-based assay can be further used for the detection of other specific analytes via surface modification of the BSA in BSA-Au NCs and offers a useful tool for monitoring other diseases.

Role of charge transfer and spin-orbit coupling in fluorescence quenching : a case study with oxonine and substituted benzenes

OpenAIRE

Föll, Rudolf E.; Kramer, Horst E. A.; Steiner, Ulrich

1990-01-01

Fluorescence quenching of oxonine in methanol was investigated by means of a computerized dye laser flash spectrometer for the ∆G°et, dependence of the quenching rate constant (kq) and the efficiencies of induced dye triplet formation (ηT), reduced dye radical formation (ηR), and induced internal conversion. A total of 34 substituted benzenes including 20 monohalogenated benzenes, toluenes, and anisoles were used as quenchers spanning a range of -0.85 ≤ ∆G°et ≤ 1.4 eV for a possible photoelec...

Chlorophyll b degradation by chlorophyll b reductase under high-light conditions.

Science.gov (United States)

Sato, Rei; Ito, Hisashi; Tanaka, Ayumi

2015-12-01

The light-harvesting chlorophyll a/b binding protein complex of photosystem II (LHCII) is the main antenna complex of photosystem II (PSII). Plants change their LHCII content depending on the light environment. Under high-light conditions, the content of LHCII should decrease because over-excitation damages the photosystem. Chlorophyll b is indispensable for accumulating LHCII, and chlorophyll b degradation induces LHCII degradation. Chlorophyll b degradation is initiated by chlorophyll b reductase (CBR). In land plants, NON-YELLOW COLORING 1 (NYC1) and NYC1-Like (NOL) are isozymes of CBR. We analyzed these mutants to determine their functions under high-light conditions. During high-light treatment, the chlorophyll a/b ratio was stable in the wild-type (WT) and nol plants, and the LHCII content decreased in WT plants. The chlorophyll a/b ratio decreased in the nyc1 and nyc1/nol plants, and a substantial degree of LHCII was retained in nyc1/nol plants after the high-light treatment. These results demonstrate that NYC1 degrades the chlorophyll b on LHCII under high-light conditions, thus decreasing the LHCII content. After the high-light treatment, the maximum quantum efficiency of the PSII photochemistry was lower in nyc1 and nyc1/nol plants than in WT and nol plants. A larger light-harvesting system would damage PSII in nyc1 and nyc1/nol plants. The fluorescence spectroscopy of the leaves indicated that photosystem I was also damaged by the excess LHCII in nyc1/nol plants. These observations suggest that chlorophyll b degradation by NYC1 is the initial reaction for the optimization of the light-harvesting capacity under high-light conditions.

Differences in pigment composition, photosynthetic rates and chlorophyll fluorescence images of sun and shade leaves of four tree species

Czech Academy of Sciences Publication Activity Database

Lichtenthaler, H.K.; Ač, Alexander; Marek, Michal V.; Kalina, J.; Urban, Otmar

2007-01-01

Roč. 45, č. 8 (2007), s. 577-588 ISSN 0981-9428 R&D Projects: GA ČR GP522/05/P515; GA MŽP SM/640/18/03 Institutional research plan: CEZ:AV0Z60870520 Keywords : Carbon dioxide assimilation * Chlorophyll fluorescence decrease ratio * Carotenoid level Subject RIV: ED - Physiology Impact factor: 1.669, year: 2007

Changes in chlorophyll fluorescence and photosynthetic activity of French bean leaves induced by gamma radiation

International Nuclear Information System (INIS)

Saakov, V.; Lang, M.; Schindler, C.; Stober, F.; Lichtenthaler, H.K.

1992-01-01

When exposed to gamma-radiation (12, 8 and 3.5 kGy), the growth of bean seedlings (Phaseolus vulgaris L.) was stopped and after some hours or days the plants began to wilt in a dose-dependent manner, starting from the leaf rim. The rate of the dark respiration (R) of leaves increased and that of net photosynthesis (P(N)) was strongly reduced. The regulation of stomata opening and closure was lost and the stomatal conductance (g(s)) of the gamma-ray exposed plants was strongly reduced. The reduced P(N) was only partly due to either the partial or almost full stomata closure. Chlorophyll (Chl) fluorescence measurements witha two-wavelength fluorometer and a PAM fluorometer showed an increasingly reduced variable fluorescence F(v), lower values of R(fd), of ground fluorescence F0, and of the fluorescence ratios F(v)/F(m) and F(v)/F(o). This indicated a damage to the photosynthetic apparatus. The increasing loss of photosynthetic pigments in the 350 krad exposed plants was also detected via an increase in the fluorescence ratio F690/F730. The performance of the light driven xanthophyll cycle (violaxanthin/zeaxanthin transformation) proceeded in the gamma-ray treated plants only at reduced rates. The gamma-ray damage of plants can best be detected by measurements of stomatal conductance, P(N) and various Chl fluorescence ratios such as R(fd), F(v)/F(o) and F(v)/F(m)

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.

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...

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.

Overview of remote sensing of chlorophyll flourescene in ocean waters

African Journals Online (AJOL)

Overview of remote sensing of chlorophyll flourescene in ocean waters. ... Besides empirical algorithms with the blue-green ratio, the algorithms based on ... between fluorescence and chlorophyll concentration and the red shift phenomena.

Mechanisms of photoprotection and nonphotochemical quenching in pea light-harvesting complex at 2.5 Å resolution

Science.gov (United States)

Standfuss, Jörg; Terwisscha van Scheltinga, Anke C; Lamborghini, Matteo; Kühlbrandt, Werner

2005-01-01

The plant light-harvesting complex of photosystem II (LHC-II) collects and transmits solar energy for photosynthesis in chloroplast membranes and has essential roles in regulation of photosynthesis and in photoprotection. The 2.5 Å structure of pea LHC-II determined by X-ray crystallography of stacked two-dimensional crystals shows how membranes interact to form chloroplast grana, and reveals the mutual arrangement of 42 chlorophylls a and b, 12 carotenoids and six lipids in the LHC-II trimer. Spectral assignment of individual chlorophylls indicates the flow of energy in the complex and the mechanism of photoprotection in two close chlorophyll a–lutein pairs. We propose a simple mechanism for the xanthophyll-related, slow component of nonphotochemical quenching in LHC-II, by which excess energy is transferred to a zeaxanthin replacing violaxanthin in its binding site, and dissipated as heat. Our structure shows the complex in a quenched state, which may be relevant for the rapid, pH-induced component of nonphotochemical quenching. PMID:15719016

Mechanisms of photoprotection and nonphotochemical quenching in pea light-harvesting complex at 2.5 A resolution.

Science.gov (United States)

Standfuss, Jörg; Terwisscha van Scheltinga, Anke C; Lamborghini, Matteo; Kühlbrandt, Werner

2005-03-09

The plant light-harvesting complex of photosystem II (LHC-II) collects and transmits solar energy for photosynthesis in chloroplast membranes and has essential roles in regulation of photosynthesis and in photoprotection. The 2.5 A structure of pea LHC-II determined by X-ray crystallography of stacked two-dimensional crystals shows how membranes interact to form chloroplast grana, and reveals the mutual arrangement of 42 chlorophylls a and b, 12 carotenoids and six lipids in the LHC-II trimer. Spectral assignment of individual chlorophylls indicates the flow of energy in the complex and the mechanism of photoprotection in two close chlorophyll a-lutein pairs. We propose a simple mechanism for the xanthophyll-related, slow component of nonphotochemical quenching in LHC-II, by which excess energy is transferred to a zeaxanthin replacing violaxanthin in its binding site, and dissipated as heat. Our structure shows the complex in a quenched state, which may be relevant for the rapid, pH-induced component of nonphotochemical quenching.

Temporal chlorophyll fluorescence signals to track changes in optical properties of maturing rice panicles exposed to high night temperature

Czech Academy of Sciences Publication Activity Database

Šebela, David; Quiňones, C.; Olejníčková, Julie; Jagadish, K. S. V.

2015-01-01

Roč. 177, jun (2015), s. 75-85 ISSN 0378-4290 R&D Projects: GA MŠk(CZ) LO1415; GA MŠk EE2.3.20.0246 Institutional support: RVO:67179843 Keywords : chlorophyll fluorescence (Chl-F) * grain filling * high night temperature (HNT) * maturing panicle * reflectance * Rice (Oryza sativa) Subject RIV: EH - Ecology, Behaviour Impact factor: 2.927, year: 2015

Chlorophyll Fluorescence and Reflectance-Based Non-Invasive Quantification of Blast, Bacterial Blight and Drought Stresses in Rice

Czech Academy of Sciences Publication Activity Database

Šebela, David; Quiňones, C.; Cruz, C.; Ona, I.; Olejníčková, Julie; Jagadish, K. S. V.

2018-01-01

Roč. 59, č. 1 (2018), s. 30-43 ISSN 0032-0781 R&D Projects: GA MŠk(CZ) LO1415 EU Projects: European Commission(XE) 284443 - EPPN Institutional support: RVO:86652079 Keywords : marker-assisted selection * oryza-sativa l. * water -stress * magnaporthe-grisea * disease resistance * photosynthetic efficiency * spectral reflectance * carotenoid content * eucalyptus leaves * diurnal changes * Bacterial blight * Chlorophyll fluorescence * Drought stress * Reflectance * Rice bast Subject RIV: EF - Botanics OBOR OECD: Plant sciences, botany Impact factor: 4.760, year: 2016

Differential responses of seven contrasting species to high light using pigment and chlorophyll a fluorescence

Directory of Open Access Journals (Sweden)

Mittal S.

2011-05-01

Full Text Available High light intensity may induce severe photodamage to chloroplast and consequently cause decreases in the yield capacity of plants and destruction of pigments, causing an overall yellowing of the foliage. Thus, study related to light adaptation becomes necessary to understand adaptation processes in higher plants on the basis of which they are characterized as full sunlight or shade plants. Chlorophyll can be regarded as an intrinsic fluorescent probe of the photosynthetic system. The ecophysiological parameter related to plant performance and fitness i.e. in-situ chlorophyll fluorescence measurements were determined for different plant species in the medicinal plant garden of Banasthali University, Rajasthan. Miniaturized Pulse Amplitude Modulated Photosynthetic Yield Analyzers are primarily designed for measuring effective quantum yield (ΔF/Fm’ of photosystem II under momentary ambient light in the field. Photosynthetic yield measurements and light-response curves suggested a gradation of sun-adapted to shade-adapted behaviour of these plants in following order Withania somnifera> Catharanthus roseus> Datura stamonium> Vasica minora> Vasica adulta> Rauwolfia serpentina. As indicated by light response curves and pigment analysis, Datura stramonium, Withania somnifera and Catharanthus roseus competed well photosynthetically and are favoured while Rauwolfia serpentina, Vasica minora, Vasica adulta and Plumbago zeylanica were observed to be less competent photosynthetically. These light response curves and resultant cardinal points study gave insight into the ecophysiological characterization of the photosynthetic capacity of the plant and provides highly interesting parameters like electron transport rate, photo-inhibition, photosynthetically active photon flux density and yield on the basis of which light adaptability was screened for seven medicinally important plants.

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.

Homogeneous competitive assay of ligand affinities based on quenching fluorescence of tyrosine/tryptophan residues in a protein via Főrster-resonance-energy-transfer

Science.gov (United States)

Xie, Yanling; Yang, Xiaolan; Pu, Jun; Zhao, Yunsheng; Zhang, Ying; Xie, Guoming; Zheng, Jun; Yuan, Huidong; Liao, Fei

2010-11-01

A new homogeneous competitive assay of ligand affinities was proposed based on quenching the fluorescence of tryptophan/tyrosine residues in a protein via Főrster-resonance-energy-transfer using a fluorescent reference ligand as the acceptor. Under excitation around 280 nm, the fluorescence of a protein or a bound acceptor was monitored upon competitive binding against a nonfluorescent candidate ligand. Chemometrics for deriving the binding ratio of the acceptor with either fluorescence signal was discussed; the dissociation constant ( Kd) of a nonfluorescent candidate ligand was calculated from its concentration to displace 50% binding of the acceptor. N-biotinyl-N'-(1-naphthyl)-ethylenediamine (BNEDA) and N-biotinyl-N'-dansyl-ethylenediamine (BDEDA) were used as the reference ligands and acceptors to streptavidin to test this new homogeneous competitive assay. Upon binding of an acceptor to streptavidin, there were the quench of streptavidin fluorescence at 340 nm and the characteristic fluorescence at 430 nm for BNEDA or at 525 nm for BDEDA. Kd of BNEDA and BDEDA was obtained via competitive binding against biotin. By quantifying BNEDA fluorescence, Kd of each tested nonfluorescent biotin derivative was consistent with that by quantifying streptavidin fluorescence using BNEDA or BDEDA as the acceptor. The overall coefficients of variation were about 10%. Therefore, this homogeneous competitive assay was effective and promising to high-throughput-screening.

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

Czech Academy of Sciences Publication Activity Database

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

2017-01-01

Roč. 170, Jan (2017), s. 234-241 ISSN 1386-1425 R&D Projects: GA MŠk(CZ) LO1415; GA MZe QJ1530373 Institutional support: RVO:67179843 Keywords : Raman mapping * Chlorophyll fluorescence * Carotenoids * Flavonoids * Photosynthesis * Secondary metabolites Subject RIV: EH - Ecology, Behaviour OBOR OECD: Environmental sciences (social aspects to be 5.7) Impact factor: 2.536, year: 2016

Impacts of short-term heatwaves on sun-induced chlorophyll fluorescence(SiF) in temperate tree species

Science.gov (United States)

Wang, F.; Gu, L.; Guha, A.; Han, J.; Warren, J.

2017-12-01

The current projections for global climate change forecast an increase in the intensity and frequency of extreme climatic events, such as droughts and short-term heat waves. Understanding the effects of short-term heat wave on photosynthesis process is of critical importance to predict global impacts of extreme weather event on vegetation. The diurnal and seasonal characteristics of SIF emitted from natural vegetation, e.g., forest and crop, have been studied at the ecosystem-scale, regional-scale and global-scale. However, the detailed response of SIF from different plant species under extremely weather event, especially short-term heat wave, have not been reported. The purpose of this study was to study the response of solar-induced chlorophyll fluorescence, gas exchange and continuous fluorescence at leaf scale for different temperate tree species. The short-term heatwave experiment was conducted using plant growth chamber (CMP6050, Conviron Inc., Canada). We developed an advanced spectral fitting method to obtain the plant SIF in the plant growth chamber. We compared SIF variation among different wavelength and chlorophyll difference among four temperate tree species. The diurnal variation of SIF signals at leaf-scales for temperate tree species are different under heat stress. The SIF response at leaf-scales and their difference for four temperate tree species are different during a cycle of short-term heatwave stress. We infer that SIF be used as a measure of heat tolerance for temperate tree species.

Analysis of chlorophyll fluorescence spectra for the monitoring of Cd toxicity in a bio-energy crop (Jatropha curcas).

Science.gov (United States)

Marques, Marise Conceição; do Nascimento, Clístenes Williams Araújo

2013-10-05

The vegetation of metal-contaminated soils using non-edible crops can be a safe and economical technique for Cd immobilization and the remediation of contaminated sites. Jatropha (Jatropha curcas L.) exhibits a relative tolerance to heavy metals and potential for biofuel production. The study was performed to monitor the Cd-induced alterations in jatropha plants by X-ray chlorophyll fluorescence. The Cd effects on photosynthetic pigments, the mineral composition of plants, defense enzyme activity and soluble proteins were also studied. Plants were grown for 20days in a nutrient solution with five Cd contents: 5, 10, 20, 30 and 40μmolL(-1); a control with no Cd addition was also monitored. The analysis of the chlorophyll fluorescence spectra allowed detecting alterations caused by Cd toxicity in the jatropha plants. The mineral composition of the plants was affected by the Cd doses; however, the Fe and Mg contents were not significantly reduced, which most likely improved the effects on the contents of the photosynthetic pigments. Because of its relative tolerance to Cd, Jatropha curcas may be a promising species to revegetate Cd-contaminated sites. Considering the long period needed to phytoremediate soils, the combination of remediation with bioenergy production could be an attractive option. Copyright © 2013 Elsevier B.V. All rights reserved.

[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).

Phenotyping of wheat cultivars for heat tolerance using chlorophyll a fluorescence

DEFF Research Database (Denmark)

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

2012-01-01

Abstract. In view of the global climate change, heat stress is an increasing constraint for the productivity of wheat (Triticum aestivum L.). Our aim was to identify contrasting cultivars in terms of heat tolerance by mass screening of 1274 wheat cultivars of diverse origin, based...... with a milder heat stress of 38Cin 300 mmolm–2 s–1 for 2 h with preheating at 33–35Cfor 19 h in 7–14 mmolm–2 s–1 light showed a genetic determination of 8.52.7%.Aheat treatment of 40Cin 300 mmolm–2 s–1 for 72 h in the second screening with 138 selected cultivars resulted in larger differentiation of cultivars...... with an increased genetic component (15.43.6%), which was further increased to 27.96.8% in the third screening with 41 contrasting cultivars. This contrasting set of cultivars was then used to compare the ability of chlorophyll fluorescence parameters to detect genetic difference in heat tolerance...

Evaluation of Chlorophyll fluorescence and Biochemical traits of lettuce under drought stress and super absorbent or bentonite application

OpenAIRE

GHALE BEIG AKRAM VALIZADEH; Neamati, Seyyed; Tehranifar, Ali; Emami, Hojat

2014-01-01

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 photos...

‘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 ...

Bioanalytical Applications of Fluorenscence Quenching.

Science.gov (United States)

1986-02-10

fluorescence is observed. Thus, ’ the enzymes (in this case phosphorylase C) which can hydrolyze the lecithin , can be determined by measuring the released...encapsulated in lecithin liposomes. In this manner the fluorescence is self-quenched. When the liposomes are disrupted, the dye is released and

Chlorophyll a fluorescence as a tool for a study of the Potato virus Y effects on photosynthesis of nontransgenic and transgenic Pssu-ipt tobacco

Czech Academy of Sciences Publication Activity Database

Spoustová, Petra; Synková, Helena; Valcke, R.; Čeřovská, Noemi

2013-01-01

Roč. 51, č. 2 (2013), s. 191-201 ISSN 0300-3604 Institutional research plan: CEZ:AV0Z50380511 Keywords : gas- exchange parameters * cytokinins * chlorophyll a fluorescence imaging Subject RIV: EF - Botanics Impact factor: 1.007, year: 2013

Efficacy of reduced doses of bentazone assessed by instruments based on measurement of chlorophyll fluorescence

Directory of Open Access Journals (Sweden)

Vojtěch Kocurek

2011-01-01

Full Text Available Chlorophyll fluorescence is a type of radiation emitted by plants as unused part of energy absorbed from sunlight. Its intensity depends on many stress factors, nutrition, weather conditions etc. Methods based on chlorophyll fluorescence measurement have potential to be perspective for the assessment of herbicide efficacy, phytotoxicity or stress influence. Two fluorometers (FluorCam and handy FluorPen were used for measurements in laboratory experiments in 2007–2009. Herbicide Basagran super with active ingredient bentazone (480 g.l−1 was tested using a parameter called ‚Quantum yield of fluorescence‘ (QY in three different doses: the registered dose 2.0 l.ha−1 (100% and lower doses 1.5 l.ha−1 (75% and 1.0 l.ha−1 (50%. Treated experimental plants of redroot pigweed (Amaranthus retroflexus L. were measured in 0, 1, 2, 3, 6, 9 and 15 days after treatment and the results were compared with subjective assessment (estimation and growth parameters. The obtained results showed that the effect of bentazone measured by both devices was statistically significantly different from untreated control. We can also detect herbicide effect earlier by QY measurement than by other methods. Different doses showed significant differences 15 days after treatment for dose 2.0 l.ha−1 in comparison with both reduced doses. The subjective assessment showed significant differences in all terms of measurement (1–15 days after application except of the day of application. Regeneration of plants for which the youngest leaves were not treated by herbicide was observed for all doses. Difference of QY values between used devices was on average 0.119 (higher for FluorCam but statistically insignificant.

Growth and chlorophyll fluorescence under salinity stress in sugar beet (Beta vulgaris L.

Directory of Open Access Journals (Sweden)

Fadi Abbas

2014-02-01

Full Text Available This study was carried out in the General Commission for Scientific Agricultural Research (GCSAR, Syria, at Der EzZour Agricultural Research Center, from 2008-2010, to examine the effect of salt conditions on some growth attributes and chlorophyll fluorescence in 10 Sugar Beet (Beta vulgaris L. genotypes under salinity stress. Sugar beet plants were irrigated with saline water, having electrical conductivity ranged from 8.6-10 dS.m-1during first year and 8.4-10.4 dS.m-1 during second year. A randomized completely block design with three replicates was used. The results showed that all studied growth attributes, leaf area, leaf number, relative growth rate, and net assimilation rate were decreased in salinity stress conditions compared to the controlled state. The findings indicated that salinity caused a decrement of light utilizing through increased values of fluorescence origin (fo, decreased values of fluorescence maximum (fm, and maximum yield of quantum in photosystem-II (fv/fm. Genotypes differed significantly in all studied attributes except in leaf number. Under salt conditions, Brigitta (monogerm achieved an increase in net assimilation rate, while Kawimera (multigerm achieved the lowest decrement in quantum yield in photosystem-II. Further studies are necessary to correlate the yield with yield components under similar conditions to determine the most tolerant genotype.International Journal of Environment Vol.3(1 2014: 1-9 DOI: http://dx.doi.org/10.3126/ije.v3i1.9937

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.

Determination of albumins by its quenching effect on the fluorescence of Tb3+-oxolinic acid complex in presence of sodium dodecyl sulphate

International Nuclear Information System (INIS)

Wu Xia; Zheng Jinhua; Guo Changying; Yang Jinghe; Ding Honghong; Hu Zhiyong; Li Chao

2007-01-01

It is found that the fluorescence intensity of Tb 3+ -oxolinic acid (OA) complex can be greatly quenched by albumins in sodium dodecyl sulphate (SLS). Under optimum conditions, the quenched fluorescence intensity is in proportion to the concentration of proteins in the range of 5.0x10 -8 -1.0x10 -5 g ml -1 for bovine serum albumin (BSA), 1.0x10 -7 -1.0x10 -5 g ml -1 for human serum albumin (HSA) and 4.0x10 -7 -1.0x10 -5 g ml -1 for egg albumin (EA). Their detection limits (S/N=3) are 2.1x10 -8 , 2.5x10 -8 and 5.0x10 -8 g ml -1 , respectively. In addition, the interaction mechanism is also investigated

Dead or Alive? Using Membrane Failure and Chlorophyll a Fluorescence to Predict Plant Mortality from Drought.

Science.gov (United States)

Guadagno, Carmela R; Ewers, Brent E; Speckman, Heather N; Aston, Timothy Llewellyn; Huhn, Bridger J; DeVore, Stanley B; Ladwig, Joshua T; Strawn, Rachel N; Weinig, Cynthia

2017-09-01

Climate models predict widespread increases in both drought intensity and duration in the next decades. Although water deficiency is a significant determinant of plant survival, limited understanding of plant responses to extreme drought impedes forecasts of both forest and crop productivity under increasing aridity. Drought induces a suite of physiological responses; however, we lack an accurate mechanistic description of plant response to lethal drought that would improve predictive understanding of mortality under altered climate conditions. Here, proxies for leaf cellular damage, chlorophyll a fluorescence, and electrolyte leakage were directly associated with failure to recover from drought upon rewatering in Brassica rapa (genotype R500) and thus define the exact timing of drought-induced death. We validated our results using a second genotype (imb211) that differs substantially in life history traits. Our study demonstrates that whereas changes in carbon dynamics and water transport are critical indicators of drought stress, they can be unrelated to visible metrics of mortality, i.e. lack of meristematic activity and regrowth. In contrast, membrane failure at the cellular scale is the most proximate cause of death. This hypothesis was corroborated in two gymnosperms ( Picea engelmannii and Pinus contorta ) that experienced lethal water stress in the field and in laboratory conditions. We suggest that measurement of chlorophyll a fluorescence can be used to operationally define plant death arising from drought, and improved plant characterization can enhance surface model predictions of drought mortality and its consequences to ecosystem services at a global scale. © 2017 American Society of Plant Biologists. All Rights Reserved.

A statistical analysis of the freshness of postharvest leafy vegetables with application of water based on chlorophyll fluorescence measurement

Directory of Open Access Journals (Sweden)

Yichen Qiu

2017-12-01

Full Text Available Vegetable freshness is very important for both restaurant and home consumers. In market, sellers frequently apply water to leafy vegetables to make them not lose weight and look fresh; however, these vegetables may not be stored for a long time as they appear. After a time limit, they may be quickly rotten. It is thus meaningful to investigate early and simple detection tools to measure leafy vegetable freshness while they are frequently applied water in selling. In this work, three types of newly harvested leafy vegetables were bought from a local farmer market and stored in the air with room temperature and roots submerging in water. Chlorophyll a fluorescence (ChlF from the vegetables was measured each half a day for three days. The obtained ChlF data were analyzed statistically and the correlation of ChlF parameters and vegetable freshness/storage time was obtained. The k-mean classification was also performed. It is found that Fo, Fj, Fm/Fo, and Fv/Fm can be used as an early detection tool to differentiate the freshness of leafy vegetables on which water is constantly applied in storage without visible difference. Keywords: Vegetable freshness, Chlorophyll fluorescence, Food measurement

Leaf water potential, gas exchange and chlorophyll a fluorescence in acariquara seedlings (Minquartia guianensis Aubl.) under water stress and recovery

OpenAIRE

Liberato, Maria Astrid Rocha; Gonçalves, José Francisco de Carvalho; Chevreuil, Larissa Ramos; Nina Junior, Adamir da Rocha; Fernandes, Andreia Varmes; Santos Junior, Ulysses Moreira dos

2006-01-01

The physiological performance of acariquara (Minquartia guianensis) seedlings submitted to water deficit and the recovery of physiological parameters during rehydration were investigated in a greenhouse experiment. The analyzed parameters were: leaf water potential, gas exchange and chlorophyll a fluorescence. After thirty-five days, non-irrigated plants exhibited a leaf water potential 70 % lower compared to control plants (irrigated daily) and the stomatal conductance reached values close t...

Spatio-temporal patterns of chlorophyll fluorescence and physiological and structural indices acquired from hyperspectral imagery as compared with carbon fluxes measured with eddy covariance

NARCIS (Netherlands)

Zarco-Tejada, P.J.; Morales Sierra, A.; Testi, L.; Villalobos, F.

2013-01-01

This study provides insight into the assessment of the spatio-temporal trends of chlorophyll fluorescence, narrow-band physiological indices, and structural indices acquired with a hyperspectral imager flown over a flux tower in a canopy characterized by small seasonal structural changes and a

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.

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

International Nuclear Information System (INIS)

Seedher, Neelam; Agarwal, Pooja

2010-01-01

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 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.

Wavelength-dependent ability of solar-induced chlorophyll fluorescence to estimate GPP

Science.gov (United States)

Liu, L.

2017-12-01

Recent studies have demonstrated that solar-induced chlorophyll fluorescence (SIF) can offer a new way for directly estimating the terrestrial gross primary production (GPP). In this paper, the wavelength-dependent ability of SIF to estimate GPP was investigated using both simulations by SCOPE model (Soil Canopy Observation, Photochemistry and Energy fluxes) and observations at the canopy level. Firstly, the response of the remotely sensed SIF at the canopy level to the absorbed photosynthetically active radiation (APAR ) was investigated. Both the simulations and observations confirm a linear relationship between canopy SIF and APAR, while it is species-specific and affected by biochemical components and canopy structure. The ratio of SIF to APAR varies greatly for different vegetation types, which is significant larger for canopy with horizontal structure than it with vertical structure. At red band, the ratio also decreases noticeable when chlorophyll content increases. Then, the performance of SIF to estimate GPP was investigated using diurnal observations of winter wheat at different grow stages. The results showed that the diurnal GPP could be robustly estimated from the SIF spectra for winter wheat at each growth stage, while the correlation weakened greatly at red band if all the observations made at different growth stages or all simulations with different LAI values were pooled together - a situation which did not occur at the far-red band. Finally, the SIF-based GPP models derived from the 2016 observations on winter wheat were well validated using the dataset from 2015, which give better performance for SIF at far-red band than that at red band. Therefore, it is very important to correct for reabsorption and scattering of the SIF radiative transfer from the photosystem to the canopy level before the remotely sensed SIF is linked to the GPP, especially at red band.

Exciplex formation accompanied with excitation quenching.

Science.gov (United States)

Fedorenko, Stanislav G; Burshtein, Anatoly I

2010-04-08

The competence of the reversible exciplex formation and parallel quenching of excitation (by electron or energy transfer) was considered using a non-Markovian pi-forms approach, identical to integral encounter theory (IET). General equations accounting for the reversible quenching and exciplex formation are derived in the contact approximation. Their general solution was obtained and adopted to the most common case when the ground state particles are in great excess. Particular cases of only photoionization or just exciplex formation separately studied earlier by means of IET are reproduced. In the case of the irreversible excitation quenching, the theory allows specifying the yields of the fluorescence and exciplex luminescence, as well as the long time kinetics of excitation and exciplex decays, in the absence of quenching. The theory distinguishes between the alternative regimes of (a) fast equilibration between excitations and exciplexes followed by their decay with a common average rate and (b) the fastest and deep excitation decay followed by the weaker and slower delayed fluorescence, backed by exciplex dissociation.

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

Protein disulphide isomerase is an enzyme that catalyses disulphide redox reactions in proteins. In this paper, fluorogenic and interchain disulphide bond containing peptide libraries and suitable substrates, useful in the study of protein disulphide isomerase, are described. In order to establish...... the quenching chromophore (Tyr(NO2)) and Cys(pNpys) activated for reaction with a second thiol. The formation and cleavage of the interchain disulphide bonds in the library were monitored under a fluorescence microscope. Substrates to investigate the properties of protein disulphide isomerase in solution were...

Testing the Underlying Chemical Principles of the Biotic Ligand Model (BLM) to Marine Copper Systems: Measuring Copper Speciation Using Fluorescence Quenching.

Science.gov (United States)

Tait, Tara N; McGeer, James C; Smith, D Scott

2018-01-01

Speciation of copper in marine systems strongly influences the ability of copper to cause toxicity. Natural organic matter (NOM) contains many binding sites which provides a protective effect on copper toxicity. The purpose of this study was to characterize copper binding with NOM using fluorescence quenching techniques. Fluorescence quenching of NOM with copper was performed on nine sea water samples. The resulting stability constants and binding capacities were consistent with literature values of marine NOM, showing strong binding with [Formula: see text] values from 7.64 to 10.2 and binding capacities ranging from 15 to 3110 nmol mg [Formula: see text] Free copper concentrations estimated at total dissolved copper concentrations corresponding to previously published rotifer effect concentrations, in the same nine samples, were statistically the same as the range of free copper calculated for the effect concentration in NOM-free artificial seawater. These data confirms the applicability of fluorescence spectroscopy techniques for NOM and copper speciation characterization in sea water and demonstrates that such measured speciation is consistent with the chemical principles underlying the biotic ligand model approach for bioavailability-based metals risk assessment.

Fluorescence quenching of graphene oxide combined with the site-specific cleavage of restriction endonuclease for deoxyribonucleic acid demethylase activity assay

Energy Technology Data Exchange (ETDEWEB)

Ji, Lijuan; Qian, Yingdan; Wu, Ping; Zhang, Hui; Cai, Chenxin, E-mail: cxcai@njnu.edu.cn

2015-04-15

Highlights: • An approach for sensitive and selective DNA demethylase activity assay is reported. • This assay is based on the fluorescence quenching of GO and site-specific cleavage of endonuclease. • It can determine as low as 0.05 ng mL{sup −1} of MBD2 with a linear range of 0.2–300 ng mL{sup −1}. • It has an ability to recognize MBD2 from other possibly coexisting proteins and cancer cell extracts. • It can avoid false signals, requiring no bisulfite conversion, PCR amplification, radioisotope-labeling. - Abstract: We report on the development of a sensitive and selective deoxyribonucleic acid (DNA) demethylase (using MBD2 as an example) activity assay by coupling the fluorescence quenching of graphene oxide (GO) with the site-specific cleavage of HpaII endonuclease to improve the selectivity. This approach was developed by designing a single-stranded probe (P1) that carries a binding region to facilitate the interaction with GO, which induces fluorescence quenching of the labeled fluorophore (FAM, 6-carboxyfluorescein), and a sensing region, which contains a hemi-methylated site of 5′-CmCGG-3′, to specifically recognize the target (T1, a 32-mer DNA from the promoter region of p53 gene) and hybridize with it to form a P1/T1 duplex. After demethylation with MBD2, the duplex can be specifically cleaved using HpaII, which releases the labeled FAM from the GO surface and results in the recovery of fluorescence. However, this cleavage is blocked by the hemi-methylation of this site. Thus, the magnitude of the recovered fluorescence signal is related to the MBD2 activity, which establishes the basis of the DNA demethylase activity assay. This assay can determine as low as ∼(0.05 ± 0.01) ng mL{sup −1} (at a signal/noise of 3) of MBD2 with a linear range of 0.2–300 ng mL{sup −1} and recognize MBD2 from other possibly coexisting proteins and cancer cell extracts. The advantage of this assay is its ability to avoid false signals and no

Fluorescence from gaseous UF/sub 6/ excited by a near-UV dye laser. [Decay time,quenching rate,room temperature

Energy Technology Data Exchange (ETDEWEB)

Benetti, P [Pavia Univ. (Italy); Cubeddu, R; Sacchi, C A; Svelto, O; Zaraga, F [Politecnico di Milano (Italy)

1976-06-01

Preliminary data are reported on the visible fluorescence of gaseous UF/sub 6/ excited by a dye laser at 374 nm. A decay time of 500 ns at p = 0 and a quenching rate of 5.7 x 10/sup -12/cm/sup 3/molec/sup -1/s/sup -1/ have been measured at room temperature.

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

Science.gov (United States)

Julitta, Tommaso; Corp, Lawrence A.; Rossini, Micol; Burkart, Andreas; Cogliati, Sergio; Davies, Neville; Hom, Milton; Mac Arthur, Alasdair; Middleton, Elizabeth M.; Rascher, Uwe;

Variability of sun-induced chlorophyll fluorescence according to stand age-related processes in a managed loblolly pine forest.

Science.gov (United States)

Colombo, Roberto; Celesti, Marco; Bianchi, Remo; Campbell, Petya K E; Cogliati, Sergio; Cook, Bruce D; Corp, Lawrence A; Damm, Alexander; Domec, Jean-Christophe; Guanter, Luis; Julitta, Tommaso; Middleton, Elizabeth M; Noormets, Asko; Panigada, Cinzia; Pinto, Francisco; Rascher, Uwe; Rossini, Micol; Schickling, Anke

2018-02-20

Leaf fluorescence can be used to track plant development and stress, and is considered the most direct measurement of photosynthetic activity available from remote sensing techniques. Red and far-red sun-induced chlorophyll fluorescence (SIF) maps were generated from high spatial resolution images collected with the HyPlant airborne spectrometer over even-aged loblolly pine plantations in North Carolina (United States). Canopy fluorescence yield (i.e., the fluorescence flux normalized by the light absorbed) in the red and far-red peaks was computed. This quantifies the fluorescence emission efficiencies that are more directly linked to canopy function compared to SIF radiances. Fluorescence fluxes and yields were investigated in relation to tree age to infer new insights on the potential of those measurements in better describing ecosystem processes. The results showed that red fluorescence yield varies with stand age. Young stands exhibited a nearly twofold higher red fluorescence yield than mature forest plantations, while the far-red fluorescence yield remained constant. We interpreted this finding in a context of photosynthetic stomatal limitation in aging loblolly pine stands. Current and future satellite missions provide global datasets of SIF at coarse spatial resolution, resulting in intrapixel mixture effects, which could be a confounding factor for fluorescence signal interpretation. To mitigate this effect, we propose a surrogate of the fluorescence yield, namely the Canopy Cover Fluorescence Index (CCFI) that accounts for the spatial variability in canopy structure by exploiting the vegetation fractional cover. It was found that spatial aggregation tended to mask the effective relationships, while the CCFI was still able to maintain this link. This study is a first attempt in interpreting the fluorescence variability in aging forest stands and it may open new perspectives in understanding long-term forest dynamics in response to future climatic

Gold Nanoparticle-Based Detection of Hg(II) in an Aqueous Solution: Fluorescence Quenching and Surface-Enhanced Raman Scattering Study

International Nuclear Information System (INIS)

Ganbold, Erdene Ochir; Park, Jin Ho; Ock, Kwang Su; Joo, Sang Woo

2011-01-01

We studied the detection of the Hg(II) concentration in an aqueous solution using rhodamine dyes on citrate-reduced Au nanoparticles (NPs). The quenching effect from Au NPs was found to decrease as the Hg(II) concentration increased under our experimental conditions. As the fluorescence signals intensified, the surface-enhanced Raman scattering (SERS) intensities reduced on the contrary due to less rhodamine dyes on Au NPs as the Hg(II) concentration increased. The rhodamine 6G (Rh6G) and rhodamine 123 (Rh123) dyes were examined via fluorescence and SERS measurements depending on Hg(II) concentrations. Fast and easy fluorescence detection of an Hg (II) concentration as low as a few ppm could be achieved by naked eye using citrate-reduced Au NPs

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.

Phototolerance of lichens, mosses and higher plants in an alpine environment: analysis of photoreactions.

Science.gov (United States)

Heber, U; Bilger, W; Bligny, R; Lange, O L

2000-11-01

Adaptation to excessive light is one of the requirements of survival in an alpine environment particularly for poikilohydric organisms which in contrast to the leaves of higher plants tolerate full dehydration. Changes in modulated chlorophyll fluorescence and 820-nm absorption were investigated in the lichens Xanthoria elegans (Link) Th. Fr. and Rhizocarpon geographicum (L.) DC, in the moss Grimmia alpestris Limpr. and the higher plants Geum montanum L., Gentiana lutea L. and Pisum sativum L., all collected at altitudes higher than 2000 m above sea level. In the dehydrated state, chlorophyll fluorescence was very low in the lichens and the moss, but high in the higher plants. It increased on rehydration in the lichens and the moss, but decreased in the higher plants. Light-induced charge separation in photosystem II was indicated by pulse-induced fluorescence increases only in dried leaves, not in the dry moss and dry lichens. Strong illumination caused photodamage in the dried leaves, but not in the dry moss and dry lichens. Light-dependent increases in 820-nm absorption revealed formation of potential quenchers of chlorophyll fluorescence in all dehydrated plants, but energy transfer to quenchers decreased chlorophyll fluorescence only in the moss and the lichens, not in the higher plants. In hydrated systems, coupled cyclic electron transport is suggested to occur concurrently with linear electron transport under strong actinic illumination particularly in the lichens because far more electrons became available after actinic illumination for the reduction of photo-oxidized P700 than were available in the pool of electron carriers between photosystems II and I. In the moss Grimmia, but not in the lichens or in leaves, light-dependent quenching of chlorophyll fluorescence was extensive even under nitrogen, indicating anaerobic thylakoid acidification by persistent cyclic electron transport. In the absence of actinic illumination, acidification by ca. 8% CO2 in

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...

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), 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 F v/F m 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. PMID:26101784

Energy transfer between surface-immobilized light-harvesting chlorophyll a/b complex (LHCII) studied by surface plasmon field-enhanced fluorescence spectroscopy (SPFS).

Science.gov (United States)

Lauterbach, Rolf; Liu, Jing; Knoll, Wolfgang; Paulsen, Harald

2010-11-16

The major light-harvesting chlorophyll a/b complex (LHCII) of the photosynthetic apparatus in green plants can be viewed as a protein scaffold binding and positioning a large number of pigment molecules that combines rapid and efficient excitation energy transfer with effective protection of its pigments from photobleaching. These properties make LHCII potentially interesting as a light harvester (or a model thereof) in photoelectronic applications. Most of such applications would require the LHCII to be immobilized on a solid surface. In a previous study we showed the immobilization of recombinant LHCII on functionalized gold surfaces via a 6-histidine tag (His tag) in the protein moiety. In this work the occurrence and efficiency of Förster energy transfer between immobilized LHCII on a functionalized surface have been analyzed by surface plasmon field-enhanced fluorescence spectroscopy (SPFS). A near-infrared dye was attached to some but not all of the LHC complexes, serving as an energy acceptor to chlorophylls. Analysis of the energy transfer from chlorophylls to this acceptor dye yielded information about the extent of intercomplex energy transfer between immobilized LHCII.

Chlorophyll catabolism in olive fruits (var. Arbequina and Hojiblanca) during maturation.

Science.gov (United States)

Vergara-Domínguez, Honorio; Ríos, José Julían; Gandul-Rojas, Beatriz; Roca, María

2016-12-01

The central reaction of chlorophyll (chl) breakdown pathway occurring during olive fruits maturation is the cleavage of the macrocycle pheophorbide a to a primary fluorescent chl catabolite (pFCC) and it is catalyzed by two enzymes: pheophorbide a oxygenase (PaO) and red chl catabolite reductase (RCCR). In subsequent steps, pFCC is converted to different fluorescent chlorophyll catabolites (FCCs) and nonfluorescent chlorophyll catabolites (NCCs). This work demonstrated that RCCR activity of olive fruits is type II. During the study of evolution of PaO and RCCR activities through the olive fruits maturation in two varieties: Hojiblanca and Arbequina, a significant increase in PaO and RCCR activity was found in ripening stage. In addition, the profile and structure of NCCs present in epicarp of this fruit was studied using HPLC/ESI-TOF-MS. Five different NCCs were defined and for the first time the enzymatic reactions implied in chlorophyll degradations in olive fruits elucidated. Copyright © 2016 Elsevier Ltd. All rights reserved.

Polyfluorophore Labels on DNA: Dramatic Sequence Dependence of Quenching

Science.gov (United States)

Teo, Yin Nah; Wilson, James N.

2010-01-01

We describe studies carried out in the DNA context to test how a common fluorescence quencher, dabcyl, interacts with oligodeoxynu-cleoside fluorophores (ODFs)—a system of stacked, electronically interacting fluorophores built on a DNA scaffold. We tested twenty different tetrameric ODF sequences containing varied combinations and orderings of pyrene (Y), benzopyrene (B), perylene (E), dimethylaminostilbene (D), and spacer (S) monomers conjugated to the 3′ end of a DNA oligomer. Hybridization of this probe sequence to a dabcyl-labeled complementary strand resulted in strong quenching of fluorescence in 85% of the twenty ODF sequences. The high efficiency of quenching was also established by their large Stern–Volmer constants (KSV) of between 2.1 × 104 and 4.3 × 105M−1, measured with a free dabcyl quencher. Interestingly, quenching of ODFs displayed strong sequence dependence. This was particularly evident in anagrams of ODF sequences; for example, the sequence BYDS had a KSV that was approximately two orders of magnitude greater than that of BSDY, which has the same dye composition. Other anagrams, for example EDSY and ESYD, also displayed different responses upon quenching by dabcyl. Analysis of spectra showed that apparent excimer and exciplex emission bands were quenched with much greater efficiency compared to monomer emission bands by at least an order of magnitude. This suggests an important role played by delocalized excited states of the π stack of fluorophores in the amplified quenching of fluorescence. PMID:19780115

Synthesis and characterization of new fluorescent styrene-containing carborane derivatives: the singular quenching role of a phenyl substituent.

Science.gov (United States)

Ferrer-Ugalde, Albert; Juárez-Pérez, Emilio José; Teixidor, Francesc; Viñas, Clara; Sillanpää, Reijo; Pérez-Inestrosa, Ezequiel; Núñez, Rosario

2012-01-09

A set of neutral and anionic carborane derivatives in which the styrenyl fragment is introduced as a fluorophore group has been successfully synthesized and characterized. The reaction of the monolithium salts of 1-Ph-1,2-C(2)B(10)H(11), 1-Me-1,2-C(2)B(10)H(11) and 1,2-C(2)B(10)H(12) with one equivalent of 4-vinylbenzyl chloride leads to the formation of compounds 1-3, whereas the reaction of the dilithium salt of 1,2-C(2)B(10)H(12) with two equivalents of 4-vinylbenzyl chloride gives disubstituted compound 4. The closo clusters were degraded using the classical method, KOH in EtOH, to afford the corresponding nido species, which were isolated as tetramethylammonium salts. The crystal structure of the four closo compounds 1-4 were analyzed by X-ray diffraction. All compounds, except 1, display emission properties, with quantum yields dependent on the nature of the cluster (closo or nido) and the substituent on the second C(cluster) atom. In general, closo compounds 2-4 exhibit high fluorescence emission, whereas the presence of a nido cluster produces a decrease of the emission intensity. The presence of a phenyl group bonded to the C(cluster) results in an excellent electron-acceptor unit that produces a quenching of the fluorescence. DFT calculations have confirmed the charge-separation state in 1 to explain the quenching of the fluorescence and the key role of the carboranyl fragment in this luminescent process. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rate kernel theory for pseudo-first-order kinetics of diffusion-influenced reactions and application to fluorescence quenching kinetics.

Science.gov (United States)

Yang, Mino

2007-06-07

Theoretical foundation of rate kernel equation approaches for diffusion-influenced chemical reactions is presented and applied to explain the kinetics of fluorescence quenching reactions. A many-body master equation is constructed by introducing stochastic terms, which characterize the rates of chemical reactions, into the many-body Smoluchowski equation. A Langevin-type of memory equation for the density fields of reactants evolving under the influence of time-independent perturbation is derived. This equation should be useful in predicting the time evolution of reactant concentrations approaching the steady state attained by the perturbation as well as the steady-state concentrations. The dynamics of fluctuation occurring in equilibrium state can be predicted by the memory equation by turning the perturbation off and consequently may be useful in obtaining the linear response to a time-dependent perturbation. It is found that unimolecular decay processes including the time-independent perturbation can be incorporated into bimolecular reaction kinetics as a Laplace transform variable. As a result, a theory for bimolecular reactions along with the unimolecular process turned off is sufficient to predict overall reaction kinetics including the effects of unimolecular reactions and perturbation. As the present formulation is applied to steady-state kinetics of fluorescence quenching reactions, the exact relation between fluorophore concentrations and the intensity of excitation light is derived.

[Effects of soil progressive drought during the flowering and boll-forming stage on gas exchange parameters and chlorophyll fluorescence characteristics of the subtending leaf to cotton boll].

Science.gov (United States)

Liu, Zhao-wei; Zhang, Pan; Wang, Rui; Kuai, Jie; Li, Lei; Wang, You-hua; Zhou, Zhi-guo

2014-12-01

To investigate the dynamic changes and response mechanisms of gas exchange parameters and fluorescence indices of the subtending leaf to cotton boll under soil progressive drought stress, pot experiments of the hybrid cotton No. 3 were conducted with soil relative water content (SRWC) (75 +/- 5)% as control group, SRWC (60 +/- 5)% and SRWC (45 +/- 5)% as experimental groups dealt with progressive drought for 50 days. Results showed that, the net photosynthetic rate (Pn), stomatal conductance (g(s)) and leaf intercellular CO2 concentration (Ci) decreased while Ls increased under SRWC (60 +/- 5)% for 0-21 days. Furthermore, there was no significant change in chlorophyll fluorescence indices. This indicated that stomatal limitation was the main reason for the reduction of photosynthesis of cotton. In addition, when drought for 21-49 days under SRWC (60 +/- 5)%, Pn kept decreasing, while Ci began to increase and Ls began to decrease. Potential photochemical efficiency (Fv/Fm), quantum yield of photo system II (phi(PSI)) and photochemical quenching coefficient (q(P)) reduced significantly, but non-photochemical quenching coefficient (NPQ) first rose then decreased. Thus, nonstomatal limitation was the main reason why the photosynthesis of cotton reduced. Photosynthetic organization and photosynthetic enzyme system were destroyed, boll setting intensity reduced and the number of boll and yield reduced significantly. Drought for 0-14 days under SRWC (45 +/- 5)% treatment led to sharp decrease in Pn, g(s) and Ci, whereas Ls obviously increased. There was no significant change in Fv/Fm, phi(PSII), q(P), indicating stomatal limitation was the main reason why the photosynthesis of cotton reduced. Pn decreased slowly, while Ci began to rise and Ls began to decline under SRWC (45 +/- 5)% treatment for 14-49 days. Fv/Fm, phi(PSII), q(P) decreased while NPQ rose first then declined, which indicated that nonstomatal limitation worked to reduce the cotton photosynthetic performance

Drivers and variability of the Chl fluorescence emission spectrum from the leaf through the canopy

Science.gov (United States)

Magney, T. S.; Frankenberg, C.; Grossman, K.; Koehler, P.; North, G.; Porcar-Castell, A.; Stutz, J.; Fisher, J.

2017-12-01

Recent advances in the retrieval of solar induced chlorophyll fluorescence (SIF) from remote sensing platforms provide a significant step towards mapping instantaneous plant photosynthesis across space and time. However, our current understanding of the variability and controls on the shape of the chlorophyll fluorescence (ChlF) spectrum is limited. To address these uncertainties, we have developed instrumentation to make highly resolved spectral measurements of SIF from both leaf and canopy scales. At the leaf scale, we simultaneously collected active (PAM) and passive (675-850 nm) fluorescence with photosynthesis across a range of species and conditions; and at the canopy scale, diurnal and seasonal Fraunhofer-based SIF retrievals across the red and far-red spectrum are made at four different flux tower sites (Costa Rica, Iowa (2), and Colorado). From both of these scales we are able to determine (1) the variability in steady-state spectra across species and individuals; and (2) the environmental, functional, and structural controls on SIF. Here we report on the sensitivity of SIF spectra from a singular value decomposition analysis; and present on the mechanisms - pigment concentration, species, non-photochemical and photochemical quenching, and environmental conditions - controlling SIF variability. Further, we will discuss how an improved understanding of leaf-level variability can inform canopy level SIF, and ultimately how such information may enable proper interpretation of satellite retrievals.

Exciton-controlled fluorescence: application to hybridization-sensitive fluorescent DNA probe.

Science.gov (United States)

Okamoto, Akimitsu; Ikeda, Shuji; Kubota, Takeshi; Yuki, Mizue; Yanagisawa, Hiroyuki

2009-01-01

A hybridization-sensitive fluorescent probe has been designed for nucleic acid detection, using the concept of fluorescence quenching caused by the intramolecular excitonic interaction of fluorescence dyes. We synthesized a doubly thiazole orange-labeled nucleotide showing high fluorescence intensity for a hybrid with the target nucleic acid and effective quenching for the single-stranded state. This exciton-controlled fluorescent probe was applied to living HeLa cells using microinjection to visualize intracellular mRNA localization. Immediately after injection of the probe into the cell, fluorescence was observed from the probe hybridizing with the target RNA. This fluorescence rapidly decreased upon addition of a competitor DNA. Multicoloring of this probe resulted in the simple simultaneous detection of plural target nucleic acid sequences. This probe realized a large, rapid, reversible change in fluorescence intensity in sensitive response to the amount of target nucleic acid, and facilitated spatiotemporal monitoring of the behavior of intracellular RNA.

Fluorescent quenching immune chromatographic strips with quantum dots and upconversion nanoparticles as fluorescent donors for visual detection of sulfaquinoxaline in foods of animal origin

International Nuclear Information System (INIS)

Hu, Gaoshuang; Sheng, Wei; Li, Jingmin; Zhang, Yan; Wang, Junping; Wang, Shuo

2017-01-01

In this study, two novel fluorescence quenching immune chromatographic strips (FQICS) were developed to detect sulfaquinoxaline (SQX) in foods of animal origin. These proposed FQICSs were based on fluorescence resonance energy transfer (FRET) from fluorescence donors (quantum dots or upconversion nanoparticles) to fluorescence acceptors (colloidal gold nanoparticles). Compared with traditional colloidal gold-based immune chromatographic strips (ICS), these FQICSs showed positive correlation between the fluorescent signals and the targets, and allowed user to get test results from weak fluorescent signals. The visual detection limits of these two FQICSs were both 1 ng mL −1 in standard solution and 8 μg kg −1 in samples, while the visual detection limit of the colloidal gold-based ICS was 10 ng mL −1 in standard solution and 80 μg kg −1 in samples. Besides, the results we obtained by the use of FQICS showed high agreement with those obtained by the use of commercial ELISA kits, indicating the good accuracy of these strips. As a conclusion, these proposed FQICS based on quantum dots and upconversion nanoparticles can be applied in sensitive, rapid and on-site detection of SQX in foods of animal origin. - Highlights: • Two novel FQICS based on FRET were developed for the first time. • QDs and UCNPs were used as fluorescent donors in the FQICS. • The proposed FQICS showed low LOD compared with traditional ICS. • The proposed FQICS were applied in real samples analysis. • The proposed FQICS were verified by commercial ELISA kits.

Determination of albumins by its quenching effect on the fluorescence of Tb{sup 3+}-oxolinic acid complex in presence of sodium dodecyl sulphate

Energy Technology Data Exchange (ETDEWEB)

Wu Xia [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Zheng Jinhua [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Guo Changying [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Yang Jinghe [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)]. E-mail: yjh@sdu.edu.cn; Ding Honghong [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Hu Zhiyong [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China); Li Chao [Key Laboratory of Colloid and Interface Chemistry (Shandong University), Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100 (China)

2007-09-15

It is found that the fluorescence intensity of Tb{sup 3+}-oxolinic acid (OA) complex can be greatly quenched by albumins in sodium dodecyl sulphate (SLS). Under optimum conditions, the quenched fluorescence intensity is in proportion to the concentration of proteins in the range of 5.0x10{sup -8}-1.0x10{sup -5} g ml{sup -1} for bovine serum albumin (BSA), 1.0x10{sup -7}-1.0x10{sup -5} g ml{sup -1} for human serum albumin (HSA) and 4.0x10{sup -7}-1.0x10{sup -5} g ml{sup -1} for egg albumin (EA). Their detection limits (S/N=3) are 2.1x10{sup -8}, 2.5x10{sup -8} and 5.0x10{sup -8} g ml{sup -1}, respectively. In addition, the interaction mechanism is also investigated.

Endolithic chlorophyll d-containing phototrophs

DEFF Research Database (Denmark)

Behrendt, Lars; Larkum, Anthony W D; Norman, Anders

2011-01-01

hyperspectral and variable chlorophyll fluorescence imaging, scanning electron microscopy, photopigment analysis and DNA sequencing to show that Acaryochloris-like cyanobacteria thrive underneath crustose coralline algae in a widespread endolithic habitat on coral reefs. This finding suggests an important role...

Fluorescence and Docking Studies of the Interaction between Human Serum Albumin and Pheophytin

Directory of Open Access Journals (Sweden)

Otávio Augusto Chaves

2015-10-01

Full Text Available In the North of Brazil (Pará and Amazonas states the leaves of the plant Talinum triangulare (popular: cariru replace spinach as food. From a phytochemical point of view, they are rich in compounds of the group of pheophytins. These substances, related to chlorophyll, have photophysical properties that give them potential application in photodynamic therapy. Human serum albumin (HSA is one of the main endogenous vehicles for biodistribution of molecules by blood plasma. Association constants and thermodynamic parameters for the interaction of HSA with pheophytin from Talinum triangulare were studied by UV-Vis absorption, fluorescence techniques, and molecular modeling (docking. Fluorescence quenching of the HSA’s internal fluorophore (tryptophan at temperatures 296 K, 303 K, and 310 K, resulted in values for the association constants of the order of 104 L∙mol−1, indicating a moderate interaction between the compound and the albumin. The negative values of ΔG° indicate a spontaneous process; ΔH° = 15.5 kJ∙mol−1 indicates an endothermic process of association and ΔS° = 0.145 kJ∙mol−1∙K−1 shows that the interaction between HSA and pheophytin occurs mainly by hydrophobic factors. The observed Trp fluorescence quenching is static: there is initial non-fluorescent association, in the ground state, HSA:Pheophytin. Possible solution obtained by a molecular docking study suggests that pheophytin is able to interact with HSA by means of hydrogen bonds with three lysine and one arginine residues, whereas the phytyl group is inserted in a hydrophobic pocket, close to Trp-214.

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

Directory of Open Access Journals (Sweden)

Qiuying Huang

2011-04-01

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.

A highly sensitive fluorescence quenching method for perphenazine detection based on its catalysis of K{sub 2}S{sub 2}O{sub 8} oxidizing rhodamine 6G

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lihong; Huang, Qitong; Lin, Changqing [Department of Food and Biological Engineering, Zhangzhou Institute of Technology, Zhangzhou, 363000 (China); Lin, Xiaofeng [College of Chemistry and Environment, Minnan Normal University, Zhangzhou, 363000 (China); Huang, Yiqun [Zhangzhou Affiliated Hospital of Fujian Medical University, Zhangzhou 363000 (China); Liu, Jiaming, E-mail: mnsdljm@163.com [College of Chemistry and Environment, Minnan Normal University, Zhangzhou, 363000 (China); Ma, Xudong, E-mail: maxudong005@hotmail.com [Zhangzhou Affiliated Hospital of Fujian Medical University, Zhangzhou 363000 (China)

2014-12-15

In this paper, the fluorescence spectra of Rhod 6G (rhodamine 6G)–K{sub 2}S{sub 2}O{sub 8}–PPH (perphenazine) were studied. We found that Rhod 6G existed in the form of Rhod 6G{sup +} under the conditions of 60 °C, 10 min and pH 5.42, and Rhod 6G{sup +} can emit strong and stable fluorescence. Further study showed that when PPH and Rhod 6G{sup +} coexisted, the ester exchange reaction carried out between -OH of PPH and -COOC{sub 2}H{sub 5} of Rhod 6G{sup +} to produced Rhod 6G{sup +}–PPH compound. More interestingly, K{sub 2}S{sub 2}O{sub 8} could oxidize Rhod 6G{sup +} and quench its RTP signal, while PPH was oxidized to red compound PPH′ by K{sub 2}S{sub 2}O{sub 8}, and Rhod 6G{sup +}–PPH′ and PPH were produced in the ester exchange reaction between the -OH of PPH′ and the -COOC{sub 2}H{sub 5} of Rhod 6G{sup +}–PPH. In the above process, PPH catalyzed K{sub 2}S{sub 2}O{sub 8} oxidizing Rhod 6G, which caused the fluorescence signal of the system to quench sharply. Hence, a catalytic fluorescence quenching method for the determination of residual PPH has been developed based on the its catalyzing K{sub 2}S{sub 2}O{sub 8} oxidize rhodamine 6G. This sensitive, accurate, simple and selective fluorescence quenching method was used to determine residual PPH in biological samples with the results consisting with those obtained by high performance liquid chromatography (HPLC), showing good accuracy. The structures of Rhod 6G{sup +}, PPH and Rhod 6G{sup +}–PPH were characterized by infrared spectra. The reaction mechanism of the determination of PPH was also discussed. - Highlights: • Fluorescence for the determination of perphenazine (PPH) had been established. • This method had high sensitivity (limit of detection was 3.3×10{sup −14} g mL{sup −1}). • This method had been applied to determination of PPH in biological samples. • Structures of Rhod 6G{sup +}, PPH and Rhod 6G{sup +}–PPH were characterized by infrared spectra. • Mechanism

Chiral recognition of naproxen enantiomers based on fluorescence quenching of bovine serum albumin-stabilized gold nanoclusters

Science.gov (United States)

Jafari, Marzieh; Tashkhourian, Javad; Absalan, Ghodratollah

2017-10-01

A simple, fast and green method for chiral recognition of S- and R-naproxen has been introduced. The method was based on quenching of the fluorescence intensity of bovine serum albumin-stabilized gold nanoclusters in the presence of naproxen enantiomers. The quenching intensity in the presence of S-naproxen was higher than R-naproxen when phosphate buffer solution at pH 7.0 was used. The chiral recognition occurred due to steric effect between bovine serum albumin conformation and naproxen enantiomers. Two linear determination range were established as 7.4 × 10-7-9.1 × 10-6 and 9.1 × 10-6-3.1 × 10-5 mol L-1 for both enantiomers and detection limits of 7.4 × 10-8 mol L- 1 and 9.5 × 10-8 mol L-1 were obtained for S- and R-naproxen, respectively. The developed method showed good repeatability and reproducibility for the analysis of a synthetic sample. To make the procedure applicable to biological samples, the removal of heavy metals from the sample is suggested before any analytical attempt.

Chlorophyll a fluorescence, under half of the adaptive growth-irradiance, for high-throughput sensing of leaf-water deficit in Arabidopsis thaliana accessions

Czech Academy of Sciences Publication Activity Database

Mishra, Kumud; Mishra, Anamika; Novotná, Kateřina; Rapantová, Barbora; Hodańová, Petra; Urban, Otmar

2016-01-01

Roč. 12, č. 1 (2016), č. článku 46. ISSN 1746-4811 R&D Projects: GA MŠk(CZ) LO1415; GA ČR GA13-28093S EU Projects: European Commission(XE) 284443 - EPPN Institutional support: RVO:67179843 Keywords : Chlorophyll fluorescence transients * Drought * Whole plant rosettes * Natural accessions * Non-invasive methods * Plant phenotyping Subject RIV: EH - Ecology, Behaviour Impact factor: 3.510, year: 2016

Geomagnetic and strong static magnetic field effects on growth and chlorophyll a fluorescence in Lemna minor.

Science.gov (United States)

Jan, Luka; Fefer, Dušan; Košmelj, Katarina; Gaberščik, Alenka; Jerman, Igor

2015-04-01

The geomagnetic field (GMF) varies over Earth's surface and changes over time, but it is generally not considered as a factor that could influence plant growth. The effects of reduced and enhanced GMFs and a strong static magnetic field on growth and chlorophyll a (Chl a) fluorescence of Lemna minor plants were investigated under controlled conditions. A standard 7 day test was conducted in extreme geomagnetic environments of 4 µT and 100 µT as well as in a strong static magnetic field environment of 150 mT. Specific growth rates as well as slow and fast Chl a fluorescence kinetics were measured after 7 days incubation. The results, compared to those of controls, showed that the reduced GMF significantly stimulated growth rate of the total frond area in the magnetically treated plants. However, the enhanced GMF pointed towards inhibition of growth rate in exposed plants in comparison to control, but the difference was not statistically significant. This trend was not observed in the case of treatments with strong static magnetic fields. Our measurements suggest that the efficiency of photosystem II is not affected by variations in GMF. In contrast, the strong static magnetic field seems to have the potential to increase initial Chl a fluorescence and energy dissipation in Lemna minor plants. © 2015 Wiley Periodicals, Inc.

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.

Pre-recombination quenching of the radiation induced fluorescence as the approach to study kinetics of ion-molecular reactions

International Nuclear Information System (INIS)

Borovkov, V.I.; Ivanishko, I.S.

2011-01-01

This study deals with the geminate ion recombination in the presence of bulk scavengers, that is the so-called scavenger problem, as well as with the effect of the scavenging reaction on the radiation-induced recombination fluorescence. have proposed a method to determine the rate constant of the bulk reaction between neutral scavengers and one of the geminate ions if the ion-molecular reaction prevented the formation of electronically excited states upon recombination involving a newly formed ion. If such pre-recombination quenching of the radiation-induced fluorescence took place, it manifested itself as a progressive decrease in the decay of the fluorescence intensity. The relative change in the fluorescence decay as caused by the scavengers was believed to be closely related to the kinetics of the scavenging reaction. The goal of the present study is to support this method, both computationally and experimentally because there are two factors, which cast doubt on the intuitively obvious approach to the scavenger problem: spatial correlations between the particles involved and the drift of the charged reagent in the electric field of its geminate partner. Computer simulation of geminate ions recombination with an explicit modeling of the motion trajectories of scavengers has been performed for media of low dielectric permittivity, i.e. for the maximal Coulomb interaction between the ions. The simulation has shown that upon continuous diffusion of the particles involved, the joint effect of the two above factors can be considered as insignificant with a high accuracy. Besides, it is concluded then that the method of pre-recombination quenching could be applied to study parallel and consecutive reactions where the yields of excited states in the reaction pathways are different with the use of very simple analytical relations of the formal chemical kinetics. The conclusion has been confirmed experimentally by the example of the reactions of electron transfer from

STAY-GREEN and Chlorophyll Catabolic Enzymes Interact at Light-Harvesting Complex II for Chlorophyll Detoxification during Leaf Senescence in Arabidopsis[C][W

Science.gov (United States)

Sakuraba, Yasuhito; Schelbert, Silvia; Park, So-Yon; Han, Su-Hyun; Lee, Byoung-Doo; Andrès, Céline Besagni; Kessler, Felix; Hörtensteiner, Stefan; Paek, Nam-Chon

2012-01-01

During leaf senescence, plants degrade chlorophyll to colorless linear tetrapyrroles that are stored in the vacuole of senescing cells. The early steps of chlorophyll breakdown occur in plastids. To date, five chlorophyll catabolic enzymes (CCEs), NONYELLOW COLORING1 (NYC1), NYC1-LIKE, pheophytinase, pheophorbide a oxygenase (PAO), and red chlorophyll catabolite reductase, have been identified; these enzymes catalyze the stepwise degradation of chlorophyll to a fluorescent intermediate, pFCC, which is then exported from the plastid. In addition, STAY-GREEN (SGR), Mendel’s green cotyledon gene encoding a chloroplast protein, is required for the initiation of chlorophyll breakdown in plastids. Senescence-induced SGR binds to light-harvesting complex II (LHCII), but its exact role remains elusive. Here, we show that all five CCEs also specifically interact with LHCII. In addition, SGR and CCEs interact directly or indirectly with each other at LHCII, and SGR is essential for recruiting CCEs in senescing chloroplasts. PAO, which had been attributed to the inner envelope, is found to localize in the thylakoid membrane. These data indicate a predominant role for the SGR-CCE-LHCII protein interaction in the breakdown of LHCII-located chlorophyll, likely to allow metabolic channeling of phototoxic chlorophyll breakdown intermediates upstream of nontoxic pFCC. PMID:22366162

Fluorescence quenching studies of potential-dependent DNA reorientation dynamics at glassy carbon electrode surfaces.

Science.gov (United States)

Li, Qin; Cui, Chenchen; Higgins, Daniel A; Li, Jun

2012-09-05

The potential-dependent reorientation dynamics of double-stranded DNA (ds-DNA) attached to planar glassy carbon electrode (GCE) surfaces were investigated. The orientation state of surface-bound ds-DNA was followed by monitoring the fluorescence from a 6-carboxyfluorescein (FAM6) fluorophore covalently linked to the distal end of the DNA. Positive potentials (i.e., +0.2 V vs open circuit potential, OCP) caused the ds-DNA to align parallel to the electrode surface, resulting in strong dipole-electrode quenching of FAM6 fluorescence. Switching of the GCE potential to negative values (i.e., -0.2 V vs OCP) caused the ds-DNA to reorient perpendicular to the electrode surface, with a concomitant increase in FAM6 fluorescence. In addition to the very fast (submilliseconds) dynamics of the initial reorientation process, slow (0.1-0.9 s) relaxation of FAM6 fluorescence to intermediate levels was also observed after potential switching. These dynamics have not been previously described in the literature. They are too slow to be explained by double layer charging, and chronoamperometry data showed no evidence of such effects. Both the amplitude and rate of the dynamics were found to depend upon buffer concentration, and ds-DNA length, demonstrating a dependence on the double layer field. The dynamics are concluded to arise from previously undetected complexities in the mechanism of potential-dependent ds-DNA reorientation. The possible origins of these dynamics are discussed. A better understanding of these dynamics will lead to improved models for potential-dependent ds-DNA reorientation at electrode surfaces and will facilitate the development of advanced electrochemical devices for detection of target DNAs.

Short range photoinduced electron transfer in proteins: QM-MM simulations of tryptophan and flavin fluorescence quenching in proteins

International Nuclear Information System (INIS)

Callis, Patrik R.; Liu Tiqing

2006-01-01

Hybrid quantum mechanical-molecular mechanics (dynamics) were performed on flavin reductase (Fre) and flavodoxin reductase (Fdr), both from Escherichia coli. Each was complexed with riboflavin (Rbf) or flavin mononucleotide (FMN). During 50 ps trajectories, the relative energies of the fluorescing state (S 1 ) of the isoalloxazine ring and the lowest charge transfer state (CT) were assessed to aid prediction of fluorescence lifetimes that are shortened due to quenching by electron transfer from tyrosine. The simulations for the four cases display a wide range in CT-S 1 energy gap caused by the presence of phosphate, other charged and polar residues, water, and by intermolecular separation between donor and acceptor. This suggests that the Gibbs energy change (ΔG 0 ) and reorganization energy (λ) for the electron transfer may differ in different flavoproteins

Sensitive detection of copper ions via ion-responsive fluorescence quenching of engineered porous silicon nanoparticles

Science.gov (United States)

Hwang, Jangsun; Hwang, Mintai P.; Choi, Moonhyun; Seo, Youngmin; Jo, Yeonho; Son, Jaewoo; Hong, Jinkee; Choi, Jonghoon

2016-10-01

Heavy metal pollution has been a problem since the advent of modern transportation, which despite efforts to curb emissions, continues to play a critical role in environmental pollution. Copper ions (Cu2+), in particular, are one of the more prevalent metals that have widespread detrimental ramifications. From this perspective, a simple and inexpensive method of detecting Cu2+ at the micromolar level would be highly desirable. In this study, we use porous silicon nanoparticles (NPs), obtained via anodic etching of Si wafers, as a basis for undecylenic acid (UDA)- or acrylic acid (AA)-mediated hydrosilylation. The resulting alkyl-terminated porous silicon nanoparticles (APS NPs) have enhanced fluorescence stability and intensity, and importantly, exhibit [Cu2+]-dependent quenching of fluorescence. After determining various aqueous sensing conditions for Cu2+, we demonstrate the use of APS NPs in two separate applications - a standard well-based paper kit and a portable layer-by-layer stick kit. Collectively, we demonstrate the potential of APS NPs in sensors for the effective detection of Cu2+.

Chlorophyll and its degradation products in the two-spotted spider mite, Tetranychus urticae: observations using epifluorescence and confocal laser scanning microscopy.

Science.gov (United States)

Occhipinti, Andrea; Maffei, Massimo E

2013-10-01

Chlorophyll and chlorophyll degradation products were observed in the two-spotted spider mite (Tetranychus urticae) using epifluorescence microscopy (EFM) and confocal laser scanning microscopy (CLSM). A clear red fluorescence (EFM) and a fluorescence induced by a laser wavelength of 650 nm (CLSM) were observed. In the lateral caeca, in the ventriculus and in the excretory organ, a bright light blue fluorescence was observed in close association with chlorophyll by using EFM. The same material can be localized with CLSM by using a laser with a wavelength of 488 nm. By comparison with synthetic guanine, this bright fluorescence is supposed to be guanine. The presence of guanine fluorescence in the mite pellets confirms this hypothesis. A possible mechanism for guanine formation is discussed.

Effect of Drought Stress and Methanol on Chlorophyll Parameters, Chlorophyll Content and Relative Water Content of Soybean (Glycine max L., var. L 17

Directory of Open Access Journals (Sweden)

M Mirakhori

2011-01-01

Full Text Available Abstract In order to investigate the effects of methanol application on some physiological properties of soybean under low water stress, a factorial experiment was conducted at Research Field of Faculty of Agriculture and Natural Resources, Islamic Azad University-Karaj Branch, Karaj, Iran, during 2008, based on a randomized complete block design with three replications. The first factor was consisted of different levels of methanol equal to 0 (control, 7, 14, 21, 28 and 35 volumetric percentage (v/v, which were used as foliar applications at three times during growth season of soybean, with 15 days intervals. The second factor was water stress conditions in two levels, based on depletion of 40 and 70% of available soil moisture. Some traits such as grain yield (GY, relative water content (RWC, chlorophyll fluorescence parameters, and chlorophyll content were measured, one day before and after the third methanol application. Results showed that chlorophyll content (Chl, GY, electrolytes leakage (EL at second sampling, photochemical capacity of PSII (Fv/Fm, maximum and variable fluorescence (Fm and FV, respectively were affected by water stress significantly (p

UPSCALING OF SOLAR INDUCED CHLOROPHYLL FLUORESCENCE FROM LEAF TO CANOPY USING THE DART MODEL AND A REALISTIC 3D FOREST SCENE

Directory of Open Access Journals (Sweden)

W. Liu

2017-10-01

Full Text Available Solar induced chlorophyll a fluorescence (SIF has been shown to be an excellent proxy of photosynthesis at multiple scales. However, the mechanical linkages between fluorescence and photosynthesis at the leaf level cannot be directly applied at canopy or field scales, as the larger scale SIF emission depends on canopy structure. This is especially true for the forest canopies characterized by high horizontal and vertical heterogeneity. While most of the current studies on SIF radiative transfer in plant canopies are based on the assumption of a homogeneous canopy, recently codes have been developed capable of simulation of fluorescence signal in explicit 3-D forest canopies. Here we present a canopy SIF upscaling method consisting of the integration of the 3-D radiative transfer model DART and a 3-D object model BLENDER. Our aim was to better understand the effect of boreal forest canopy structure on SIF for a spatially explicit forest canopy.

Salinity reduced growth PS2 photochemistry and chlorophyll content in radish Crescimento reduzido por salinidade, fotoquímica PS2 e conteúdo de clorofila em rabanete

Directory of Open Access Journals (Sweden)

Muhammad Jamil

2007-01-01

Full Text Available When plants are grown under saline conditions, photosynthetic activity decreases leading to reduced plant growth, leaf area, chlorophyll content and chlorophyll fluorescence. Seeds and seedlings of radish (Raphanus sativus L. were grown in NaCl solutions under controlled greenhouse conditions. The NaCl concentrations in complete nutrient solutions were 0 (control, 4.7, 9.4 and 14.1 dS m-1. The salinity reduced germination percentage and also delayed the germination rate as the salt level increased. Lengths and fresh weights of root and shoot decreased with the increasing salt concentration. Furthermore, photochemical efficiency of PS2 (Fv/Fm, photochemical quenching coefficient (qP, non photochemical quenching coefficient (qN, leaf area and chlorophyll content (SPAD value were also reduced (P Quando plantas crescem sob condições de salinidade, sua atividade fotossintética diminui levando a um crescimento reduzido, menor área foliar, conteúdo de clorofila e fluorescência de clorofila. Sementes e plântulas de rabanete (Raphanus sativus L. foram germinadas e conduzidas em soluções de NaCl sob condições controladas de casa de vegetação. As concentrações de NaCl adicionado a solução nutritiva completa foram 0 (Controle, 4,7; 9,4 e 14,1 dS m-1. A salinidade diminui a percentagem de germinação e também atrasou a taxa de germinação com o aumento do nível de sal. Comprimento e peso fresco da parte aérea e da raiz decresceram com o aumento da concentração salina. Além disso, a eficiência fotoquímica de PS2 (Fv/Fm, o coeficiente fotoquímico de 'quenchin" (q p, o coeficiente não fotoquímico de "quenching" (q n, a área foliar e o teor de clorofila (valor SPAD também foram reduzidos (P < 0,001 por estresse de sal. Ao contrário, a relação Fo/Fm aumentou com a concentração salina, ao passo que a salinidade não teve efeito sobre a eficiência de excitação capturada pelo PS2 aberto (Fv'/Fm', taxa de transporte eletr

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.

Mercury effects on Thalassiosira weissflogii: Applications of two-photon excitation chlorophyll fluorescence lifetime imaging and flow cytometry

International Nuclear Information System (INIS)

Wu Yun; Zeng Yan; Qu, Jianan Y.; Wang Wenxiong

2012-01-01

The toxic effects of inorganic mercury [Hg(II)] and methylmercury (MeHg) on the photosynthesis and population growth in a marine diatom Thalassiosira weissflogii were investigated using two methods: two-photon excitation fluorescence lifetime imaging (FLIM) and flow cytometry (FCM). For photosynthesis, Hg(II) exposure increased the average chlorophyll fluorescence lifetime, whereas such increment was not found under MeHg stress. This may be caused by the inhibitory effect of Hg(II) instead of MeHg on the electron transport chain. For population growth, modeled specific growth rate data showed that the reduction in population growth by Hg(II) mainly resulted from an increased number of injured cells, while the live cells divided at the normal rates. However, MeHg inhibitory effects on population growth were contributed by the reduced division rates of all cells. Furthermore, the cell images and the FCM data reflected the morphological changes of diatom cells under Hg(II)/MeHg exposure vividly and quantitatively. Our results demonstrated that the toxigenicity mechanisms between Hg(II) and MeHg were different in the algal cells.

Relationship between leaf optical properties, chlorophyll fluorescence and pigment changes in senescing Acer saccharum leaves.

Science.gov (United States)

Junker, Laura Verena; Ensminger, Ingo

2016-06-01

The ability of plants to sequester carbon is highly variable over the course of the year and reflects seasonal variation in photosynthetic efficiency. This seasonal variation is most prominent during autumn, when leaves of deciduous tree species such as sugar maple (Acer saccharum Marsh.) undergo senescence, which is associated with downregulation of photosynthesis and a change of leaf color. The remote sensing of leaf color by spectral reflectance measurements and digital repeat images is increasingly used to improve models of growing season length and seasonal variation in carbon sequestration. Vegetation indices derived from spectral reflectance measurements and digital repeat images might not adequately reflect photosynthetic efficiency of red-senescing tree species during autumn due to the changes in foliar pigment content associated with autumn phenology. In this study, we aimed to assess how effectively several widely used vegetation indices capture autumn phenology and reflect the changes in physiology and photosynthetic pigments during autumn. Chlorophyll fluorescence and pigment content of green, yellow, orange and red leaves were measured to represent leaf senescence during autumn and used as a reference to validate and compare vegetation indices derived from leaf-level spectral reflectance measurements and color analysis of digital images. Vegetation indices varied in their suitability to track the decrease of photosynthetic efficiency and chlorophyll content despite increasing anthocyanin content. Commonly used spectral reflectance indices such as the normalized difference vegetation index and photochemical reflectance index showed major constraints arising from a limited representation of gradual decreases in chlorophyll content and an influence of high foliar anthocyanin levels. The excess green index and green-red vegetation index were more suitable to assess the process of senescence. Similarly, digital image analysis revealed that vegetation

Loss of Functional Photosystem II Reaction Centres in Zooxanthellae of Corals Exposed to Bleaching Conditions: Using Fluorescence Rise Kinetics.

Science.gov (United States)

Hill, R; Larkum, A W D; Frankart, C; Kühl, M; Ralph, P J

2004-01-01

Mass coral bleaching is linked to elevated sea surface temperatures, 1-2 degrees C above average, during periods of intense light. These conditions induce the expulsion of zooxanthellae from the coral host in response to photosynthetic damage in the algal symbionts. The mechanism that triggers this release has not been clearly established and to further our knowledge of this process, fluorescence rise kinetics have been studied for the first time. Corals that were exposed to elevated temperature (33 degrees C) and light (280 mumol photons m(-2) s(-1)), showed distinct changes in the fast polyphasic induction of chlorophyll-a fluorescence, indicating biophysical changes in the photochemical processes. The fluorescence rise over the first 2000ms was monitored in three species of corals for up to 8 h, with a PEA fluorometer and an imaging-PAM. Pocillopora damicornis showed the least impact on photosynthetic apparatus, while Acropora nobilis was the most sensitive, with Cyphastrea serailia intermediate between the other two species. A. nobilis showed a remarkable capacity for recovery from bleaching conditions. For all three species, a steady decline in the slope of the initial rise and the height of the J-transient was observed, indicating the loss of functional Photosystem II (PS II) centres under elevated-temperature conditions. A significant loss of PS II centres was confirmed by a decline in photochemical quenching when exposed to bleaching stress. Non-photochemical quenching was identified as a significant mechanism for dissipating excess energy as heat under the bleaching conditions. Photophosphorylation could explain this decline in PS II activity. State transitions, a component of non-photochemical quenching, was a probable cause of the high non-photochemical quenching during bleaching and this mechanism is associated with the phosphorylation-induced dissociation of the light harvesting complexes from the PS II reaction centres. This reversible process may

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.

Loss of the precise control of photosynthesis and increased yield of non-radiative dissipation of exitation energy after mild heat treatment of barley leaves

International Nuclear Information System (INIS)

Bukhov, N.G.; Boucher, N.; Carpentier, R.

1998-01-01

The after effects of a short exposure of intact barley leaves to moderately elevated temperature (40°C, 5 min) on the induction transients and the irradiance dependencies of photosynthesis and chlorophyll fluorescence are presented. This mild heat treatment strongly reduced the oscillations in the rate of photosynthesis and in the yield of chlorophyll fluorescence. However, only a 25% irreversible inhibition of maximum photosynthetic capacity of photosystem II (PSII) measured by oxygen evolution was produced and the intrinsic quantum yield of PSII measured by the chlorophyll fluorescence ratio (F m - F o )/Fm decreased by only 15%. In contrast, the above treatment increased radiationless dissipation processes in PSII by a factor of two. In heat-treated leaves, photosynthesis was not saturated even by strong light. Both ΔpH-dependent quenching of excitons in PSII (including formation of zeaxanthin) and state 1/state 2 transition were found to be stimulated. Heat exposure enhanced the control of PSII activity by PSI, as evidenced by a significant increase in the quenching effect of far-red light on the maximum yield of chlorophyll fluorescence. It was deduced that after mild heat treatment, the photosynthetic apparatus in leaves lacks the precise coordinating control of electron transport and carbon metabolism owing to the inability of PSII to support electron transport at a level adequate for carbon metabolism. This effect was not related to the small irreversible thermal damage to PSII, but was rather due to a significant increase in non-photochemical quenching of excitation energy. (author)

Fluoresence quenching of riboflavin in aqueous solution by methionin and cystein

International Nuclear Information System (INIS)

Droessler, P.; Holzer, W.; Penzkofer, A.; Hegemann, P.

2003-01-01

The fluorescence quantum distributions, fluorescence quantum yields, and fluorescence lifetimes of riboflavin in methanol, DMSO, water, and aqueous solutions of the sulphur atom containing amino acids methionin and cystein have been determined. In methanol, DMSO, and water (pH=4-8) only dynamic fluorescence reduction due to intersystem crossing and internal conversion is observed. In aqueous methionin solutions of pH=5.25-9 a pH independent static and dynamic fluorescence quenching occurs probably due to riboflavin anion-methionin cation pair formation. In aqueous cystein solutions (pH range from 4.15 to 9) the fluorescence quenching increases with rising pH due to cystein thiolate formation. The cystein thiol form present at low pH does not react with neutral riboflavin. Cystein thiolate present at high pH seems to react with neutral riboflavin causing riboflavin deprotonation (anion formation) by cystein thiolate reduction to the cystein thiol form

Ultratrace analysis of transuranic actinides by laser-induced fluorescence

Science.gov (United States)

Miller, S.M.

1983-10-31

Ultratrace quantities of transuranic actinides are detected indirectly by their effect on the fluorescent emissions of a preselected fluorescent species. Transuranic actinides in a sample are coprecipitated with a host lattice material containing at least one preselected fluorescent species. The actinide either quenches or enhances the laser-induced fluorescence of the preselected fluorescent species. The degree of enhancement or quenching is quantitatively related to the concentration of actinide in the sample.

Quenching-free fluorescence signal from plastic-fibres in proton dosimetry: understanding the influence of Čerenkov radiation

DEFF Research Database (Denmark)

Christensen, Jeppe Brage; Almhagen, Erik; Nyström, Håkan

2018-01-01

The origin of photons emitted in optical fibres under proton irradiation has been attributed to either entirely Čerenkov radiation or light consisting of fluorescence with a substantial amount of Čerenkov radiation. The source of the light emission is assessed in order to understand why the signal...... from optical fibres irradiated with protons is reportedly quenching-free. The present study uses the directional emittance of Čerenkov photons in 12 MeV and 20 MeV electron beams to validate a Monte Carlo model for simulating the emittance and transmission of Čerenkov radiation in optical fibres. We...

Gold and silver nanoparticles based superquenching of fluorescence: A review

Energy Technology Data Exchange (ETDEWEB)

Ghosh, Debanjana; Chattopadhyay, Nitin, E-mail: nitin.chattopadhyay@yahoo.com

2015-04-15

The short review highlights the recent advances on the gold and silver nanoparticles induced efficient quenching of fluorescence from various fluorophores looking at their promising use as optical rulers and chemo-/bio- sensors. The fluorescence quenching often leads to the increase in the Stern–Volmer constant (K{sub SV}~10{sup 7}–10{sup 10} mol{sup −1} dm{sup 3}) several orders of magnitude higher than the values observed for the normal photochemical quenching processes (~10{sup 2} mol{sup −1} dm{sup 3}). This amplified quenching has been termed as “super-quenching” or “hyper-quenching”. Energy transfer (ET) is established from the donor to the metal nanoparticles rationalizing these fast quenching processes. Considering the distance dependence of the ET process, Förster resonance energy transfer (FRET) and nanometal surface energy transfer (NSET) are ascribed to take place. These sensitive distance dependent phenomena serve as the spectroscopic ruler to measure the intra- or intermolecular distances between the interacting partners. In this account focus has been laid on the size dependent energy transfer and super- and hyper- quenching of the fluorescence of the donor moieties by the nanometals and their probable applications in sensing. Rationalization has been made for the nanoparticle induced huge enhancement in the quenching efficiency. The impact of this review lies in the possible application of these amplified quenching processes in designing high sensitive chemical and biological sensors. - Highlights: • Super efficient quenching of fluorescence of probes by gold and silver nanoparticles is highlighted. • The amplified fluorescence quenching of dyes and polymers is rationalized. • Energy transfer is assigned to be responsible for the efficient quenching process. • Amplified quenching has its potential use in designing sensitive chemical/biological sensors.

Gold and silver nanoparticles based superquenching of fluorescence: A review

International Nuclear Information System (INIS)

Ghosh, Debanjana; Chattopadhyay, Nitin

2015-01-01

The short review highlights the recent advances on the gold and silver nanoparticles induced efficient quenching of fluorescence from various fluorophores looking at their promising use as optical rulers and chemo-/bio- sensors. The fluorescence quenching often leads to the increase in the Stern–Volmer constant (K SV ~10 7 –10 10 mol −1 dm 3 ) several orders of magnitude higher than the values observed for the normal photochemical quenching processes (~10 2 mol −1 dm 3 ). This amplified quenching has been termed as “super-quenching” or “hyper-quenching”. Energy transfer (ET) is established from the donor to the metal nanoparticles rationalizing these fast quenching processes. Considering the distance dependence of the ET process, Förster resonance energy transfer (FRET) and nanometal surface energy transfer (NSET) are ascribed to take place. These sensitive distance dependent phenomena serve as the spectroscopic ruler to measure the intra- or intermolecular distances between the interacting partners. In this account focus has been laid on the size dependent energy transfer and super- and hyper- quenching of the fluorescence of the donor moieties by the nanometals and their probable applications in sensing. Rationalization has been made for the nanoparticle induced huge enhancement in the quenching efficiency. The impact of this review lies in the possible application of these amplified quenching processes in designing high sensitive chemical and biological sensors. - Highlights: • Super efficient quenching of fluorescence of probes by gold and silver nanoparticles is highlighted. • The amplified fluorescence quenching of dyes and polymers is rationalized. • Energy transfer is assigned to be responsible for the efficient quenching process. • Amplified quenching has its potential use in designing sensitive chemical/biological sensors

Rapid and accurate determination of Stern-Volmer quenching constants

International Nuclear Information System (INIS)

Goodpaster, John V.; McGuffin, Victoria L.

1999-01-01

In this work, a novel system has been designed, characterized, and validated for the determination of fluorescence quenching constants. Capillary flow injection methods are used to automate the preparation and mixing of the fluorophore and quencher solutions. Because of the small diameter of the capillary (75-200 μm), fluorescence measurements can be made without corrections for primary and secondary absorbance effects. The fluorescence spectrometer is equipped with a charge-coupled device (CCD) that has a detection limit of 3.0x10 -9 M (2.3 ppb) and a linear dynamic range of 10 5 for integration times of 0.01-10 s. This spectrometer has a 300 nm spectral range with 1 nm resolution, allowing the fluorescence quenching constants to be calculated at single wavelengths or over integrated wavelength ranges. This system was validated by comparison to traditional methods for the determination of Stern-Volmer constants for alternant and nonalternant polycyclic aromatic hydrocarbons with nitromethane and triethylamine. (c) 2000 Society for Applied Spectroscopy

Mapping Hfq-RNA interaction surfaces using tryptophan fluorescence quenching

Science.gov (United States)

Robinson, Kirsten E.; Orans, Jillian; Kovach, Alexander R.; Link, Todd M.; Brennan, Richard G.

2014-01-01

Hfq is a posttranscriptional riboregulator and RNA chaperone that binds small RNAs and target mRNAs to effect their annealing and message-specific regulation in response to environmental stressors. Structures of Hfq-RNA complexes indicate that U-rich sequences prefer the proximal face and A-rich sequences the distal face; however, the Hfq-binding sites of most RNAs are unknown. Here, we present an Hfq-RNA mapping approach that uses single tryptophan-substituted Hfq proteins, all of which retain the wild-type Hfq structure, and tryptophan fluorescence quenching (TFQ) by proximal RNA binding. TFQ properly identified the respective distal and proximal binding of A15 and U6 RNA to Gram-negative Escherichia coli (Ec) Hfq and the distal face binding of (AA)3A, (AU)3A and (AC)3A to Gram-positive Staphylococcus aureus (Sa) Hfq. The inability of (GU)3G to bind the distal face of Sa Hfq reveals the (R-L)n binding motif is a more restrictive (A-L)n binding motif. Remarkably Hfq from Gram-positive Listeria monocytogenes (Lm) binds (GU)3G on its proximal face. TFQ experiments also revealed the Ec Hfq (A-R-N)n distal face-binding motif should be redefined as an (A-A-N)n binding motif. TFQ data also demonstrated that the 5′-untranslated region of hfq mRNA binds both the proximal and distal faces of Ec Hfq and the unstructured C-terminus. PMID:24288369

A novel single fluorophore-labeled double-stranded oligonucleotide probe for fluorescence-enhanced nucleic acid detection based on the inherent quenching ability of deoxyguanosine bases and competitive strand-displacement reaction.

Science.gov (United States)

Zhang, Yingwei; Tian, Jingqi; Li, Hailong; Wang, Lei; Sun, Xuping

2012-01-01

We develop a novel single fluorophore-labeled double-stranded oligonucleotide (OND) probe for rapid, nanostructure-free, fluorescence-enhanced nucleic acid detection for the first time. We further demonstrate such probe is able to well discriminate single-base mutation in nucleic acid. The design takes advantage of an inherent quenching ability of guanine bases. The short strand of the probe is designed with an end-labeled fluorophore that is placed adjacent to two guanines as the quencher located on the long opposite strand, resulting in great quenching of dye fluorescence. In the presence of a target complementary to the long strand of the probe, a competitive strand-displacement reaction occurs and the long strand forms a more stable duplex with the target, resulting in the two strands of the probe being separated from each other. As a consequence of this displacement, the fluorophore and the quencher are no longer in close proximity and dye fluorescence increases, signaling the presence of target.

Hyperspectral and Chlorophyll Fluorescence Imaging to Analyse the Impact of Fusarium culmorum on the Photosynthetic Integrity of Infected Wheat Ears

Directory of Open Access Journals (Sweden)

Werner B. Herppich

2011-03-01

Full Text Available Head blight on wheat, caused by Fusarium spp., is a serious problem for both farmers and food production due to the concomitant production of highly toxic mycotoxins in infected cereals. For selective mycotoxin analyses, information about the on-field status of infestation would be helpful. Early symptom detection directly on ears, together with the corresponding geographic position, would be important for selective harvesting. Hence, the capabilities of various digital imaging methods to detect head blight disease on winter wheat were tested. Time series of images of healthy and artificially Fusarium-infected ears were recorded with a laboratory hyperspectral imaging system (wavelength range: 400 nm to 1,000 nm. Disease-specific spectral signatures were evaluated with an imaging software. Applying the ‘Spectral Angle Mapper’ method, healthy and infected ear tissue could be clearly classified. Simultaneously, chlorophyll fluorescence imaging of healthy and infected ears, and visual rating of the severity of disease was performed. Between six and eleven days after artificial inoculation, photosynthetic efficiency of infected compared to healthy ears decreased. The severity of disease highly correlated with photosynthetic efficiency. Above an infection limit of 5% severity of disease, chlorophyll fluorescence imaging reliably recognised infected ears. With this technique, differentiation of the severity of disease was successful in steps of 10%. Depending on the quality of chosen regions of interests, hyperspectral imaging readily detects head blight 7 d after inoculation up to a severity of disease of 50%. After beginning of ripening, healthy and diseased ears were hardly distinguishable with the evaluated methods.

Fluorescence spectral properties of outer antenna LHC II

CERN Document Server

He Jun Fang; Zhang, Shu; He Fang Tao; Ren Zhao You; Li Liang Bi; Kuang Ting Yun

2002-01-01

Outer antenna LHC II acts to absorb and transfer energy for photosynthesis. The authors studied the fluorescence properties of LHC II of spinach with scanning imaging fluorescence spectroscopy. After it had been excited by 514.5 nm laser, the integral fluorescence spectrum of LHC II was detected. It was shown that energy transfer existed between carotenoid and chlorophyll. Seven bands of LHC II fluorescence emission were resolved by Gauss combination, viz. 656.7, 664.6, 671.5, 677.2, 683.5, 689.6, 695.3 nm, and the percentages of them were 3.0%, 13.1%,13.3%, 21.1%, 13.2%, 33.3%, 3.0% respectively. The emission of 658.7 nm was attributed to chlorophyll b, the other emission bands were produced by chlorophyll a molecules with the maximum absorption 662, 670/671, 676, 680 nm and over 690 nm. The band 656.7 nm, whose percentage was 3.0%, shows that the most energy was absorbed by chlorophyll a. The percentage of band 689.6 nm was the most, which was possibly correlated with one type of self protective mechanism o...

Changes of the laser-induced blue, green and red fluorescence signatures during greening of etiolated leaves of wheat

International Nuclear Information System (INIS)

Stober, F.; Lichtenthaler, H.K.

1992-01-01

The UV-laser-induced blue, green and red fluorescence-emission spectra were used to characterize the pigment status of etiolated leaves of wheat (Triticum aestivum L.) during a 48 h greening period under white light conditions. Upon UV-light excitation (337 nm) leaves not only show a fluorescence emission in the red spectral region between 650 and 800nm (chlorophyll fluorescence with maxima near 690nm and 735 nm), but also in the blue and green regions between 400 to 570 nm with maxima or shoulders near 450 nm (blue) and 530 nm (green). During greening of etiolated leaves the chlorophyll-fluorescence ratio F690/F735 strongly correlated with the total chlorophyll content and the ratio of the chlorophylls to the carotenoids (a+b/x+c). The ratio of the blue to the green fluorescence F450/F530 was also correlated with the total chlorophyll content and the ratio of chlorophylls to total carotenoids (a+b/x+c). Consequently, there also existed a correlation between the chlorophyll-fluorescence ratio F690/F735 and the ratio of the blue to green fluorescence F450/F530. In contrast, the ratios of the blue to red fluorescences F450/F690 and F450/F735 did not show clear relations to the pigment content of the investigated plants. The particular shape of the UV-laser-induced-fluorescence emission spectra of wheat leaves as well as the dependencies of the fluorescence ratios on the pigment content are due to a partial and differential reabsorption of the emitted fluorescences by the photosynthetic pigments

Diurnal Variability in Chlorophyll-a, Carotenoids, CDOM and SO₄(2-) Intensity of Offshore Seawater Detected by an Underwater Fluorescence-Raman Spectral System.

Science.gov (United States)

Chen, Jing; Ye, Wangquan; Guo, Jinjia; Luo, Zhao; Li, Ying

2016-07-13

A newly developed integrated fluorescence-Raman spectral system (λex = 532 nm) for detecting Chlorophyll-a (chl-a), Chromophoric Dissolved Organic Matter (CDOM), carotenoids and SO₄(2-) in situ was used to successfully investigate the diurnal variability of all above. Simultaneously using the integration of fluorescence spectroscopy and Raman spectroscopy techniques provided comprehensive marine information due to the complementarity between the different excitation mechanisms and different selection rules. The investigation took place in offshore seawater of the Yellow Sea (36°05'40'' N, 120°31'32'' E) in October 2014. To detect chl-a, CDOM, carotenoids and SO₄(2-), the fluorescence-Raman spectral system was deployed. It was found that troughs of chl-a and CDOM fluorescence signal intensity were observed during high tides, while the signal intensity showed high values with larger fluctuations during ebb-tide. Chl-a and carotenoids were influenced by solar radiation within a day cycle by different detection techniques, as well as displaying similar and synchronous tendency. CDOM fluorescence cause interference to the measurement of SO₄(2-). To avoid such interference, the backup Raman spectroscopy system with λex = 785 nm was employed to detect SO₄(2-) concentration on the following day. The results demonstrated that the fluorescence-Raman spectral system has great potential in detection of chl-a, carotenoids, CDOM and SO₄(2-) in the ocean.

On-off QD switch that memorizes past recovery from quenching by diazonium salts.

Science.gov (United States)

Liras, Marta; González-Béjar, María; Scaiano, J C

2010-09-07

The understanding of the interaction of CdSe/ZnS semiconductor quantum dots (QD) with their chemical environment is fundamental, yet far from being fully understood. p-Methylphenyldiazonium tetrafluoroborate has been used to get some insight into the effect of diazonium salts on the spectroscopy of QD. Our study reveals that the surface of CdSe/ZnS quantum dots can be modified by diazonium salts (although not functionalized), showing and on-off fluorescence behaviour that memorizes past quenching recoveries. Facile modification of the surface confers protection against quenching by new molecules of diazonium salt and other known quenchers such as 4-amino-TEMPO. The reaction mechanism has been explored in detail by using different spectroscopic techniques. At the first time after addition of diazonium salt over QD the fluorescent is turned off with Stern-Volmer behaviour; the fluorescence recovers following irradiation. Subsequent additions of diazonium salts do not cause the same degree of quenching. We have noted that the third addition (following two cycles of addition and irradiation) is unable to quench the fluorescence. Monitoring the process using NMR techniques reveals the formation of p-difluoroborane toluene as a result of the irradiation of diazonium-treated QD; the treatment leads to the fluorination of the QD surface.

Synergistic Combination of Unquenching and Plasmonic Fluorescence Enhancement in Fluorogenic Nucleic Acid Hybridization Probes.

Science.gov (United States)

Vietz, Carolin; Lalkens, Birka; Acuna, Guillermo P; Tinnefeld, Philip

2017-10-11

Fluorogenic nucleic acid hybridization probes are widely used for detecting and quantifying nucleic acids. The achieved sensitivity strongly depends on the contrast between a quenched closed form and an unquenched opened form with liberated fluorescence. So far, this contrast was improved by improving the quenching efficiency of the closed form. In this study, we modularly combine these probes with optical antennas used for plasmonic fluorescence enhancement and study the effect of the nanophotonic structure on the fluorescence of the quenched and the opened form. As quenched fluorescent dyes are usually enhanced more by fluorescence enhancement, a detrimental reduction of the contrast between closed and opened form was anticipated. In contrast, we could achieve a surprising increase of the contrast with full additivity of quenching of the dark form and fluorescence enhancement of the bright form. Using single-molecule experiments, we demonstrate that the additivity of the two mechanisms depends on the perfect quenching in the quenched form, and we delineate the rules for new nucleic acid probes for enhanced contrast and absolute brightness. Fluorogenic hybridization probes optimized not only for quenching but also for the brightness of the open form might find application in nucleic acid assays with PCR avoiding detection schemes.

Portable plant chlorophyll fluorimeter based on blue LED rapid induced technology

Science.gov (United States)

Zheng, Yibo; Mi, Ting; Zhang, Lei; Zhao, Jun

2018-01-01

Fluorimeter is an effective device for detecting chlorophyll a content in plants. In order to realize real-time nondestructive detection of plant blades, a camera based fluorescence instrument based on two color mirrors has been developed. The blue light LED is used as the excitation light source, and the lens is used for shaping and focusing the excitation light to ensure the excitation intensity and uniform illumination of the light source. The device uses a 45 degree two color mirror to separate the chlorophyll a excited light path and the fluorescence receiving light path. Finally, the fluorescent signal is collected by the silicon photocell, and the signal is processed by the circuit to transmit the digital information to the display. Through the analysis of the experimental data, the device has the advantages of small size, easy to carry, fast induction, etc., and can be widely applied in outdoor teaching and field investigation.

Quenching mechanism of exciplex fluorescence by inverted micelles

International Nuclear Information System (INIS)

Sato, Chika; Kikuchi, Koichi

1992-01-01

Using an emission-absorption laser photolysis method, the quenching mechanism of the pyrene-N,N-dimethylaniline exciplex fluorscence by inverted micelles is studied. The rate of enhanced intersystem crossing depends upon water pool size and is reduced by external magnetic fields. 15 refs., 3 figs., 2 tabs

Assessing boreal forest photosynthetic dynamics through space-borne measurements of greenness, chlorophyll fluorescence and model GPP

Science.gov (United States)

Walther, Sophia; Guanter, Luis; Voigt, Maximilian; Köhler, Philipp; Jung, Martin; Joiner, Joanna

2015-04-01

sophia.walther@gfz-potsdam.de The seasonality of photosynthesis of boreal forests is an essential driver of the terrestrial carbon, water and energy cycles. However, current carbon cycle model results only poorly represent interannual variability and predict very different magnitudes and timings of carbon fluxes between the atmosphere and the land surface (e.g. Jung et al. 2011, Richardson et al. 2012). Reflectance-based satellite measurements, which give an indication of the amount of green biomass on the Earth's surface, have so far been used as input to global carbon cycle simulations, but they have limitations as they are not directly linked to instantaneous photosynthesis. As an alternative, space-borne retrievals of sun-induced chlorophyll fluorescence (SIF) boast the potential to provide a direct indication of the seasonality of boreal forest photosynthetic activity and thus to improve carbon model performances. SIF is a small electromagnetic signal that is re-emitted from the photosystems in the chloroplasts, which results in a direct relationship to photosynthetic efficiency. In this contribution we examine the seasonality of the boreal forests with three different vegetation parameters, namely greenness, SIF and model simulations of gross primary production (gross carbon flux into the plants by photosynthesis, GPP). We use the enhanced vegetation index (EVI) to represent green biomass. EVI is calculated from NBAR MODIS reflectance measurements (0.05deg, 16 days temporal resolution) for the time from January 2007-May 2013. SIF data originate from GOME-2 measurements on board the MetOp-A satellite in a spatial resolution of 0.5deg for the time from 2007-2011 (Joiner et al. (2013), Köhler et al. (2014)). As a third data source, data-driven GPP model results are used for the time from 2006-2012 with 0.5deg spatial resolution. The method to quantify phenology developed by Gonsamo et al. (2013) is applied to infer the main phenological phases (greenup/onset of

[Quenched fluorescein: a reference dye for instrument response function of TCSPC].

Science.gov (United States)

Pan, Hai-feng; Ding, Jing-xin; Liang, Rong-rong; Tao, Zhan-dong; Liu, Meng-wei; Zhang, San-jun; Xu, Jian-hua

2014-08-01

Measuring the instrument response function (IRF) and fitting by reconvolution algorithms are routines to improve time resolution in fluorescence lifetime measurements. Iodide ions were successfully used to quench the fluorescence of fluorescein in this study. By systematically adding saturated NaI water solution in basic fluorescein solution, the lifetimes of fluorescein were reduced from 4 ns to 24 ps. The quenched lifetime of fluorescein obtained from the analysis of Time-Correlated Single Photon Counting (TCSPC) measurement agrees well with that from femtosecond frequency up-conversion measurement. In time resolved excitation spectra measurements, the IRF should be measured at various detection wavelengths providing scattring materials are used. This study could not only reduce the complexity of IRF measurement, but also avoid the existing color effect in system. This study should have wide applications in time resolved fluorescence spectroscopy and fluorescence lifetime imaging.

Stress tolerance and stress-induced injury in crop plants measured by chlorophyll fluorescence in vivo: chilling, freezing, ice cover, heat, and high light.

Science.gov (United States)

Smillie, R M; Hetherington, S E

1983-08-01

The proposition is examined that measurements of chlorophyll fluorescence in vivo can be used to monitor cellular injury caused by environmental stresses rapidly and nondestructively and to determine the relative stress tolerances of different species. Stress responses of leaf tissue were measured by F(R), the maximal rate of the induced rise in chlorophyll fluorescence. The time taken for F(R) to decrease by 50% in leaves at 0 degrees C was used as a measure of chilling tolerance. This value was 4.3 hours for chilling-sensitive cucumber. In contrast, F(R) decreased very slowly in cucumber leaves at 10 degrees C or in chilling-tolerant cabbage leaves at 0 degrees C. Long-term changes in F(R) of barley, wheat, and rye leaves kept at 0 degrees C were different in frost-hardened and unhardened material and in the latter appeared to be correlated to plant frost tolerance. To simulate damage caused by a thick ice cover, wheat leaves were placed at 0 degrees C under N(2). Kharkov wheat, a variety tolerant of ice encapsulation, showed a slower decrease in F(R) than Gatcher, a spring wheat. Relative heat tolerance was also indicated by the decrease in F(R) in heated leaves while changes in vivo resulting from photoinhibition, ultraviolet radiation, and photobleaching can also be measured.

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;

Spinach seed quality - potential for combining seed size grading and chlorophyll flourescence sorting

DEFF Research Database (Denmark)

Deleuran, Lise Christina; Olesen, Merete Halkjær; Boelt, Birte

2013-01-01

might therefore improve the establishment of spinach for producers. Spinach seeds were harvested at five different times (H1, H2, H3, H4 and H5) starting 3 weeks before estimated optimum harvest time. The harvested seeds were sorted according to chlorophyll fluorescence (CF) and seed size. Two harvest.......5–3.25 mm size seeds had germinated on day 3 than both their larger and smaller counterparts at the later time of harvest (H4). Seeds with a diameter below 2.5 mm displayed the lowest MGT. Commercially, the use of chlorophyll fluorescence (CF)-sorted seeds, in combination with seed size sorting, may provide...

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

Homogeneous non-competitive bioaffinity assay based on fluorescence resonance energy transfer

International Nuclear Information System (INIS)

Kokko, Tiina; Kokko, Leena; Soukka, Tero; Loevgren, Timo

2007-01-01

A homogeneous non-competitive assay principle for measurement of small analytes based on quenching of fluorescence is described. Fluorescence resonance energy transfer (FRET) occurs between the donor, intrinsically fluorescent europium(III)-chelate conjugated to streptavidin, and the acceptor, quencher dye conjugated to biotin derivative when the biotin-quencher is bound to Eu-streptavidin. Fluorescence can be measured only from those streptavidins that are bound to biotin of the sample, while the fluorescence of the streptavidins that are not occupied by biotin are quenched by quencher-biotin conjugates. The quenching efficiencies of the non-fluorescent quencher dyes were over 95% and one dye molecule was able to quench the fluorescence of more than one europium(III)-chelate. This, however, together with the quadrovalent nature of streptavidin limited the measurable range of the assay to 0.2-2 nmol L -1 . In this study we demonstrated that FRET could be used to design a non-competitive homogeneous assay for a small analyte resulting in equal performance with competitive heterogeneous assay

Relation of Chlorophyll Fluorescence Sensitive Reflectance Ratios to Carbon FluxMeasurements ofMontanne Grassland and Norway Spruce Forest Ecosystems in the Temperate Zone

Czech Academy of Sciences Publication Activity Database

Ač, Alexander; Malenovský, Z.; Urban, Otmar; Hanuš, Jan; Zitová, Martina; Navrátil, M.; Vráblová, M.; Olejníčková, Julie; Špunda, V.; Marek, Michal V.

2012-01-01

Roč. 2012, č. 2012 (2012), s. 1-13 ISSN 1537-744X R&D Projects: GA MŽP(CZ) SP/2D1/70/08; GA MŽP(CZ) SP/2D1/93/07; GA MŠk(CZ) LM2010007; GA MŠk(CZ) ED1.1.00/02.0073 Institutional research plan: CEZ:AV0Z60870520 Keywords : Chlorophyll fluorescence * carbon flux * forest ecosystems * Norway Spruce * temperate zone Subject RIV: EH - Ecology, Behaviour Impact factor: 1.730, year: 2012

Fluorescence of Alexa fluor dye tracks protein folding.

Directory of Open Access Journals (Sweden)

Simon Lindhoud

Full Text Available Fluorescence spectroscopy is an important tool for the characterization of protein folding. Often, a protein is labeled with appropriate fluorescent donor and acceptor probes and folding-induced changes in Förster Resonance Energy Transfer (FRET are monitored. However, conformational changes of the protein potentially affect fluorescence properties of both probes, thereby profoundly complicating interpretation of FRET data. In this study, we assess the effects protein folding has on fluorescence properties of Alexa Fluor 488 (A488, which is commonly used as FRET donor. Here, A488 is covalently attached to Cys69 of apoflavodoxin from Azotobacter vinelandii. Although coupling of A488 slightly destabilizes apoflavodoxin, the three-state folding of this protein, which involves a molten globule intermediate, is unaffected. Upon folding of apoflavodoxin, fluorescence emission intensity of A488 changes significantly. To illuminate the molecular sources of this alteration, we applied steady state and time-resolved fluorescence techniques. The results obtained show that tryptophans cause folding-induced changes in quenching of Alexa dye. Compared to unfolded protein, static quenching of A488 is increased in the molten globule. Upon populating the native state both static and dynamic quenching of A488 decrease considerably. We show that fluorescence quenching of Alexa Fluor dyes is a sensitive reporter of conformational changes during protein folding.

Polyethylenimine-coated Fe3O4 nanoparticles effectively quench fluorescent DNA, which can be developed as a novel platform for protein detection.

Science.gov (United States)

Ma, Long; Sun, Nana; Zhang, Jinyan; Tu, Chunhao; Cao, Xiuqi; Duan, Demin; Diao, Aipo; Man, Shuli

2017-11-23

We report a novel assembly of polyethyleneimine (PEI)-coated Fe 3 O 4 nanoparticles (NPs) with single-stranded DNA (ssDNA), and the fluorescence of the dye labeled in the DNA is remarkably quenched. In the presence of a target protein, the protein-DNA aptamer mutual interaction releases the ssDNA from this assembly and hence restores the fluorescence. This feature could be adopted to develop an aptasensor for protein detection. As a proof-of-concept, for the first time, we have used this proposed sensing strategy to detect thrombin selectively and sensitively. Furthermore, simultaneous multiple detection of thrombin and lysozyme in a complex protein mixture has been proven to be possible.

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;

Sensitive determination of enoxacin in pharmaceutical formulations by its quench effect on the fluorescence of glutathione-capped CdTe quantum dots.

Science.gov (United States)

Yang, Qiong; Tan, Xuanping; Yang, Jidong

2016-02-01

A sensitive and simple method for the determination of enoxacin (ENX) was developed based on the fluorescence quenching effect of ENX for glutathione (GSH)-capped CdTe quantum dots (QDs). Under optimum conditions, a good linear relationship was obtained from 4.333 × 10(-9)  mol⋅L(-1) to 1.4 × 10(-5)  mol⋅L(-1) with a correlation coefficient (R) of 0.9987, and the detection limit (3σ/K) was 1.313 × 10(-9)  mol⋅L(-1). The corresponding mechanism has been proposed on the basis of electron transfer supported by ultraviolet-visible (UV) light absorption, fluorescence spectroscopy, and the measurement of fluorescence lifetime. The method has been applied to the determination of ENX in pharmaceutical formulations (enoxacin gluconate injections and commercial tablets) with satisfactory results. The proposed method manifested several advantages such as high sensitivity, short analysis time, low cost and ease of operation. Copyright © 2015 John Wiley & Sons, Ltd.

The Validity Chlorophyll-a Estimation by Sun Induced Fluorescence in Estuarine Waters: An Analysis of Long-term (2003-2011) Water Quality Data from Tampa Bay, Florida (USA)

Science.gov (United States)

Moreno-Madrinan, Max Jacobo; Fischer, Andrew

2012-01-01

Satellite observation of phytoplankton concentration or chlorophyll-a is an important characteristic, critically integral to monitoring coastal water quality. However, the optical properties of estuarine and coastal waters are highly variable and complex and pose a great challenge for accurate analysis. Constituents such as suspended solids and dissolved organic matter and the overlapping and uncorrelated absorptions in the blue region of the spectrum renders the blue-green ratio algorithms for estimating chlorophyll-a inaccurate. Measurement of sun-induced chlorophyll fluorescence, on the other hand, which utilizes the near infrared portion of the electromagnetic spectrum, may provide a better estimate of phytoplankton concentrations. While modelling and laboratory studies have illustrated both the utility and limitations of satellite baseline algorithms based on the sun induced chlorophyll fluorescence signal, few have examined the empirical validity of these algorithms using a comprehensive long term in situ data set. In an unprecedented analysis of a long term (2003-2011) in situ monitoring data from Tampa Bay, Florida (USA), we assess the validity of the FLH product from the Moderate Resolution Imaging Spectrometer (MODIS) against chlorophyll ]a and a suite of water quality parameters taken in a variety of conditions throughout a large optically complex estuarine system. A systematic analysis of sampling sites throughout the bay is undertaken to understand how the relationship between FLH and in situ chlorophyll-a responds to varying conditions within the estuary including water depth, distance from shore and structures and eight water quality parameters. From the 39 station for which data was derived, 22 stations showed significant correlations when the FLH product was matched with in situ chlorophyll-alpha data. The correlations (r2) for individual stations within Tampa Bay ranged between 0.67 (n=28, pless than 0.01) and-0.457 (n=12, p=.016), indicating that

Hydroxymethylated Dioxobilins in Senescent Arabidopsis thaliana Leaves: Sign of a Puzzling Biosynthetic Intermezzo of Chlorophyll Breakdown.

Science.gov (United States)

Süssenbacher, Iris; Kreutz, Christoph R; Christ, Bastien; Hörtensteiner, Stefan; Kräutler, Bernhard

2015-08-10

1-Formyl-19-oxobilin-type tetrapyrroles are characteristic, abundant products of chlorophyll breakdown in senescent leaves. However, in some leaves, 1,19-dioxobilin-type chlorophyll catabolites (DCCs) lacking the formyl group accumulate instead. A P450 enzyme was identified in in vitro studies that removed the formyl group of a primary fluorescent chlorophyll catabolite (pFCC) and generated fluorescent DCCs. These DCCs are precursors of isomeric nonfluorescent DCCs (NDCCs). Here, we report a structural investigation of the NDCCs in senescent leaves of wild-type Arabidopsis thaliana. Four new NDCCs were characterized, two of which carried a stereoselectively added hydroxymethyl group. Such formal DCC hydroxymethylations were previously found in DCCs in leaves of a mutant of A. thaliana. They are now indicated to be a feature of chlorophyll breakdown in A. thaliana, associated with the specific in vivo deformylation of pFCC en route to NDCCs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Correlation between Strawberry (Fragaria ananassa Duch. Productivity and Photosynthesis-related Parameters under Various Growth Conditions

Directory of Open Access Journals (Sweden)

Hyo Gil Choi

2016-10-01

Full Text Available In the present study, we investigated changes in chlorophyll fluorescence, photosynthetic parameters and fruit yields, as well as fruit phytochemical accumulation of strawberry (Fragaria ananassa Duch. that had been cultivated in a greenhouse under different combinations of light intensity and temperature. In plants grown with low light (LL photosystem II chlorophyll fluorescence was found to increase as compared with those grown under high light (HL. When strawberry plants were grown with temperature higher than 5◦C in addition to LL, they showed decrease in non-photochemical quenching (NPQ, photochemical quenching (qP, as well as chlorophyll fluorescence decrease ratio (RFd when compared with other combinations of light and temperature. Moreover, fruit yield of strawberry was closely correlated with chlorophyll fluorescence-related parameters such as NPQ, qP, and RFd, but not with the maximum efficiency of PS II (Fv/Fm. Although plant groups grown under different combinations of light and temperature showed almost comparable levels of photosynthesis rates (Pr when irradiated with low-intensity light, they displayed clear differences when measured with higher irradiances. Plants grown under HL with temperature above 10◦C showed the highest Pr, in contrast to the plants grown under LL with temperature above 5◦C. When the stomatal conductance and the transpiration rate were measured, plants of each treatment showed clear differences even when analyzed with lower irradiances. We also found that fruit production during winter season was more strongly influenced by growth temperature than light intensity. We suggest that fruit productivity of strawberry is closely associated with chlorophyll fluorescence and photosynthesis-related parameters during cultivation under different regimes of temperature and light.

Fluorescence enhancement and quenching of Eu(TTFA)3 by Ag nanoparticles at different excitations

International Nuclear Information System (INIS)

Wang, Qingru; Shi, Qiang; Li, Shuhong; Wang, Wenjun; Zheng, Shiling

2015-01-01

The luminescence properties of Eu(TTFA) 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

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)

Wu, Huanyang

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.

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.

Delayed chlorophyll a fluorescence, MR 820, and gas exchange changes in perennial ryegrass under salt stress

Energy Technology Data Exchange (ETDEWEB)

Dąbrowski, P., E-mail: piotr_dabrowski@sggw.pl [Department of Environmental Improvement, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); Kalaji, M.H., E-mail: hazem@kalaji.pl [Department of Plant Physiology, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); SI TECHNOLOGY Sp. z o. o., Górczewska 226C/26, 01-460 Warsaw (Poland); Baczewska, A.H., E-mail: a.baczewska@obpan.pl [Polish Academy of Sciences Botanical Garden-Center for Biological Diversity Conservation in Powsin, 2 Prawdziwka St., 02-973 Warsaw (Poland); Pawluśkiewicz, B. [Department of Environmental Improvement, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); Mastalerczuk, G., E-mail: grazyna_mastalerczuk@sggw.pl [Department of Agronomy, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); Borawska-Jarmułowicz, B., E-mail: barbara_borawska_jarmulowicz@sggw.pl [Department of Agronomy, Warsaw University of Life Sciences-SGGW, 159 Nowoursynowska St., 02-776 Warsaw (Poland); Paunov, M. [Department Biophysics and Radiobiology, St. Kl. Ohridski Sofia University, 8 Dragan Tsankov Blvd., 1164 Sofia (Bulgaria); Goltsev, V., E-mail: goltsev@biofac.uni-sofia.bg [Department Biophysics and Radiobiology, St. Kl. Ohridski Sofia University, 8 Dragan Tsankov Blvd., 1164 Sofia (Bulgaria)

2017-03-15

Perennial ryegrass (Lolium perenne L.) is one of the more popular grass species in Europe. It is commonly used for starting lawns in urban areas, where plant growth is limited by many environmental conditions. The contamination of soils by salt is one of the major problems in urban green areas, as well as in natural areas. The basic aim of this study is to provide a detailed in vivo analysis of the changes in the delayed chlorophyll fluorescence and MR 820 signals (induced by salt stress) of two lawn varieties of perennial ryegrass, and to find out if there are correlations between these parameters and gas exchange. Two lawn varieties of Lolium perenne L. were used: Nira and Roadrunner. Salinization was performed at 8 weeks after sowing by adding NaCl in water solution (0, 0.15, and 0.30 M). There were 8 terms of measurement: 0 h, 24 h, 48 h, 96 h, 144 h, 192 h, 240 h, and 288 h after salinization. Our results showed that delayed fluorescence is a tool that can bring completely new opportunities for detecting stress in plants caused by salt. Our work allowed us to identify various limitation patterns in the photosynthetic efficiency of perennial ryegrass lawn varieties grown under salt stress conditions. Significant differences between the two tested varieties in response to salt stress were confirmed.

Impact of 3D Canopy Structure on Remote Sensing Vegetation Index and Solar Induced Chlorophyll Fluorescence

Science.gov (United States)

Zeng, Y.; Berry, J. A.; Jing, L.; Qinhuo, L.

2017-12-01

Terrestrial ecosystem plays a critical role in removing CO2 from atmosphere by photosynthesis. Remote sensing provides a possible way to monitor the Gross Primary Production (GPP) at the global scale. Vegetation Indices (VI), e.g., NDVI and NIRv, and Solar Induced Fluorescence (SIF) have been widely used as a proxy for GPP, while the impact of 3D canopy structure on VI and SIF has not be comprehensively studied yet. In this research, firstly, a unified radiative transfer model for visible/near-infrared reflectance and solar induced chlorophyll fluorescence has been developed based on recollision probability and directional escape probability. Then, the impact of view angles, solar angles, weather conditions, leaf area index, and multi-layer leaf angle distribution (LAD) on VI and SIF has been studied. Results suggest that canopy structure plays a critical role in distorting pixel-scale remote sensing signal from leaf-scale scattering. In thin canopy, LAD affects both of the remote sensing estimated GPP and real GPP, while in dense canopy, SIF variations are mainly due to canopy structure, instead of just due to physiology. At the microscale, leaf angle reflects the plant strategy to light on the photosynthesis efficiency, and at the macroscale, a priori knowledge of leaf angle distribution for specific species can improve the global GPP estimation by remote sensing.

Delayed chlorophyll a fluorescence, MR 820, and gas exchange changes in perennial ryegrass under salt stress

International Nuclear Information System (INIS)

Dąbrowski, P.; Kalaji, M.H.; Baczewska, A.H.; Pawluśkiewicz, B.; Mastalerczuk, G.; Borawska-Jarmułowicz, B.; Paunov, M.; Goltsev, V.

2017-01-01

Perennial ryegrass (Lolium perenne L.) is one of the more popular grass species in Europe. It is commonly used for starting lawns in urban areas, where plant growth is limited by many environmental conditions. The contamination of soils by salt is one of the major problems in urban green areas, as well as in natural areas. The basic aim of this study is to provide a detailed in vivo analysis of the changes in the delayed chlorophyll fluorescence and MR 820 signals (induced by salt stress) of two lawn varieties of perennial ryegrass, and to find out if there are correlations between these parameters and gas exchange. Two lawn varieties of Lolium perenne L. were used: Nira and Roadrunner. Salinization was performed at 8 weeks after sowing by adding NaCl in water solution (0, 0.15, and 0.30 M). There were 8 terms of measurement: 0 h, 24 h, 48 h, 96 h, 144 h, 192 h, 240 h, and 288 h after salinization. Our results showed that delayed fluorescence is a tool that can bring completely new opportunities for detecting stress in plants caused by salt. Our work allowed us to identify various limitation patterns in the photosynthetic efficiency of perennial ryegrass lawn varieties grown under salt stress conditions. Significant differences between the two tested varieties in response to salt stress were confirmed.

Quenching-induced deactivation of photosensitizer by nanoencapsulation to improve phototherapy of cancer.

Science.gov (United States)

Zeisser-Labouèbe, Magali; Mattiuzzo, Marc; Lange, Norbert; Gurny, Robert; Delie, Florence

2009-09-01

Photodynamic therapy has emerged as a promising alternative to current cancer treatment. However, conventional photosensitizers have several limitations due to their unsuitable pharmaceutical formulations and lack of selectivity. Our strategy was to exploit the advantages of nanoparticles and the quenching-induced deactivation of the model photosensitizer hypericin to produce "activatable" drug delivery systems. Efficient fluorescence and activity quenching were achieved by increasing the drug-loading rate of nanoparticles. In vitro assays confirmed the reversibility of hypericin deactivation, as the hypericin fluorescence and photodynamic activity were recovered upon cell internalization.

NeutrAvidin Functionalization of CdSe/CdS Quantum Nanorods and Quantification of Biotin Binding Sites using Biotin-4-Fluorescein Fluorescence Quenching

OpenAIRE

Lippert, Lisa G.; Hallock, Jeffrey T.; Dadosh, Tali; Diroll, Benjamin T.; Murray, Christopher B.; Goldman, Yale E.

2016-01-01

We developed methods to solubilize, coat, and functionalize with NeutrAvidin elongated semiconductor nanocrystals (quantum nanorods, QRs) for use in single molecule polarized fluorescence microscopy. Three different ligands were compared with regard to efficacy for attaching NeutrAvidin using the “zero-length cross-linker” 1-ethyl-3-[3-(dimethylamino)propyl]-carbodiimide (EDC). Biotin-4-fluorescene (B4F), a fluorophore that is quenched when bound to avidin proteins, was used to quantify bioti...

Probe for intracellular concentrations of drugs: delayed fluorescence from acridine orange

International Nuclear Information System (INIS)

Wardman, P.; Dennis, M.F.; White, J.

1989-01-01

The aim of this work is to develop fluorescent probes that will indicate effective concentrations of therapeutic agents, or endogenous protectors, at important cellular sites. Acridine orange associates with nucleic acids and emits a 'delayed' fluorescence signal. This signal is quenched by oxidants such as oxygen, nitroaryl radiosensitizers, adriamycin and mitomycin-c, and reductants such as thiols, ascorbate and other radioprotectors. The quenching of the acridine orange delayed fluorescence reflects the effective concentration of these therapeutically-important oxidants and reductants near DNA. The relative concentration of basic radiosensitizers such as pimonidazole (Ro 03-8799) near the DNA is greater than that of misonidazole. Thiols quench the delayed fluorescence signal according to the degree of ionization of the thiol function; this may model the reactivity of thiols with guanine radical sites in DNA. Ascorbate and aminopyrine do not quench the delayed fluorescence from cells stained with acridine orange as these compounds are taken up by cells very inefficiently

Evaluation of diatomea algae Thalassiosira weissflogii sensitivity to chloride mercury and methylmercury by chlorophyll fluorescence analysis

Science.gov (United States)

Graevskaya, E. E.; Antal, T. K.; Matorin, D. N.; Voronova, E. N.; Pogosyan, S. I.; Rubin, A. B.

2003-05-01

Measurement of chlorophyll fluorescence has been shown to be a rapid, non-invasive, and reliable method to assess photosynthetic performance in a changing environment. In our study, the pulseamplitude-modulation (PAM) - fluorometric method was used to evaluate the sensitivity to chloride mercury and methylmercury chloride of diatomea microalgae Thalassiosira weissflogii. We found that 10^{-6} and 10^{-7} M MeHg led to a slow decrease in the PS II activity following for prolonged lag phase, whereas the algae was not sensitive to the same concentrations of HgCl2. However observed PS II inactivation by methylmercury was not complete and about 10 percents ofthe cells kept the high level of PS II activity as it was shown by microfluorometric analysis. These cells could determine adaptation of algae to methylmercury effect. Both toxicants decreased the rate of PS II reparation, as well as increased a heat pathway of excitation dissipation in PS II antennae complex.

Fluorescence properties of 3-amino phenylboronic acid and its interaction with glucose and ZnS:Cu quantum dots.

Science.gov (United States)

Kur-Kowalska, Karolina; Przybyt, Małgorzata; Ziółczyk, Paulina; Sowiński, Przemysław; Miller, Ewa

2014-08-14

Preliminary results of a study of the interaction between 3-amino phenylboronic acid and glucose or ZnS:Cu quantum dots are presented in this paper. ZnS:Cu quantum dots with mercaptopropionic acid as a capping agent were obtained and characterized. Quenching of 3-amino phenylboronic acid fluorescence was studied by steady-state and timeresolved measurements. For fluorescence quenching with glucose the results of steady-state measurements fulfill Stern-Volmer equation. The quenching constants are increasing with growing pH. The decay of fluorescence is monoexponential with lifetime about 8.4 ns, which does not depend on pH and glucose concentration indicating static quenching. The quenching constant can be interpreted as apparent equilibrium constant of estrification of boronic group with diol. Quantum dots are also quenching 3-amino phenylboronic acid fluorescence. Fluorescence lifetime, in this case, is slightly decreasing with increasing concentration of quantum dots. The quenching constants are increasing slightly with pH's growth. Quenching mechanism of 3-amino phenylboronic acid fluorescence by quantum dots needs further experiments to be fully explained. Copyright © 2014 Elsevier B.V. All rights reserved.

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.;

Chlorophyll as a biomarker for early disease diagnosis

Science.gov (United States)

Manzoor Atta, Babar; Saleem, M.; Ali, Hina; Arshad, Hafiz Muhammad Imran; Ahmed, M.

2018-06-01

The current study was designed to identify the stage for the diagnosis of disease before visible symptoms appeared. Fluorescence spectroscopy has been employed to identify disease signatures for its early diagnosis in rice plant leaves. Bacterial leaf blight (BLB) diseased and healthy leaf samples were collected from the rice fields in September, 2017 which were then used to record spectra using an excitation wavelength at 410 nm. The spectral range of emission was set from 420 to 800 nm which covers the blue–green and the chlorophyll bands. It was found that diseased leaves have a narrower ‘chlorophyll a’ band than healthy ones, and furthermore, that the emission band at 730 nm was either declined or depleted in the sample with high infection symptoms. In contrast, the blue–green region was observed to increase due to the emergence of disease. As the band intensity of chlorophyll decreases during infection, this decrease in chlorophyll content and increase in the blue–green spectral region could provide a new approach for predicting BLB at an early stage. The important finding was that the chlorophyll degradation and rise in the blue–green region take place in leaves with BLB or during BLB infection. Principal component analysis has been applied to spectral data which successfully separated diseased samples from healthy ones even with very small spectral variations.

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

Modern highly insulated greenhouses are more energy efficient than conventional types. Furthermore applying dynamic greenhouse climate control regimes will increase energy efficiency relatively more in modern structures. However, this combination may result in higher air and crop temperatures. Too...... high temperature affects the plant photosynthetic responses, resulting in a lower rate of photosynthesis. To predict and analyse physiological responses as stress indicators, two independent experiments were conducted, to detect the effect of high temperature on photosynthesis: analysing photosystem II...... (PSII) and stomatal conductance (gs). A combination of chlorophyll a fluorescence, gas exchange measurements and infrared thermography was applied using Chrysanthemum (Dendranthema grandiflora Tzvelev) ‘Coral Charm’ as a model species. Increasing temperature had a highly significant effect on PSII when...

Luminescence quenching by heavy metal ions of probes based on anthracene, pyrene, and eosin in human serum albumin

Science.gov (United States)

Naumova, E. V.; Melnikov, A. G.; Melnikov, G. V.

2013-05-01

Fluorescence and phosphorescence quenching processes of polar and non-polar luminescent probes associated with human serum albumin (HSA) in phosphate buffer at pH 7.4 were studied. Stern-Volmer quenching constants of anthracene and pyrene fluorescence and eosin phosphorescence and rate constants for quenching of eosin triplet states were determined. The polarity index of pyrene bound to HSA was obtained as a function of thallium nitrate concentration. The influences of structural changes in the proteins that were stimulated by heavy-metal salts and of screening of protein charges by salt ions on quenching processes of singlet and triplet states of the probes were found.

Suppression of non-photochemical quenching in Arabidopsis leaves to a ionizing radiation

International Nuclear Information System (INIS)

Yu Ran Moon; Jin-Hong Kim; Min Hee Lee; Byung Yeoup Chung; Jae-Sung Kim

2007-01-01

Complete text of publication follows. Non-photochemical quenching (NPQ) of chlorophyll fluorescence has been known to be involved in a protection of photosystems against photoinhibition through a dissipation of excess light absorbed by photosynthetic pigments. In the present study, we aimed to elucidate the effects of a ionizing radiation on NPQ by comparing alterations in the development and release of NPQ after gamma-irradiation between the wild-type (WT) and the npq1-2 mutant of Arabidopsis. The npq1-2 mutant can't develop with a normal NPQ under excess light, since it is defective in its de-epoxidase activity for conversion of violaxanthin to zeaxanthin. Gamma-irradiation with a dose of 200 Gy inhibited the development of NPQ in both the WT and mutant but more noticeably in the latter. Moreover, Fv/Fm as an indice of the photochemical efficiency of photosystem II (PSII) was almost the same in both the WT and npq1-2 mutant throughout the post-irradiation period of 5 d. The obtained results will be also discussed with those from photoinhibition induced by non-ionizing radiations such as visible light and UV-B.

Diurnal Variability in Chlorophyll-a, Carotenoids, CDOM and SO42− Intensity of Offshore Seawater Detected by an Underwater Fluorescence-Raman Spectral System

Science.gov (United States)

Chen, Jing; Ye, Wangquan; Guo, Jinjia; Luo, Zhao; Li, Ying

2016-01-01

A newly developed integrated fluorescence-Raman spectral system (λex = 532 nm) for detecting Chlorophyll-a (chl-a), Chromophoric Dissolved Organic Matter (CDOM), carotenoids and SO42− in situ was used to successfully investigate the diurnal variability of all above. Simultaneously using the integration of fluorescence spectroscopy and Raman spectroscopy techniques provided comprehensive marine information due to the complementarity between the different excitation mechanisms and different selection rules. The investigation took place in offshore seawater of the Yellow Sea (36°05′40′′ N, 120°31′32′′ E) in October 2014. To detect chl-a, CDOM, carotenoids and SO42−, the fluorescence-Raman spectral system was deployed. It was found that troughs of chl-a and CDOM fluorescence signal intensity were observed during high tides, while the signal intensity showed high values with larger fluctuations during ebb-tide. Chl-a and carotenoids were influenced by solar radiation within a day cycle by different detection techniques, as well as displaying similar and synchronous tendency. CDOM fluorescence cause interference to the measurement of SO42−. To avoid such interference, the backup Raman spectroscopy system with λex = 785 nm was employed to detect SO42− concentration on the following day. The results demonstrated that the fluorescence-Raman spectral system has great potential in detection of chl-a, carotenoids, CDOM and SO42− in the ocean. PMID:27420071

Diurnal Variability in Chlorophyll-a, Carotenoids, CDOM and SO42− Intensity of Offshore Seawater Detected by an Underwater Fluorescence-Raman Spectral System

Directory of Open Access Journals (Sweden)

Jing Chen

2016-07-01

Full Text Available A newly developed integrated fluorescence-Raman spectral system (λex = 532 nm for detecting Chlorophyll-a (chl-a, Chromophoric Dissolved Organic Matter (CDOM, carotenoids and SO42− in situ was used to successfully investigate the diurnal variability of all above. Simultaneously using the integration of fluorescence spectroscopy and Raman spectroscopy techniques provided comprehensive marine information due to the complementarity between the different excitation mechanisms and different selection rules. The investigation took place in offshore seawater of the Yellow Sea (36°05′40′′ N, 120°31′32′′ E in October 2014. To detect chl-a, CDOM, carotenoids and SO42−, the fluorescence-Raman spectral system was deployed. It was found that troughs of chl-a and CDOM fluorescence signal intensity were observed during high tides, while the signal intensity showed high values with larger fluctuations during ebb-tide. Chl-a and carotenoids were influenced by solar radiation within a day cycle by different detection techniques, as well as displaying similar and synchronous tendency. CDOM fluorescence cause interference to the measurement of SO42−. To avoid such interference, the backup Raman spectroscopy system with λex = 785 nm was employed to detect SO42− concentration on the following day. The results demonstrated that the fluorescence-Raman spectral system has great potential in detection of chl-a, carotenoids, CDOM and SO42− in the ocean.

Global monitoring of terrestrial chlorophyll fluorescence from moderate-spectral-resolution near-infrared satellite measurements: methodology, simulations, and application to GOME-2

Directory of Open Access Journals (Sweden)

J. Joiner

2013-10-01

Full Text Available 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

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.

Some fluorescence properties of dimethylaminochalcone and its novel cyclic analogues

Science.gov (United States)

Tomečková, Vladimíra; Poškrobová, Martina; Štefanišinová, Miroslava; Perjési, Pál

2009-12-01

This paper demonstrates the basic character (polarity, solubility, colour, absorption and fluorescence quantum yield) of synthetic dimethylaminochalcone ( 1) and its cyclic analogues measured in toluene, chloroform, dimethylsulfoxide and ethanol, which have been studied by absorption and fluorescence spectroscopy. The biologically active dye 4'-dimethylaminochalcone ( 1b) and its less flexible analogues 4-dimethylaminoindanone ( 2b), -tetralone ( 3b), and -benzosuberone ( 4b) are lipophilic molecules that displayed the best solubility in toluene and chloroform. The highest fluorescence and quantum yields of compounds 1 and 2 have been obtained in DMSO and chloroform. Quenching effect of fluorescence compounds ( 1- 4) has been studied in the mixture of the most polar organic solvents DMSO and water. In the presence of water, fluorescence of compound 1 has been quenched the best from all studied chalcones and emission maxima of molecules 1- 4 have been shifted to the longer wavelengths. Quenching effect of fluorescence by water was in order 1 > 2 > 3 > 4.

Cytochrome P450 CYP89A9 Is Involved in the Formation of Major Chlorophyll Catabolites during Leaf Senescence in Arabidopsis[W][OA

Science.gov (United States)

Christ, Bastien; Süssenbacher, Iris; Moser, Simone; Bichsel, Nicole; Egert, Aurelie; Müller, Thomas; Hörtensteiner, Stefan

2013-01-01

Nonfluorescent chlorophyll catabolites (NCCs) were described as products of chlorophyll breakdown in Arabidopsis thaliana. NCCs are formyloxobilin-type catabolites derived from chlorophyll by oxygenolytic opening of the chlorin macrocycle. These linear tetrapyrroles are generated from their fluorescent chlorophyll catabolite (FCC) precursors by a nonenzymatic isomerization inside the vacuole of senescing cells. Here, we identified a group of distinct dioxobilin-type chlorophyll catabolites (DCCs) as the major breakdown products in wild-type Arabidopsis, representing more than 90% of the chlorophyll of green leaves. The molecular constitution of the most abundant nonfluorescent DCC (NDCC), At-NDCC-1, was determined. We further identified cytochrome P450 monooxygenase CYP89A9 as being responsible for NDCC accumulation in wild-type Arabidopsis; cyp89a9 mutants that are deficient in CYP89A9 function were devoid of NDCCs but accumulated proportionally higher amounts of NCCs. CYP89A9 localized outside the chloroplasts, implying that FCCs occurring in the cytosol might be its natural substrate. Using recombinant CYP89A9, we confirm FCC specificity and show that fluorescent DCCs are the products of the CYP89A9 reaction. Fluorescent DCCs, formed by this enzyme, isomerize to the respective NDCCs in weakly acidic medium, as found in vacuoles. We conclude that CYP89A9 is involved in the formation of dioxobilin-type catabolites of chlorophyll in Arabidopsis. PMID:23723324

Fluorescence quenching and the "ring-mode" to "red-mode" transition in alkali inductively coupled plasmas

Science.gov (United States)

Huang, M.; Bazurto, R.; Camparo, J.

2018-01-01

The ring-mode to red-mode transition in alkali metal inductively coupled plasmas (ICPs) (i.e., rf-discharge lamps) is perhaps the most important physical phenomenon affecting these devices as optical pumping light sources for atomic clocks and magnetometers. It sets the limit on useful ICP operating temperature, thereby setting a limit on ICP light output for atomic-clock/magnetometer signal generation, and it is a temperature region of ICP operation associated with discharge instability. Previous work has suggested that the mechanism driving the ring-mode to red-mode transition is associated with radiation trapping, but definitive experimental evidence validating that hypothesis has been lacking. Based on that hypothesis, one would predict that the introduction of an alkali-fluorescence quenching gas (i.e., N2) into the ICP would increase the ring-mode to red-mode transition temperature. Here, we test that prediction, finding direct evidence supporting the radiation-trapping hypothesis.

Label-free turn-on fluorescent detection of melamine based on the anti-quenching ability of Hg 2+ to gold nanoclusters.

Science.gov (United States)

Dai, Haichao; Shi, Yan; Wang, Yilin; Sun, Yujing; Hu, Jingting; Ni, Pengjuan; Li, Zhuang

2014-03-15

In this work, we proposed a facile, environmentally friendly and cost-effective assay for melamine with BSA-stabilized gold nanoclusters (AuNCs) as a fluorescence reader. Melamine, which has a multi-nitrogen heterocyclic ring, is prone to coordinate with Hg(2+). This property causes the anti-quenching ability of Hg(2+) to AuNCs through decreasing the metallophilic interaction between Hg(2+) and Au(+). By this method, detection limit down to 0.15 µM is obtained, which is approximately 130 times lower than that of the US food and Drug Administration estimated melamine safety limit of 20 µM. Furthermore, several real samples spiked with melamine, including raw milk and milk powder, are analyzed using the sensing system with excellent recoveries. This gold-nanocluster-based fluorescent method could find applications in highly sensitive detection of melamine in real samples. © 2013 Elsevier B.V. All rights reserved.

A study of the low-lying singlet and triplet electronic states of chlorophyll A and B

Directory of Open Access Journals (Sweden)

Etinski Mihajlo

2013-01-01

Full Text Available Chlorophylls have been extensively investigated both experimentally and theoretically owing to the fact that they are essential for photosynthesis. We have studied two forms of chlorophyll, chlorophyll a and chlorophyll b, by means of density functional theory. Optimization of S0, S1 and T1 states was performed with the B3-LYP functional. The computed fluorescence lifetimes show good agreement with the available experimental data. The electronic adiabatic energies of S1 and T1 states are 2.09/2.12 and 1.19/1.29 eV for chlorophyll a and chlorophyll b respectively. We discussed the implications of this results on the triplet formation. Also, the calculated vertical ionization potentials shows good agreement with the experimental results. [Projekat Ministarstva nauke Reoublike Srbije, br. 172040

Sensitive and selective detection of adenine using fluorescent ZnS nanoparticles

International Nuclear Information System (INIS)

Meerabai Devi, L; Negi, Devendra P S

2011-01-01

We have used fluorescent ZnS nanoparticles as a probe for the determination of adenine. A typical 2 x 10 -7 M concentration of adenine quenches 39.3% of the ZnS fluorescence. The decrease in ZnS fluorescence as a function of adenine concentration was found to be linear in the concentration range 5 x 10 -9 -2 x 10 -7 M. The limit of detection (LOD) of adenine by this method is 3 nM. Among the DNA bases, only adenine quenched the fluorescence of ZnS nanoparticles in the submicromolar concentration range, thus adding selectivity to the method. The amino group of adenine was important in determining the quenching efficiency. Steady-state fluorescence experiments suggest that one molecule of adenine is sufficient to quench the emission arising from a cluster of ZnS consisting of about 20 molecules. Time-resolved fluorescence measurements indicate that the adenine molecules block the sites on the surface of ZnS responsible for emission with the longest lifetime component. This method may be applied for the determination of adenine in biological samples since the measurements have been carried out at pH 7.

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

A Comparison between Local and Global Spaceborne Chlorophyll Indices in the St. Lawrence Estuary

Directory of Open Access Journals (Sweden)

Martin A. Montes-Hugo

2012-11-01

Full Text Available Spaceborne chlorophyll indices based on red fluorescence (wavelength = 680 nm and water leaving radiance (Lw in the visible spectrum (i.e., 400–700 nm were evaluated in the St Lawrence Estuary (SLE during September of 2011. Relationships between chlorophyll concentration (chl and fluorescence were constructed based on fluorescence line height (FLH measurements derived from a compact laser-based spectrofluorometer developed by ENEA (CASPER and using spectral bands corresponding to the satellite sensor MERIS (MEdium Resolution Imaging Spectrometer. Chlorophyll concentration as estimated from CASPER (chlCASPER was relatively high NE of the MTZ (upper Estuary, and nearby areas influenced by fronts or freshwater plumes derived from secondary rivers (lower estuary. These findings agree with historical shipboard measurements. In general, global chl products calculated from Lw had large biases (up to 27-fold overestimation and 50-fold underestimation with respect to chlCASPER values. This was attributed to the smaller interference of detritus (mineral + organic non-living particulates and chromophoric dissolved organic matter on chlCASPER estimates. We encourage the use of spectrofluorometry for developing and validating remote sensing models of chl in SLE waters and other coastal environments characterized by relatively low to moderate (<10 g·m−3 concentrations of detritus.

Assimilation of remotely sensed chlorophyll fluorescence data into the land surface model CLM4

Science.gov (United States)

Wieneke, S.; Ahrends, H. E.; Rascher, U.; Schween, J.; Schickling, A.; Crewell, S.

2013-12-01

Photosynthesis is the most important exchange process of CO2 between the atmosphere and the land-surface. Therefore, the prediction of vegetation response to environmental conditions like increasing CO2 concentrations or plant stress is crucial for a reliable prediction of climate change. Photosynthesis is a complex physiological process that consists of numerous bio-physical sub-processes and chemical reactions. Spatial and temporal patterns of photosynthesis depend on dynamic plant-specific adaptation strategies to highly variable environmental conditions. Photosynthesis can be estimated using land-surface models, but, while state-of-the-art models often rely on Plant Functional Type (PFT) specific constants, they poorly simulate the dynamic adaptation of the physiological status of plant canopies in space and time. Remotely sensed sun-induced chlorophyll fluorescence (SICF) gives us now the possibility to estimate the diurnal dynamic vitality of the photosynthetic apparatus at both, the leaf and canopy levels. We installed within the framework of the Transregio32 project (www.tr32.de) automated hyperspectral fluorescence sensors at an agricultural site (winter wheat) in the Rur catchment area in West Germany at the end of July 2012. End of August, additional measurements of SIFC on nearby temperate grassland site (riparian meadow) and on a sugar beet field were performed. Spatial covering SICF data of the region were obtained during a measurement campaign using the newly developed air-borne hyperspectral sensor HyPlant on the 23 and 27 August 2012. SIFC data and data provided by eddy covariance measurements will be used to update certain model parameters that are normally set as constants. First model results demonstrate that the assimilation of SIFC into the Community Land Model 4 (CLM4) will result in a more realistic simulation of plant-specific adaptation strategies and therefore in a more realistic simulation of photosynthesis in space and time.

Study of interaction between tryptophan, tyrosine, and phenylalanine separately with silver nanoparticles by fluorescence quenching method

International Nuclear Information System (INIS)

Roy, S.; Das, T.K.

2015-01-01

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 (ΔH, ΔS, and ΔG) 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. (authors)

Luminescence quenching by reversible ionization or exciplex formation/dissociation.

Science.gov (United States)

Ivanov, Anatoly I; Burshtein, Anatoly I

2008-11-20

The kinetics of fluorescence quenching by both charge transfer and exciplex formation is investigated, with an emphasis on the reversibility and nonstationarity of the reactions. The Weller elementary kinetic scheme of bimolecular geminate ionization and the Markovian rate theory are shown to lead to identical results, provided the rates of the forward and backward reactions account for the numerous recontacts during the reaction encounter. For excitation quenching by the reversible exciplex formation, the Stern-Volmer constant is specified in the framework of the integral encounter theory. The bulk recombination affecting the Stern-Volmer quenching constant makes it different for pulse excited and stationary luminescence. The theory approves that the free energy gap laws for ionization and exciplex formation are different and only the latter fits properly the available data (for lumiflavin quenching by aliphatic amines and aromatic donors) in the endergonic region.

Highly Sensitive Ratiometric Fluorescent Sensor for Trinitrotoluene Based on the Inner Filter Effect between Gold Nanoparticles and Fluorescent Nanoparticles.

Science.gov (United States)

Lu, Hongzhi; Quan, Shuai; Xu, Shoufang

2017-11-08

In this work, we developed a simple and sensitive ratiometric fluorescent assay for sensing trinitrotoluene (TNT) based on the inner filter effect (IFE) between gold nanoparticles (AuNPs) and ratiometric fluorescent nanoparticles (RFNs), which was designed by hybridizing green emissive carbon dots (CDs) and red emissive quantum dots (QDs) into a silica sphere as a fluorophore pair. AuNPs in their dispersion state can be a powerful absorber to quench CDs, while the aggregated AuNPs can quench QDs in the IFE-based fluorescent assays as a result of complementary overlap between the absorption spectrum of AuNPs and emission spectrum of RFNs. As a result of the fact that TNT can induce the aggregation of AuNPs, with the addition of TNT, the fluorescent of QDs can be quenched, while the fluorescent of CDs would be recovered. Then, ratiometric fluorescent detection of TNT is feasible. The present IFE-based ratiometric fluorescent sensor can detect TNT ranging from 0.1 to 270 nM, with a detection limit of 0.029 nM. In addition, the developed method was successfully applied to investigate TNT in water and soil samples with satisfactory recoveries ranging from 95 to 103%, with precision below 4.5%. The simple sensing approach proposed here could improve the sensitivity of colorimetric analysis by changing the ultraviolet analysis to ratiometric fluorescent analysis and promote the development of a dual-mode detection system.

Chlorophyll fluorescence response to water and nitrogen deficit

Science.gov (United States)

Cendrero Mateo, Maria del Pilar

The increasing food demand as well as the need to predict the impact of warming climate on vegetation makes it critical to find the best tools to assess crop production and carbon dioxide (CO2) exchange between the land and atmosphere. Photosynthesis is a good indicator of crop production and CO2 exchange. Chlorophyll fluorescence (ChF) is directly related to photosynthesis. ChF can be measured at leaf-scale using active techniques and at field-scales using passive techniques. The measurement principles of both techniques are different. In this study, three overarching questions about ChF were addressed: Q1) How water, nutrient and ambient light conditions determine the relationships between photosynthesis and ChF? Which is the optimum irradiance level for detecting water and nutrient deficit conditions with ChF? ; Q2) which are the limits within which active and passive techniques are comparable?; and Q3) What is the seasonal relationship between photosynthesis and ChF when nitrogen is the limiting factor? To address these questions, two main experiments were conducted: Exp1) Concurrent photosynthesis and ChF light-response curves were measured in camelina and wheat plants growing under (i) intermediate-light and (ii) high-light conditions respectively. Plant stress was induced by (i) withdrawing water, and (ii) applying different nitrogen levels; and Exp2) coincident active and passive ChF measurements were made in a wheat field under different nitrogen treatments. The results indicated ChF has a direct relationship with photosynthesis when water or nitrogen drives the relationship. This study demonstrates that the light level at which plants were grown was optimum for detecting water and nutrient deficit with ChF. Also, the results showed that for leaf-average-values, active measurements can be used to better understand the daily and seasonal behavior of passive ChF. Further, the seasonal relation between photosynthesis and ChF with nitrogen stress was not a

Carotenoid-induced non-photochemical quenching in the cyanobacterial chlorophyll synthase-HliC/D complex

Czech Academy of Sciences Publication Activity Database

Niedzwiedzki, D.M.; Tronina, T.; Liu, H.; Staleva, H.; Komenda, Josef; Sobotka, Roman; Blankenship, R.E.; Polívka, T.

2016-01-01

Roč. 1857, č. 9 (2016), s. 1430-1439 ISSN 0005-2728 R&D Projects: GA ČR GBP501/12/G055 Institutional support: RVO:61388971 Keywords : Carotenoids * Non-photochemical quenching * Energy transfer Subject RIV: CE - Biochemistry Impact factor: 4.932, year: 2016

Changes in the fluorescence of the Caribbean coral Montastraea faveolata during heat-induced bleaching

Science.gov (United States)

Zawada, David G.; Jaffe, J.S.

2003-01-01

In order to evaluate the response of commonly occurring green and orange fluorescent host-based pigments, a thermal stress experiment was performed on specimens of the Caribbean coral Montastraea faveolata. Seven paired samples were collected from a small oceanic reef near Lee Stocking Island in the Bahamas. Seven of the fourteen corals were subjected to elevated temperatures for 28 d, followed by a recovery period lasting 53 d. Throughout the experiment, high-resolution (~400 µm pixel-1) multispectral images of induced fluorescence were recorded at wavelengths corresponding to the green and orange host pigments, plus chlorophyll. These images revealed that the fluorescence of both host pigments was concentrated at polyp centers and declined by 70–90% in regions between polyps. Chlorophyll fluorescence, however, was distributed almost uniformly across the entire coral surface, but with decreases of 10–30% around polyp centers. A normalized difference ratio between the green and orange pigments (GO ratio) was developed to facilitate comparison with chlorophyll fluorescence as a bleaching indicator. Analysis showed a high correspondence between a sustained GO ratio of less than zero and the death of corals. Finally, this ratio was resistant to contamination from other sources of chlorophyll fluorescence, such as filamentous algae.

Zeaxanthin-independent energy quenching and alternative electron sinks cause a decoupling of the relationship between the photochemical reflectance index (PRI) and photosynthesis in an evergreen conifer during spring.

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