Blue-green Fluorescence Emission Research Articles

Tetraphenylethylene based amphiphilic derivatives: The self-assembly, photo-responsiveness and their application for erasable fluorescent ink

Since the discovery of aggregation induced emission (AIE) phenomenon, various stimuli-responsive materials have been rapidly developed. However, the development of self-assembled amphiphilic light-responsive materials in aqueous solution needs to be solved urgently. In this work, three new amphiphilic tetraphenylethylene (TPE) derivatives (TPE-1, TPE-2 and TPE-3) with AIE properties and photochromism were synthesized and investigated. Owing to the different electron-donating abilities of the three groups attached to TPE units, the TPE-1, TPE-2 and TPE-3 displayed blue-green, yellow-green, and orange fluorescence emission in the aggregation state respectively. Furthermore, ordered nanoparticles formed via self-assembly in aqueous solution showed interesting photocyclization behaviors, which lead to fluorescence quenching under ultraviolet light irradiation (λ = 365 nm). Therefore, the compounds can be used as anti-counterfeiting ink in the information encryption due to their amphiphilicity and photo-responsiveness. This work contributes new members to the amphiphilic light-responsive materials family and demonstrates the potential for applications in the fields of optical information storage, information security protection, and erase/rewrite systems.

A chromone derivative as a colorimetric and “ON-OFF-ON” fluorescent probe for highly sensitive and selective detection of Cu2+ and S2−

A chromone derivative (L) which could be utilized for reversibly detecting Cu2+ and S2− by means of fluorescence quenching and displacement in aqueous solution was designed and developed. Upon the addition of Cu2+, the strong blue-green fluorescence emission of L was quenched rapidly and then recovered in 1 min by successively adding S2−. Furthermore, with the alternate addition of Cu2+ and S2−, the reversible cycles could be repeated for at least four times, which meant that L could be identified as a renewable dual-functioning probe. What's more, due to its excellent sensing performances, this probe L could also be used to detect Cu2+ and S2− with test strips conveniently.

Fluorescence copolymer-based dual-signal monitoring tyrosinase activity and its inhibitor screening via blue-green emission transformation.

Tyrosinase (TYR) is a crucial enzyme in melanin metabolism and catecholamine production, its abnormal overexpression is closely associated with many human diseases involving melanoma cancer, vitiligo, Parkinson's disease and so on. Herein, a dual-signal fluorescence sensing system for monitoring TYR activity is constructed depending on the transformation of blue-green fluorescence emission of copolymer. The developed sensing system is based on TYR catalyzing the hydroxylation of mono-phenol to o-diphenol and the conversion of fluorescence copolymer (FCP) blue emission (430nm) and green emission (535nm) in the presence of PEI. In the system, both blue and green emission exhibit a high selectivity and sensitivity (S/B up to 300 and 30 for blue and green emission, respectively) toward TYR in the range from 0.5 to 2.5U/mL with the detection limit of 0.002U/mL and 0.06U/mL, respectively. Additionally, this assay is used to detect TYR in human serum with excellent recovery even at 30% human serum concentrations. Furthermore, it still has been successfully applied to TYR inhibitor screening by taking kojic acid as a model. We believe that our developed sensor has great potential application in TYR-associated disease diagnosis and treatment and drug discovery.

Effective and selective removal of heavy metals from industrial effluents using sustainable Si–CD conjugate based column chromatography

The present investigation deals with the green synthesis of aqueous-stable and highly fluorescent carbon dots (CD) by hydrothermal treatment of tender leaf extract of Ficus benghalensis. The synthesized CD was characterized. Carbon dots were of an average size of 2.28 nm with a blue-green fluorescence emission at 317 nm and showed high selectivity and specificity for iron and nickel amongst the different tested heavy metals with a LOD of 0.0015 μmol/mL and 0.000014 μmol/mL respectively. Further, we functionalized silica with the prepared carbon dot to generate an adsorbent for purification of contaminated water. A short bed adsorbed column system was designed for determining the efficiency of adsorption. As envisioned approximately, 77% and 74% removal of Fe and Ni was observed when the metal salts were eluted individually. Purification efficacy was analysed using an industrial electroplating effluent, which showed adsorption of 74% and 79% for Fe and Ni respectively.

Solvatochromic and application in dye-sensitized solar cells of sandwich-like Cd(II) complexes: supramolecular architectures based on N(1),N(3)-bis[(6-methoxypyridin-2-yl)methylene]benzene-1,3-diamine.

A novel polydentate Schiff base ligand N(1),N(3)-bis[(6-methoxypyridin-2-yl)methylene]benzene-1,3-diamine (L) and its two dinuclear sandwich-like complexes {[CdL(NO3)(H2O)]·NO3}2 (1) and {[CdL(CH3CN)(H2O)]·(ClO4)2·(CH3CN)2}2 (2) were synthesized. Both C-H∙∙∙O, C-H∙∙∙N and π-π non-covalent interactions had essential roles in constructing the resulting three-dimensional supramolecular networks. L emits a more intense blue-green fluorescence emission around 493 nm than in dilute solution, exhibiting stacking-induced emission properties. Complexes 1 and 2 exhibited the dual properties of exceptional solvatochromism and fluorescence quenching towards CH3OH molecules. As these compounds could overcome the absent absorption of ruthenium complex N719 in the low wavelength region of the visible spectrum, offset the competitive visible light absorption of I3(-) and reduce the charge recombination of injected electrons, the Schiff base ligand l and complexes 1 and 2 were used as co-sensitizers in combination with N719 to investigate their effect on enhancing the performance of dye-sensitized solar cells. A short circuit current density of 14.37 mA cm(-2), an open-circuit voltage of 0.71 V and a fill factor of 0.61 corresponding to an overall conversion efficiency of 6.17% under AM 1.5 G solar irradiation were achieved when 1 was used as a co-sensitizer, which are much higher than the results obtained for dye-sensitized solar cells sensitized by N719 alone (5.06%).

Imaging of multi-color fluorescence emission from leaf tissues

Multi-color fluorescence emission from leaf tissues is presented as a powerful reporter on plant biochemistry and physiology that can be applied both at macro- and micro-scales. The blue-green fluorescence emission is typically excited by ultraviolet (UV) excitation. However, this approach cannot be applied in investigating intact leaf interior because the UV photons are largely absorbed in the epidermis of the leaf surface. This methodological barrier is eliminated by replacing the UV photon excitation by excitation with two infra-red photons of the same total energy. We demonstrate this approach by using two-photon excitation for microscopy of Arabidopsis thaliana leaves infected by pathogenic bacterium Pseudomonas syringae. The leaf structures are visualized by red chlorophyll fluorescence emission reconstructed in 3-D images while the bacteria are detected by the green emission of engineered fluorescence protein.

Scientific and technical challenges in remote sensing of plant canopy reflectance and fluorescence

State-of-the-art optical remote sensing of vegetation canopies is reviewed here to stimulate support from laboratory and field plant research. This overview of recent satellite spectral sensors and the methods used to retrieve remotely quantitative biophysical and biochemical characteristics of vegetation canopies shows that there have been substantial advances in optical remote sensing over the past few decades. Nevertheless, adaptation and transfer of currently available fluorometric methods aboard air- and space-borne platforms can help to eliminate errors and uncertainties in recent remote sensing data interpretation. With this perspective, red and blue-green fluorescence emission as measured in the laboratory and field is reviewed. Remotely sensed plant fluorescence signals have the potential to facilitate a better understanding of vegetation photosynthetic dynamics and primary production on a large scale. The review summarizes several scientific challenges that still need to be resolved to achieve operational fluorescence based remote sensing approaches.

Ecophysiological approach to study of the role of cell-bound peroxidase forms in wheat leaves of different morphology

Extracellular peroxidase enzymes, both ionically - and covalently bound, have been implicated in the biochemical changes of cell wall and furthermore for regulation of leaf and root extension growth. However, the role of cell wall bound peroxidase in changes of mature leaf morphology is poorly understood. The aim of this study was to determine whether ionically and covalently bound peroxidase activities exhibit any relationships with drought-induced leaf rolling of wheat. An activity and thermostability of three wheat genotypes with different leaf rolling degree were studied. The results clearly show that two genotypes with leaf rolling trait exhibited significantly higher activity of both extracellular peroxidase fractions in comparison to non-rolling cv. 'Omskaya 9'. In addition, the significant genotypic differences were found in thermostability of ionically and covalently bound peroxidase. A 35 °C-treatment decreased the activity of ionically bound peroxidase (IBP) in non-rolling leaves of parent cultivar and enhanced the activity of IBP in rolling leaves of 'Alba' genotype. Under 45 and 55 °C-treatment the IBP was more stable in rolling leaves of both genotypes 'Otan' and 'Alba'. Despite to low activity of covalently bound peroxidase it was more stable after heating by 45 °C compare with ionically bound fraction. The heating of covalently bound peroxidase (CBP) extracts by 35 °C and 45 °C also has enhancing effect on its activity by both leaf rolling genotypes (on 16 and 40% by 'Otan' and 'Alba', respectively). At the same time the CBP activity of non-rolling genotype decreased significantly on 40%. Even after 55 °C-treatment the CBP of both rolling genotypes remained very stable, although there were further inhibition of CBP purificated from leaves of non-rolling genotype. Both wheat genotypes with inserted leaf rolling trait exhibited a much higher blue-green fluorescence emission than non-rolling leaves of parent cultivar 'Omskaya 9'. Thus, the molecular mechanism of leaf rolling regulation seems to include an adjustment of cell wall properties and probably involves an activity of cell wall bound peroxidase. Further investigation is expected to reveal the regulatory mechanism for leaf rolling in wheat.

Longitudinal leaf gradients of UV-absorbing screening pigments in barley (Hordeum vulgare).

In vivo leaf characteristics were examined to describe longitudinal gradients of UV-absorbing screening pigments in barley. Chlorophyll fluorescence properties and in vivo absorption spectra (210-750 nm) of leaves were measured from the base to the tip. Barley leaves showed strong longitudinal gradients of chlorophyll, where chlorophyll concentration increased within the first 5-8 cm from the leaf base, and did not significantly change for the remaining part of the leaf. Fluorescence microscopy was used to localize cell wall bound screening pigments different from flavonoids, since flavonoids lack a blue-green fluorescence emission (Lichtenthaler and Schweiger 1998). Measurements of in vivo chlorophyll fluorescence indicated that the ratio of UV-absorbing screening pigments per leaf area increases from the leaf base to the tip. These gradients were confirmed by in vivo absorption spectra. It is demonstrated that leaves in the early stage of development are less protected against UV-radiation than fully developed mature leaf regions. The experiments show that measurements of in vivo chlorophyll fluorescence are ideally suited as a fast non-invasive tool to estimate the epidermal UV-transmittance in different leaf sections.

Light-induced dynamic changes of NADPH fluorescence in Synechocystis PCC 6803 and its ndhB-defective mutant M55.

Blue-green fluorescence emission of intact cells of Synechocystis PCC6803 and of its ndhB-defective mutant M55 was measured with a standard pulse-amplitude-modulation chlorophyll fluorometer equipped with a new type of emitter-detector unit featuring pulse-modulated UV-A measuring light and a photomultiplier detector. A special illumination program of repetitive saturating light pulses with intermittent dark periods (10 s light, 40 s dark) was applied to elicit dynamic fluorescence changes under conditions of quasi-stationary illumination. The observed effects of artificial electron acceptors and inhibitors on the responses of wild-type and mutant M55 cells lead to the conclusion that changes of NAD(P)H fluorescence are measured. In control samples, a rapid phase of light-driven NADP reduction is overlapped by a somewhat slower phase of NADPH oxidation which is suppressed by iodoacetic acid and, hence, appears to reflect NADPH oxidation by the Calvin cycle. Mercury chloride transforms the light-driven positive response into a negative one, suggesting that inhibition of NADP reduction at the acceptor side of PSI leads to reduction of molecular oxygen, with the hydrogen peroxide formed (via superoxide) causing rapid oxidation of NADPH. The new fluorescence approach opens the way for new insights into the complex interactions between photosynthetic and respiratory pathways in cyanobacteria.

Changes in Blue-Green and Chlorophyll Fluorescence Emission and Fluorescence Ratios during Senescence of Tobacco Plants

Blue-green fluorescence and the red/far-red chlorophyll (Chl) fluorescence emission spectra of green tobacco leaves and of aurea leaves in different stages of senescence were measured using excitation at 355 nm in order to test the suitability of the fluorescence ratios green/red and green/far-red together with other ratios as stress and pigment indicators. Young yellowish-green leaves of the aurea mutant tobacco showed a much higher blue-green fluorescence emission and lower chlorophyll fluorescence as compared to the green wild type tobacco. As a consequence, the fluorescence intensity ratios blue/green ( F440/ F520), blue/red ( F440/ F690), blue/far-red ( F440/ F740), green/red ( F520/ F690) and green/far-red ( F520/ F740), as determined from the measured fluorescence emission spectra of the adaxial and abaxial leaf sides, were quite different for both leaf types and were functions of the content of chlorophylls and carotenoids. As chlorophyll levels decreased in senescing leaves of the aurea tobacco plant, the Chl a/ b ratio remained high at 3.3 to 4.0, while the ratio of chlorophylls to carotenoids declined slightly. In contrast, the Chl fluorescence ratios ( R fd 690-values, F v / F m and F v / F 0) as physiological indicators continuously declined, indicating a successive loss of photosynthetic activity. Values of the chlorophyll fluorescence ratio F690/ F740 for adaxial and abaxial leaf-sides increased with yellowing, whereas F440/ F520 tended to decrease with the senescence-induced decline in Chl content. F440/ F690 and F520/ F690 were found to increase after an initial decrease, with leaf age and senescence. The same trend was found for F440/ F740 and F520/ F740, which exhibited maximum sensitivity with respect to Chl breakdown. Whereas the F690/ F740 ratio for abaxial versus adaxial leaf surfaces correlated linearly, with the abaxial leaf-side values always being higher than the adaxial leaf-side, values for both sides corresponded in a curvilinear fashion with leaf Chl content. Changes during early stages of leaf development were seen not only in the most commonly used red/far-red ratio, F690/ F740, but to some extent also in F440/ F520. The results indicate that changes in photosynthetic activity due to senescence and Chl breakdown can easily be detected and qualified via fluorescence ratios that are based on the UV-A excited fluorescence bands F440, F520, F690 and F740. These ratios provide a solid basis for the laser-induced remote sensing of the state of health and Chl content of vegetation. The fluorescence ratios green/red and green/far-red were found to be very suitable complementary indicators of early stress events in plants.

Three‐color flow cytometry analysis of tricistronic expression of eBFP, eGFP, and eYFP using EMCV‐IRES linkages

Background: The ability to quickly analyze and sort double or triple fluorescent reporter constructs using simultaneous analysis provides significant flexibility in the solution of analytical and process-related questions in biotechnology. Methods: Bicistronic eBFP/eGFP and eBFP/eYFP constructs were made on two mammalian episomal plasmids using an internal ribosomal entry sequence from encephalomyocarditis virus (EMCV-IRES) to link two GFP expressions. Simultaneous two-color flow cytometry (FCM) analysis was accomplished using a dual Argon-laser multi-line configuration set at excitation wavelengths of 360 and 488 nm. Blue fluorescence emission (440 nm) and green fluorescence emission (507 nm) were detected using 405/20 (FL4) and 510/20 (FL1) bandpass filters. Dual eBFP/eYFP and three-color simultaneous analysis of eBFP/eGFP/eYFP was accomplished using the dual-laser configuration but also using a short-pass (525-nm) dichroic mirror and 550/30 bandpass filter configuration to detect yellow fluorescence emission (527 nm) in a third channel (FL2). Results: Human 293 cells transfected with the bicistronic construct of eBFP-IRES-eGFP were easily detected using simultaneous analysis, and the signals were well separated with a mean blue fluorescent intensity (MFI) in the 2nd-log decade (FL4) and green MFI in the 4th-log decade (FL1). Likewise, eBFP-IRES-eYFP transfected cells were as easily detected and also demonstrated very good signal separation. A tricistronic construct of eBFP-IRES-eGFP-IRES-eYFP was also made and transfected into 293 cells. Triple-color fluorescent cells were easily detected using the cytometer configuration for simultaneous analysis. All three signals separated with only moderate compensation required for green and yellow emission spectra. The respective MFI for each of the fluorescent proteins was correlative to what had been observed with the separate bicistronic constructs. Conclusions: Our results demonstrate that we have developed a novel fluorescent flow cytometry method that can be used as a powerful tool to differentiate and analyze three colors simultaneously from either a dual or a triple cistronic construct which has been transfected into living cells. Cytometry 37:51–59, 1999. © 1999 Wiley-Liss, Inc.

Three-color flow cytometry analysis of tricistronic expression of eBFP, eGFP, and eYFP using EMCV-IRES linkages

The ability to quickly analyze and sort double or triple fluorescent reporter constructs using simultaneous analysis provides significant flexibility in the solution of analytical and process-related questions in biotechnology. Bicistronic eBFP/eGFP and eBFP/eYFP constructs were made on two mammalian episomal plasmids using an internal ribosomal entry sequence from encephalomyocarditis virus (EMCV-IRES) to link two GFP expressions. Simultaneous two-color flow cytometry (FCM) analysis was accomplished using a dual Argon-laser multi-line configuration set at excitation wavelengths of 360 and 488 nm. Blue fluorescence emission (440 nm) and green fluorescence emission (507 nm) were detected using 405/20 (FL4) and 510/20 (FL1) bandpass filters. Dual eBFP/eYFP and three-color simultaneous analysis of eBFP/eGFP/eYFP was accomplished using the dual-laser configuration but also using a short-pass (525-nm) dichroic mirror and 550/30 bandpass filter configuration to detect yellow fluorescence emission (527 nm) in a third channel (FL2). Human 293 cells transfected with the bicistronic construct of eBFP-IRES-eGFP were easily detected using simultaneous analysis, and the signals were well separated with a mean blue fluorescent intensity (MFI) in the 2nd-log decade (FL4) and green MFI in the 4th-log decade (FL1). Likewise, eBFP-IRES-eYFP transfected cells were as easily detected and also demonstrated very good signal separation. A tricistronic construct of eBFP-IRES-eGFP-IRES-eYFP was also made and transfected into 293 cells. Triple-color fluorescent cells were easily detected using the cytometer configuration for simultaneous analysis. All three signals separated with only moderate compensation required for green and yellow emission spectra. The respective MFI for each of the fluorescent proteins was correlative to what had been observed with the separate bicistronic constructs. Our results demonstrate that we have developed a novel fluorescent flow cytometry method that can be used as a powerful tool to differentiate and analyze three colors simultaneously from either a dual or a triple cistronic construct which has been transfected into living cells.

Cell wall bound ferulic acid, the major substance of the blue-green fluorescence emission of plants

Summary When excited by UV-A radiation (e.g. N 2 -laser 337 nm), leaves of green plants exhibit, in addition to the red and far-red chlorophyll fluorescence, a genuine blue-green fluorescence emission with a maximum near 440–460 nm and a lower shoulder near 520–530 nm. Members of the Poaceae (monocotyledonous plants), e.g. maize ( Zea mays L.), wheat ( Triticum aestivum L.) or oat ( Auma sativa L.), possessed a much higher blue-green fluorescence emission than leaves of dicotyledonous plants, such as spinach ( Spinacia oleracea L.), tobacco ( Nicotiana tabacum L.), sunflower ( Helianthus annuus L.), foxtail ( Amaranthus caudatus L.) or purslane ( Portulaca oleracea L.). In the measured dicotyledonous plants, the blue-green fluorescence was in a similar range or considerably lower than the red chlorophyll fluorescence. In contrast, in Poaceae and other monocotyledonous plants, the blue-green fluorescence was generally several times higher than the red chlorophyll fluorescence. By alkaline hydrolysis of cell walls it was shown that the members of Poaceae exhibit a several times higher content of the blue-green fluorescent ferulic acid, both on leaf area and on a dry weight basis, than dicotyledonous plants, such as spinach, foxtail and purslane. Ferulic acid, being covalendy bound to the cell wall, appears to be the main emitter of the blue-green fluorescence of leaves which has been documented by several complementary observations. Other cell wall bound cinnamic acids (caffeic acid, p-coumaric acid), which are present in some plants in low amounts, contribute very little to the overall blue-green fluorescence emission of leaves. This also applies to the extractable flavonoids and cinnamic acids of the vacuole. The high fluorescence yield of ferulic acid containing cell walls is also documented by fluorescence excitation spectra of isolated, dried cell walls before and after alkaline hydrolysis of ferulic acid. Plants which do not possess ferulic acid in their cell walls, such as sunflower, pumpkin ( Cucurbita fici-folia L.) or tobacco, exhibit only a very faint blue-green fluorescence emission. Outdoor plants contained much higher levels of extractable flavonoids and cinnamic acids than greenhouse plants, yet the blue-green fluorescence was hardly modified indicating that the soluble flavonoids and cinnamic acids of the vacuole do not or only very little contribute to the blue-green fluorescence emission of plants.

Detection of Vegetation Stress Via a New High Resolution Fluorescence Imaging System

The UV-laser ( λ 355 nm) induced fluorescence emission spectra of green leaves comprise the blue(F440) and green (F520) fluorescence bands as well as the red (F690) and far-red (F740) chlorophyll fluorescence emission bands. Based on the four UV-laser induced fluorescence bands blue, green, red and farred a high resolution fluorescence imaging system was established, which allows a fast and large scale screening of fluorescence gradients and local disturbances in fluorescence emission over the whole leaf surface. The new imaging method not only permits to screen leaves by means of images in four fluorescence bands (LIF images) but, in addition, via images of the fluorescence ratios blue/red (F440/F690), blue/farred (F440/F740), the chlorophyll fluorescence ratio red/far-red (F690/F740) and the ratio blue/green (F440/F520) (LIF ratio images). By fluorescence imaging we could prove that in aurea tobacco the major part of the leaves' blue and green fluorescence is emitted from the main and side leave veins, whereas the major part of the leaves' red and far-red chlorophyll fluorescence is emitted from the vein-free leaf regions, which also have the highest chlorophyll content. A smaller proportion of the aurea tobacco leaves' blue-green fluorescence emission is derived from the cell walls of epidermis cells. The fluorescence ratios blue/red and blue/far-red are very sensitive to environmental changes, and thus permit early stress and strain detection in plants, and the evaluation of damage to the photosynthetic apparatus. Via monitoring the increase in chlorophyll fluorescence LIF images allow to detect differences in the time-dependent uptake of diuron and the progressing inhibition of photosynthetic electron transport in the treated leaf part. The novel fluorescence imaging technique sets a new dimension for early stress detection in the photosynthetic apparatus and in plants. It has many advantages over the previously applied point-data measurements of selected leaf points using conventional spectrofluorometers. The new fluorescence imaging system proved to be very suitable for remote sensing of plants in the near distance, and can be further developed for far distance remote sensing of the state of health of terrestrial vegetation. Some examples in the many possible ways of computer-aided fluorescence data processing (formation of different fluorescence ratios, screening of fluorescence profiles, histogramme plotting) are indicated.

Fluorescence Imaging of Water and Temperature Stress in Plant Leaves

Summary Fluorescence images of leaves from tobacco plants (green wild type and aurea mutant) were determinedin the blue (F440), green (F520), red (F690) and far-red region (F740), and also expressed as fluorescence ratio images. Under long-term water stress tobacco plants initially showed constant ratios of the blue to red fluorescence (F440/F690) and the blue to far-red fluorescence (F440/F740). Below a distinct threshold in water content (84° in green and 88° in aurea tobacco), however, a linear increase of the fluorescence ratios blue/red and blue/far-red was observed. This was due to a distinct increase in the bluegreen fluorescence emission, whereas the red and far-red chlorophyll fluorescence increased to a lower proportion. These changes in fluorescence ratios could easily be monitored by high resolution fluorescence imaging of whole leaves. For each point of the leaf, the fluorescence ratio can be read from the fluorescence ratio images of the leaves. In contrast, a short-term heat plus water stress in green tobacco plants was very fast detected via fluorescence imaging as a significant increase of red and far-red chlorophyll fluorescence emission (F690 and F740) on the leaf rim, whereas the central part of the leaf still exhibited the regular fluorescence signatures of photosynthetically active leaves. A combined outdoor stress (light, heat and water stress) at a dry sunny summer period was detected in Rhododendron by fluorescence imaging due to a much reduced red and far-red chlorophyll fluorescence. The latter was caused by UV-absorbing substances (e.g. flavonols) which accumulated primarily in the epidermis of these stressed leaves. These compounds seemed to act as UV-radiation filter, thus reducing the amount of the UV-excitation radiation, which could penetrate the mesophyll and which resulted in a reduced chlorophyll fluorescence excitation and emission. These results demonstrate that fluorescence imaging of leaves in the blue, green, red and far-red emission bands is an excellent tool for an early stress detection in plants, which is much superior to the hitherto applied spectral point data measurements.

Spectral characteristics and a possible topological assignment of blue green fluorescence excited by UV laser on leaves of unrelated species

For a number of years it has been known that a relatively strong fluorescence emission is produced by leaves when using UV radiation for excitation (Chappelle et al., 1984a); the apparent bandwidth is larger than 150 nm starting from 400 nm and includes several peaks; under excitation at 337 nm, their integrated energy is 6–11 times the energy released by chlorophyll (a) bands. The problem of bands assignment concerns relative contribution balance as several different emitters are located in chloroplasts, vacuoles, mitochondria, nuclei, cell wall, and epidermis. Within the sensitivity of a 4-λ synchronous pulse amplified N 2 laser photometer, and the experimental limits of a continuous spectrofluorimeter, the conclusion we present here is that. a) The blue-green fluorescence emission comes mainly from other epidermal layers; b) it is transferable on a quartz lamina by quick dipping the leaves in organic solvents and subsequent solvent evaporation; c) it shows a typical diffusion controlled quenching of fluorescence intensity within a thermal window between 277 K (high fluorescence) and 310 K (low fluorescence); d) the fluorescence emissivity is not linked to short-term metabolic arrangements, but tends to follow long-term epidermis adaptations to drought, and excessive radiation.

Blue-green laser-induced fluorescence from intact leaves: actinic light sensitivity and subcellular origins

Remote sensing of the health status of vegetation should be possible by using UV laser-induced fluorescence; nevertheless, the molecular origin of the leaf blue-green fluorescence emission is still unknown. In order to investigate possible relations of this fluorescence to the photosynthetic apparatus, we looked for its intensity changes after the addition of actinic light. The lack of any changes outside the chlorophyll fluorescence bands (Kautsky effect) was further investigated by collecting spectra from cell, protoplast, and chloroplast suspensions. These spectra led us to ascribe most of the blue-green laser-induced fluorescence that is detectable on a leaf by UV laser excitation to extrachloroplastic compartments. In active chloroplast suspensions blue fluorescence from photosynthetically reduced nicotinamide adenine dinucleotide phosphate (NADPH) has been detected and should be characterized by time-resolved fluorescence techniques.

Biogenic amines in the nervous system of the boll weevil, Anthanomous Grandis

1. The biogenic amines of the ventral nerve chord (VNC) of the boll weevil, Anthanomous grandis, were analyzed by histochemical techniques and liquid chromatography with electrochemical detection (LCEC). 2. Histochemical analysis with glyoxylic acid, but not formaldehyde, revealed a blue-green fluorescence (emission maximum between 435 and 470 nm) in the abdominal and subesophageal ganglia of the brain but inconsistent fluorescence in the thoracic ganglia. 3. A marked fluorescence observed in day 1, 2, 5 and 6 post-pupal females was variable in day 3–4 females. 4. LCEC analyses revealed the presence of l-dihydroxyphenylalanine, norepinephrine, dopamine and a fourth catecholamine tentatively identified as deoxyepinephrine.