Absolute fluorescence measurements > 1000 nm: setup design, calibration and standards (Conference Presentation)

Bench-grafted Fuji/M26 apple trees were fertigated with different concentrations of nitrogen by using a modified Hoagland solution for 6 weeks, resulting in a range of leaf N from 1.0 to 4.3 g·m–2. Over this range, leaf absorptance increased curvilinearly from 75% to 92.5%. Under high light conditions (1500 (mol·m–2·s–1), the amount of absorbed light in excess of that required to saturate CO2 assimilation decreased with increasing leaf N. Chlorophyll fluorescence measurements revealed that the maximum photosystem II (PSII) efficiency of dark-adapted leaves was relatively constant over the leaf N range except for a slight drop at the lower end. As leaf N increased, non-photochemical quenching under high light declined and there was a corresponding increase in the efficiency with which the absorbed photons were delivered to open PSII centers. Photochemical quenching coefficient decreased significantly at the lower end of the leaf N range. Actual PSII efficiency increased curvilinearly with increasing leaf N, and was highly correlated with light-saturated CO2 assimilation. The fraction of absorbed light potentially used for free radical formation was estimated to be about 10% regardless of the leaf N status. It was concluded that increased thermal dissipation protected leaves from photo-oxidation as leaf N declined.

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A New Fluorescent Salen-uranyl Sensor for the Sub-ppm Detection of Chemical Warfare Agents

Current Organic Chemistry ◽

10.2174/1385272824999200930150313 ◽

2020 ◽

Vol 24 (20) ◽

pp. 2378-2382

Author(s):

Andrea Pappalardo ◽

Chiara M.A. Gangemi ◽

Rosa Maria Toscano ◽

Giuseppe Trusso Sfrazzetto

Keyword(s):

Real Time ◽

Fluorescent Sensor ◽

Chemical Warfare Agents ◽

Optical Response ◽

Chemical Warfare ◽

Lethal Effects ◽

Strong Affinity ◽

Chemical Attack ◽

Fluorescence Measurements ◽

Warfare Agents

Real-time sensing of Chemical Warfare Agents (CWAs) is today a crucial topic to prevent the lethal effects of a terroristic chemical attack. For this reason, the development of efficient, selective, sensitive and reversible sensoristic devices, able to detect by optical response ppm levels of these compounds, is strongly required. Here, the synthesis of a new fluorescent sensor based on a salen-uranyl scaffold, functionalized with two bodipy moieties, and its application for the detection of sub-ppm levels of CWAs is reported. Detection properties were evaluated by fluorescence measurements and selectivity tests demonstrated the strong affinity for CWAs.

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Chlorophyll Fluorescence Measurements in Arabidopsis Wild-type and Photosystem II Mutant Leaves

BIO-PROTOCOL ◽

10.21769/bioprotoc.1532 ◽

2015 ◽

Vol 5 (14) ◽

Cited By ~ 3

Author(s):

Iris Steinberger ◽

Felix Egidi ◽

Anja Schneider

Keyword(s):

Chlorophyll Fluorescence ◽

Photosystem Ii ◽

Wild Type ◽

Fluorescence Measurements

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E3 Ubiquitin Ligase SPL2 Is a Lanthanide-Binding Protein

International Journal of Molecular Sciences ◽

10.3390/ijms22115712 ◽

2021 ◽

Vol 22 (11) ◽

pp. 5712

Author(s):

Michał Tracz ◽

Ireneusz Górniak ◽

Andrzej Szczepaniak ◽

Wojciech Białek

Keyword(s):

Ubiquitin Ligase ◽

Conformational Changes ◽

Protein Interactions ◽

E3 Ubiquitin Ligase ◽

Lanthanide Ions ◽

E3 Ligases ◽

Fluorescence Measurements ◽

Partial Unfolding

The SPL2 protein is an E3 ubiquitin ligase of unknown function. It is one of only three types of E3 ligases found in the outer membrane of plant chloroplasts. In this study, we show that the cytosolic fragment of SPL2 binds lanthanide ions, as evidenced by fluorescence measurements and circular dichroism spectroscopy. We also report that SPL2 undergoes conformational changes upon binding of both Ca2+ and La3+, as evidenced by its partial unfolding. However, these structural rearrangements do not interfere with SPL2 enzymatic activity, as the protein retains its ability to auto-ubiquitinate in vitro. The possible applications of lanthanide-based probes to identify protein interactions in vivo are also discussed. Taken together, the results of this study reveal that the SPL2 protein contains a lanthanide-binding site, showing for the first time that at least some E3 ubiquitin ligases are also capable of binding lanthanide ions.

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A Nitronaphthalimide Probe for Fluorescence Imaging of Hypoxia in Cancer Cells

Journal of Fluorescence ◽

10.1007/s10895-021-02800-6 ◽

2021 ◽

Author(s):

Rashmi Kumari ◽

Vasumathy R ◽

Dhanya Sunil ◽

Raghumani Singh Ningthoujam ◽

Badri Narain Pandey ◽

...

Keyword(s):

Fluorescence Imaging ◽

Tumor Hypoxia ◽

Binding Pocket ◽

Docking Studies ◽

Single Step ◽

Naphthalic Anhydride ◽

Hypoxic Conditions ◽

Fluorescence Measurements ◽

Enzymatic Reduction

AbstractThe bioreductive enzymes typically upregulated in hypoxic tumor cells can be targeted for developing diagnostic and drug delivery applications. In this study, a new fluorescent probe 4−(6−nitro−1,3−dioxo−1H−benzo[de]isoquinolin−2(3H)−yl)benzaldehyde (NIB) based on a nitronaphthalimide skeleton that could respond to nitroreductase (NTR) overexpressed in hypoxic tumors is designed and its application in imaging tumor hypoxia is demonstrated. The docking studies revealed favourable interactions of NIB with the binding pocket of NTR-Escherichia coli. NIB, which is synthesized through a simple and single step imidation of 4−nitro−1,8−naphthalic anhydride displayed excellent reducible capacity under hypoxic conditions as evidenced from cyclic voltammetry investigations. The fluorescence measurements confirmed the formation of identical products (NIB-red) during chemical as well as NTR−aided enzymatic reduction in the presence of NADH. The potential fluorescence imaging of hypoxia based on NTR-mediated reduction of NIB is confirmed using in-vitro cell culture experiments using human breast cancer (MCF−7) cells, which displayed a significant change in the fluorescence colour and intensity at low NIB concentration within a short incubation period in hypoxic conditions. Graphical abstract

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Fluorescent Orthopalladated Complexes of 4-Aryliden-5(4H)-Oxazolones from the Kaede Protein: Synthesis and Characterization

Molecules ◽

10.3390/molecules26051238 ◽

2021 ◽

Vol 26 (5) ◽

pp. 1238

Author(s):

Eduardo Laga ◽

David Dalmau ◽

Sofía Arregui ◽

Olga Crespo ◽

Ana I. Jimenez ◽

...

Keyword(s):

Intramolecular Interactions ◽

Ortho Position ◽

Fluorescent Properties ◽

Ancillary Ligands ◽

X Ray ◽

Mononuclear Complexes ◽

Fluorescence Measurements ◽

Anionic Ligands ◽

Order Of Magnitude

The goal of the work reported here was to amplify the fluorescent properties of 4-aryliden-5(4H)-oxazolones by suppression of the hula-twist non-radiative deactivation pathway. This aim was achieved by simultaneous bonding of a Pd center to the N atom of the heterocycle and the ortho carbon of the arylidene ring. Two different 4-((Z)-arylidene)-2-((E)-styryl)-5(4H)-oxazolones, the structures of which are closely related to the chromophore of the Kaede protein and substituted at the 2- and 4-positions of the arylidene ring (1a OMe; 1b F), were used as starting materials. Oxazolones 1a and 1b were reacted with Pd(OAc)2 to give the corresponding dinuclear orthometalated palladium derivates 2a and 2b by regioselective C–H activation of the ortho-position of the arylidene ring. Reaction of 2a (2b) with LiCl promoted the metathesis of the bridging carboxylate by chloride ligands to afford dinuclear 3a (3b). Mononuclear complexes containing the orthopalladated oxazolone and a variety of ancillary ligands (acetylacetonate (4a, 4b), hydroxyquinolinate (5a), aminoquinoline (6a), bipyridine (7a), phenanthroline (8a)) were prepared from 3a or 3b through metathesis of anionic ligands or substitution of neutral weakly bonded ligands. All species were fully characterized and the X-ray determination of the molecular structure of 7a was carried out. This structure has strongly distorted ligands due to intramolecular interactions. Fluorescence measurements showed an increase in the quantum yield (QY) by up to one order of magnitude on comparing the free oxazolone (QY < 1%) with the palladated oxazolone (QY = 12% for 6a). This fact shows that the coordination of the oxazolone to the palladium efficiently suppresses the hula-twist deactivation pathway.

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