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Fluorescence Lifetime

Xiaoyan Wang, Zhenjiang Liu, Wanying Zhao, Jianfan Sun, Bin Qian, Xinwei Wang, Huawei Zeng, Daolin Du, Jinsheng Duan
A novel fluorescent sensor based on bovine serum albumin stabilized gold/silver nanoclusters (BSA-Au/Ag NCs) was developed for sensitive and facile detection of alkaline phosphatase (ALP) activity. For this fluorescent sensor, ascorbic acid 2-phosphate (AAP) was decomposed into ascorbic acid (AA) and phosphate by catalysis with ALP. The initial red fluorescence of the BSA-Au/Ag NCs was effectively quenched by KMnO4 and then the fluorescence was recovered by addition of AA. The mechanism of interaction between BSA-Au/Ag NCs and KMnO4 and AA was studied with use of the fluorescence lifetime and UV-vis absorption spectra...
December 15, 2018: Analytical and Bioanalytical Chemistry
Charles-Henri Hage, Pierre Leclerc, Marc Fabert, Sylvia M Bardet, Julien Brevier, Guillaume Ducourthial, Tigran Mansuryan, Aymeric Leray, Alexandre Kudlinski, Frédéric Louradour
A two-photon fluorescence lifetime (2P-FLIM) microendoscope, capable of energetic metabolism imaging through the intracellular NADH autofluorescence, at sub-cellular resolution, is demonstrated. It exhibits readily usable characteristics such as convenient endoscope probe diameter (≈ 2 mm), fiber length (> 5 m) and data accumulation rate (16 frames per second (fps), leading to a FLIM refreshing rate of ≈ 0.1 to 1 fps depending on the sample) . The spiral scanning image formation does not influence the Instrument Response Function (IRF) characteristics of the system...
December 11, 2018: Journal of Biophotonics
Simon P Poland, Grace K Chan, James A Levitt, Nikola Krstajić, Ahmet T Erdogan, Robert K Henderson, Maddy Parsons, Simon M Ameer-Beg
In this Letter, we will discuss the development of a multifocal multiphoton fluorescent lifetime imaging system where four individual fluorescent intensity and lifetime planes are acquired simultaneously, allowing us to obtain volumetric data without the need for sequential scanning at different axial depths. Using a phase-only spatial light modulator (SLM) with an appropriate algorithm to generate a holographic pattern, we project a beamlet array within a sample volume of a size, which can be preprogrammed by the user...
December 15, 2018: Optics Letters
Ning Ma, Gopakumar Kamalakshakurup, Mohammad Aghaamoo, Abraham P Lee, Michelle A Digman
Characterization of single cell metabolism is imperative for understanding subcellular functional and biochemical changes associated with healthy tissue development and the progression of numerous diseases. However, single-cell analysis often requires the use of fluorescent tags and cell lysis followed by genomic profiling to identify the cellular heterogeneity. Identifying individual cells in a noninvasive and label-free manner is crucial for the detection of energy metabolism which will discriminate cell types and most importantly critical for maintaining cell viability for further analysis...
December 11, 2018: Cytometry. Part A: the Journal of the International Society for Analytical Cytology
Elizabeth J Osterlund, Nehad Hirmiz, Christian Tardif, David W Andrews
The Bcl-2 proteins control cell death via interchanging interactions within the Bcl-2 family. Fluorescence lifetime imaging microscopy (FLIM) is used to detect Förster resonance energy transfer (FRET) between two fluorescent-fusion proteins in live cells. FLIM-FRET has been used to detect specific interactions and their disruption, for Bcl-2 family proteins. To date, this has been possible only in low throughput, due to the time required for serial data acquisition. We developed an automated optical system with eight parallel detectors for rapid and efficient data collection...
2019: Methods in Molecular Biology
Margaret Chern, Joshua C Kays, Shashi Bhuckory, Allison Dennis
Fluorescent sensors benefit from high signal-to-noise and multiple measurement modalities, allowing for a multitude of applications and flexibility of design. Semiconductor nanocrystal quantum dots (QDs) are excellent fluorophores for sensors because of their extraordinary optical properties. They have high thermal and photochemical stability compared to organic dyes or fluorescent proteins and are extremely bright due to their large molar cross-sections. In contrast to organic dyes, QD emission profiles are symmetric, with relatively low full width half maxima...
December 7, 2018: Methods and Applications in Fluorescence
Graham Hungerford, M Adília Lemos, Boon-Seang Chu
The binding of an extract from the flowers of Clitoria ternatea L. to the digestive enzyme α-amylase was investigated. This extract is a mixture of flavonoids, including anthocyanins, and has been previously shown to inhibit the activity this enzyme. This has implications for modulating starch digestion. In order to investigate the kinetics, we made use of time-resolved fluorescence to simultaneously monitor two different emission bands emanating from the extract. This measurement was enabled by the use of a "photon streaming" approach and changes in fluorescence lifetime and intensity were used to follow the interaction...
November 30, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
J A Lebrón, F J Ostos, M López-López, M L Moyá, O Kardell, A Sánchez, C J Carrasco, M García-Calderón, C B García-Calderón, I V Rosado, P López-Cornejo
The use of nanovectors in several medicinal treatments has reached a great importance in the last decade. Some drugs need to be protected to increase their lifetimes in the blood flow, to avoid degradation, to be delivered into target cells or to decrease their side effects. The goal of this work was to design and prepare nanovectors formed by novel surfactants derived from the [Ru(bpy)3 ]2+ complex. These amphiphilic molecules are assembled to form metallomicelles which can act as pharmaceutical agents and, at the same time, as nanovectors for several drugs...
November 29, 2018: Colloids and Surfaces. B, Biointerfaces
Zece Zhu, Di Tian, Pengli Gao, Ke Wang, Yuce Li, Xuewen Shu, Jintao Zhu, Qiang Zhao
Luminescent probes and nanoparticles (NPs) with long excited state lifetimes are essential for time-resolved biological imaging. Generally, cell membranes are physiological barriers that could prevent the uptake of many unnatural compounds. It is still a big challenge to prepare biocompatible imaging agents with high cytomembrane permeability, especially for nonmetallic NPs with long-lived luminescence. Herein, an amphiphilic cell-penetrating peptide, F6 G6 (rR)3 R2 , was designed to transport hydrophobic fluorophores across cellular barriers...
December 10, 2018: Journal of the American Chemical Society
Minghan Cai, Dongdong Zhang, Jingyi Xu, Xiangchen Hong, Chongguang Zhao, Xiaozeng Song, Yong Qiu, Hironori Kaji, Lian Duan
Recent researches on noble-metal-free thermally activated delayed fluorescent (TADF) materials have boosted the efficiencies of organic light-emitting diodes (OLEDs) to unity. However, short lifespan still hinders their further practical application. Carrier recombination pathways have been reported to have significant influence on efficiencies of TADF devices, though their effects on device lifetimes remain rarely studied. Here, we have designed and synthesized five pyrimidine or pyrazine/carbazole isomers as hosts for TADF OLEDs to explore the inherent role of Langevin recombination (LR) and trap assisted recombination (TAR) on device lifetimes...
December 10, 2018: ACS Applied Materials & Interfaces
Yufen Yuan, Yuxiao Han, Bo Huang, Lei Zhang, Hongyu Yang, Bing Gu, Yiping Cui, Jiayu Zhang
In an ultraviolet detection system, the Si-based photodetector could be sensitized with some kinds of fluorescent materials to enhance its response in the short-wavelength range. Thick-shell ZnCdS:Mn/ZnS core/shell quantum dots (QDs) exhibit unique advantage in UV signal sensitization due to their long PL lifetime, as well as stable emission matched with CCD's response. Herein, a single-channel UV panoramic detection system based on these Mn-doped QDs has been proposed. The QDs film was attached onto a Si-based CCD versus a tapered fiber, and an optical chopper was mounted before the QDs film...
November 26, 2018: Nanotechnology
Stefan Fischer, Tim Pier, Thomas Jüstel
This work deals with the photoluminescence of various composite structured Ca2LuHf2Al3O12 garnet type LED phosphors. It is well known that sensitization of Eu3+ with Ce3+ suffers from metal-to-metal charge transfer (MMCT) quenching. Spatial separation of the sensitizer and activator results in a reduced quenching mechanism and thus higher luminescence intensities, when Ce3+ is excited in the blue spectral range and transfers its energy to Eu3+. The phosphor particles were prepared via different synthesis techniques...
December 5, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Alok Kumar Tripathi, Sushma Kundu, Ranjan Das
Charge-transfer (CT) electronic states are generally seen in molecules involving interactions between species of low ionization potential and high electron affinity. In this context, the 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) free radical is not considered to be a typical molecule to form charge transfer states with aromatic hydrocarbons. Nevertheless, involvement of such CT states has been invoked in rationalising the spin-dependent photophysical quenching of excited states of aromatic systems by TEMPO during bimolecular collisions...
December 5, 2018: Physical Chemistry Chemical Physics: PCCP
Zhiheng Wang, Shi-Jian Su
The progress of white organic light-emitting diodes (WOLEDs) via adopting fluorescent and phosphorescent organic materials have attracted commercial interest for their broad range of visible spectrum and potential of 100 % internal quantum efficiency. In this account, smart molecular designs for developing efficient phosphorescent host and good color purity blue fluorescent emitters are prepared to be discussed, especially donor-acceptor modification to regulate their triplet states and bipolar transport properties...
December 4, 2018: Chemical Record: An Official Publication of the Chemical Society of Japan ... [et Al.]
Julia Prei Szlig, Daniel Kage, Katrin Hoffmann, Todd J Martínez, Ute Resch-Genger, Martin Presselt
The fluorescence lifetime is a key property of fluorophores that can be utilized for microenvironment probing, analyte sensing, and multiplexing as well as barcoding applications. For the rational design of lifetime probes and barcodes, theoretical methods have been developed to enable the ab initio prediction of this parameter, which depends strongly on interactions with solvent molecules and other chemical species in the emitter´s immediate environment. In this work, we investigate how a conductor-like screening model (COSMO) can account for variations in fluorescence lifetimes that are caused by such fluorophore-solvent interactions...
December 3, 2018: Journal of Physical Chemistry. A
Meng Lu, Neil Williamson, Ajay Mishra, Claire H Michel, Clemens F Kaminski, Alan Tunnacliffe, Gabriele S Kaminski Schierle
The 42-amino-acid amyloid-β (Aβ42) is a critical causative agent in the pathology of Alzheimer's disease. The hereditary Arctic mutation of Aβ42 (E22G) leads to increased intracellular accumulation of amyloid-β in early-onset AD. However, it remains largely unknown how the Arctic mutant variant leads to aggressive protein aggregation and increased intracellular toxicity. Here, we constructed stable cell lines expressing fluorescent-tagged wild-type (WT) and E22G Aβ42 to study the aggregation kinetics of the Arctic Aβ42 mutant peptide and its heterogeneous structural forms...
November 30, 2018: Journal of Biological Chemistry
Jaime Gómez-Morales, Cristóbal Verdugo-Escamilla, Raquel Fernández-Penas, Carmen Maria Parra-Milla, Christophe Drouet, Michele Iafisco, Francesca Oltolina, Maria Prat, Jorge Fernando Fernández-Sánchez
Biocompatible nanosystems exhibiting long-lifetime (∼millisecond) luminescence features are particularly relevant in the field of bioimaging. In this study, citrate-functionalized calcium-doped europium phosphates nanophosphors of the rhabdophane type were prepared at different synthesis times by a bioinspired crystallization route, consisting in thermal decomplexing of Ca2+ /Eu3+ /citrate/phosphate/carbonate solutions. The general formula of this material is Caα Eu1-α (PO4 )1-α (HPO4 )α ·nH2 O, with α ranging from 0 to 0...
November 23, 2018: Journal of Colloid and Interface Science
Michael Saaranen, Dinesh Wagle, Emma McLaughlin, Amelia Paladino, Seth Ashman, S Burc In Bayram
We report on the lifetime measurement of the <mml:math xmlns:mml=""> <mml:mn>6</mml:mn> <mml:msup> <mml:mrow> <mml:mtext> </mml:mtext> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:msubsup> <mml:mrow> <mml:mi>Σ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> <mml:mrow> <mml:mo>(</mml:mo> <mml:mrow> <mml:mn>7,31</mml:mn> </mml:mrow> <mml:mo>)</mml:mo> </mml:mrow> </mml:math> state of Na2 molecules, produced in a heat-pipe oven, using a time-resolved spectroscopic technique...
November 28, 2018: Journal of Chemical Physics
Romain Letrun, Bernhard Lang, Oleksandr Yushchenko, Roland Wilcken, Denis Svechkarev, Dmytro Kolodieznyi, Eberhard Riedle, Eric Vauthey
The excited-state dynamics of a T-shaped bichromophoric molecule, consisting of two strong fluorophores, diphenyloxazole and diphenylpyrazoline, directly linked in an orthogonal geometry, was investigated. Despite the weak coupling ensured by this geometry and confirmed by the electronic absorption spectra, this dyad exhibits only weak fluorescence in both apolar and polar solvents, with fluorescence lifetimes ranging from 200 ps in CHX to 10 ps in ACN. Ultrafast spectroscopic measurements reveal that the fluorescence quenching in polar solvents is due to the population of a charge-separated state...
November 29, 2018: Physical Chemistry Chemical Physics: PCCP
Arshdeep Sidhu, Jonathan Vaneyck, Christian Blum, Ine Segers-Nolten, Vinod Subramaniam
Thioflavin-T (ThT) is the most commonly used fluorescent dye for following amyloid formation semi-quantitatively in vitro, specifically probing the fibrillar cross-β-sheet content. In recent years, structural polymorphism of amyloid fibrils has been shown to be an important aspect of amyloid formation, both in vitro and in neurodegenerative diseases. Therefore, understanding ThT-amyloid interactions in the context of structural polymorphism of amyloids is necessary for correct interpretation of ThT fluorescence data...
September 2018: Amyloid: the International Journal of Experimental and Clinical Investigation
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