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Fluorescence Lifetime

Sourav Das, Santanu Santra, Mostofa Ataur Rohman, Mahuah Ray, Madhurima Jana, Atanu Singha Roy
The interaction of 6-Hydroxyflavone (6HF) with hen egg white lysozyme (HEWL) has been executed using multi-spectroscopic and computational methods. Steady state fluorescence studies indicated that static quenching mechanism is involved in the binding of 6HF with HEWL, which was further supported by excited state lifetime and UV-vis absorption studies. The binding constant (Kb ) of the HEWL-6HF complex was observed to be 6.44±0.09 ×104 M-1 at 293 K, which decreases with the increase in temperature. The calculation of the thermodynamic quantities showed that the binding is exothermic in nature with a negative enthalpy change (ΔH= -11...
October 12, 2018: Journal of Biomolecular Structure & Dynamics
Zhenxing Qin, Wenhai Wang, Xiaozhi Zhan, Xiujuan Du, Qingmei Zhang, Rui Zhang, Kun Li, Jinhong Li, Weiping Xu
Luminescent carbon-based nanoparticles, named often as carbon dots (CDs), were synthesized from citric acid (CA) and guanidine thiocyanate (GITC) via an N and S co-doped hydrothermal procedure. In the present structure characterization, N and S elements could be sufficiently doped by means of the heteroatom or the functional groups bonded on the surface of CDs. The as-prepared CDs solution showed blue color fluorescence under ultraviolet excitation, yet the PL spectra exhibited a repetitive emission process from excitation-independent to excitation-dependent...
October 4, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Micaela E Grassano, Marcela S Altamirano, M Paula Militello, Ernesto M Arbeloa, Carlos M Previtali, Sonia G Bertolotti
The photophysical and photochemical properties of the xanthene dyes mercurochrome (MCr) and eosin-Y (Eos); and the phenazine dye safranine-O (SF) are evaluated in the presence of amino-terminated polyamidoamine (PAMAM) dendrimers of low generations. The dendrimers produce a red shift in the UV-vis absorption spectra of the dyes, which increases with concentration and the size of the PAMAM molecule. The Stern-Volmer plots of fluorescence quenching for xanthenic dyes present a downward curvature. It is ascribed to a static mechanism involving a dye-dendrimer binding...
October 12, 2018: Photochemistry and Photobiology
Aparna Dravid U, Nirmal Mazumder
A cancerous cell is characterized by morphological and metabolic changes which are the key features of carcinogenesis. Adenosine triphosphate (ATP) in cancer cells is primarily produced by aerobic glycolysis rather than oxidative phosphorylation. In normal cellular metabolism, nicotinamide adenine dinucleotide (NADH) is considered as a principle electron donor and flavin adenine dinucleotide (FAD) as an electron acceptor. During metabolism in a cancerous cell, a net increase in NADH is found as the pathway switched from oxidative phosphorylation to aerobic glycolysis...
October 11, 2018: Lasers in Medical Science
Victoriya Kim, Lukasz Piatkowski, Maria Pszona, Regina Jäger, Jakub Ostapko, Jerzy Sepioł, Alfred J Meixner, Jacek Waluk
Parent hemiporphycene, a recently obtained constitutional isomer of porphyrin, exists in room temperature solutions and polymer matrices in the form of two trans tautomers interconverting via double hydrogen transfer. Using confocal fluorescence microscopy, it was possible to monitor tautomerization in single hemiporphycene molecules embedded in a PMMA film by monitoring the spectral and temporal evolution of their fluorescence spectra. The emission spectra of the two tautomeric forms are similar to those obtained from ensemble studies...
October 12, 2018: Physical Chemistry Chemical Physics: PCCP
Christoph Kerzig, Oliver S Wenger
Sensitized triplet-triplet annihilation (TTA) is a promising mechanism for solar energy conversion, but so far its application has been practically completely limited to organic solvents and self-assembled or solid state systems. Combining water-soluble ruthenium complex-pyrene dyads with particularly long excited-state lifetimes as sensitizers and highly fluorescent commercial anthracenes as acceptors/annihilators, we were able to achieve green-to-violet upconversion with unprecedented quantum yields in pure water...
August 28, 2018: Chemical Science
Pia Hansson, Helen Boyd, Ian L Dale, Göran Dahl, Felix Nicolaus, Wayne Bowen, Klaus Doering, Colin Dunsmore, Graham Cotton, Helena Lindmark
Fluorescence assay technologies are commonly used in high-throughput screening because of their sensitivity and ease of use. Different technologies have their characteristics and the rationale for choosing one over the other can differ between projects because of factors such as availability of reagents, assay performance, and cost. Another important factor to consider is the assay susceptibility to artifacts, which is almost as important as the ability of the assay to pick up active compounds. Spending time and money on false positives or missing the opportunity to build chemistry around false negatives is something that every drug project tries to avoid...
October 9, 2018: Assay and Drug Development Technologies
Rozhin Penjweini, Alessio Andreoni, Tilman Rosales, Jeonghan Kim, Michael D Brenner, Dan L Sackett, Jay H Chung, Jay R Knutson
Oxygen (O2) is one of the most important biometabolites. In abundance, it serves as the limiting terminus of aerobic respiratory chains in the mitochondria of higher organisms; in deficit, it is a potent determinant of development and regulation of other physiological and therapeutic processes. Most knowledge on intracellular and interstitial concentration ([O2]) is derived from mitochondria isolated from cells or tissue biopsies, providing detailed but nonnative insight into respiratory chain function. The possible loss of essential metabolites during isolation and disruption of the normal interactions of the organelle with the cytoskeleton may cause these data to misrepresent intact cells...
October 2018: Journal of Biomedical Optics
Qianwen Liu, Mengdi Wang, Yishan He, Xuxu Wang, Wenyue Su
A series of amorphous Co-P alloy modified ZnIn2S4 composite samples were synthesized through a one-step photochemical method. The as-prepared samples were systematically characterized and the photocatalytic activity for H2 production under visible-light irradiation was investigated. It was found that the Co-P/ZnIn2S4 composite samples exhibited higher photocatalytic activity, which is 44 times higher than that of pure ZnIn2S4 and higher than that of the 1 wt% Pt/ZnIn2S4 sample. After modifying with amorphous Co-P alloy, the composite samples showed enhanced photocurrent, reduced photoelectric impedance, weakened fluorescence intensity and extended fluorescence lifetime, which accelerate the separation and transfer of photoinduced charge effectively, thus improving the catalytic activity of the composite sample...
October 9, 2018: Nanoscale
Jenu V Chacko, Kevin W Eliceiri
Autofluorescence imaging (AFI) has greatly accelerated in the last decade, way past its origins in detecting endogenous signals in biological tissues to identify differences between samples. There are many endogenous fluorescence sources of contrast but the most robust and widely utilized have been those associated with metabolism. The intrinsically fluorescent metabolic cofactors nicotinamide adenine dinucleotide (NAD+ /NADH) and flavin adenine dinucleotide (FAD/FADH2 ) have been utilized in a number of AFI applications including basic research, clinical, and pharmaceutical studies...
October 8, 2018: Cytometry. Part A: the Journal of the International Society for Analytical Cytology
Carlos Castillam, Martin Maskam, Dmitry V Sorokin, Erik Meijering, Carlos Ortiz-de-Solorzano
We present a three-dimensional bioimage analysis workflow to quantitatively analyze single, actin-stained cells with filopodial protrusions of diverse structural and temporal attributes, such as number, length, thickness, level of branching, and lifetime, in time-lapse confocal microscopy image data. Our workflow makes use of convolutional neural networks trained using real as well as synthetic image data, to segment the cell volumes with highly heterogeneous fluorescence intensity levels and to detect individual filopodial protrusions, followed by a constrained nearest-neighbor tracking algorithm to obtain valuable information about the spatio-temporal evolution of individual filopodia...
October 5, 2018: IEEE Transactions on Medical Imaging
Suman Ranjit, Leonel Malacrida, Enrico Gratton
The phasor approach to FLIM (Fluorescence Lifetime Imaging Microscopy) is becoming popular due to the powerful fit free analysis and the visualization of the decay at each point in images of cells and tissues. However, although several implementation of the method are offered by manufactures of FLIM accessories for microscopes, the details of the conversion of the decay to phasors at each point in an image requires some consideration. Here, we show that if the decay is not properly acquired, the apparently simple phasor transformation can provide incorrect phasor plots and the results may be misinterpreted...
October 8, 2018: Microscopy Research and Technique
Fanny Poulon, Johan Pallud, Pascale Varlet, Marc Zanello, Fabrice Chretien, Edouard Dezamis, Georges Abi-Lahoud, François Nataf, Baris Turak, Bertrand Devaux, Darine Abi Haidar
The primary line of therapy for high-grade brain tumor is surgical resection, however, identifying tumor margins in vivo remains a major challenge. Despite the progress in computer-assisted imaging techniques, biopsy analysis remains the standard diagnostic tool when it comes to delineating tumor margins. Our group aims to answer this challenge by exploiting optical imaging of endogenous fluorescence in order to provide a reliable and reproducible diagnosis close to neuropathology. In this study, we first establish the ability of two-photon microscopy (TPM) to discriminate normal brain tissue from glioblastomas and brain metastasis using the endogenous fluorescence response of fresh human brain sample...
October 5, 2018: Scientific Reports
Shuting Pang, Miriam Más-Montoya, Manjun Xiao, Chunhui Duan, Zhenfeng Wang, Xi Liu, Rene Janssen, Gang Yu, Fei Huang, Yong Cao
The packing mode of small molecular semiconductors in thin films is an important factor that controls the performance of their optoelectronic devices. Designing and changing the packing mode via molecular engineering is challenging. Three structurally-related diketopyrrolopyrrole (DPP) based molecules are synthesized to study the effect of replacing C-C bonds by isoelectronic dipolar B←N bonds. By replacing one of the bridging C-C bonds on the peripheral fluorene units of the DPP molecules by a coordinative B←N bond and changing the B←N bond orientation, the optical absorption, fluorescence, and excited state lifetime of the molecules can be tuned...
October 4, 2018: Chemistry: a European Journal
J Dalla Rizza, L M Randall, J Santos, G Ferrer-Sueta, A Denicola
Peroxiredoxins are thiol-dependent peroxidases that function in peroxide detoxification and H2 O2 induced signaling. Among the six isoforms expressed in humans, PRDX1 and PRDX2 share 97% sequence similarity, 77% sequence identity including the active site, subcellular localization (cytosolic) but they hold different biological functions albeit associated with their peroxidase activity. Using recombinant human PRDX1 and PRDX2 the kinetics of oxidation and hyperoxidation with H2 O2 and peroxynitrite were followed by intrinsic fluorescence...
October 3, 2018: Protein Science: a Publication of the Protein Society
Jun-Cheng Zhang, Cong Pan, Yi-Fei Zhu, Li-Zhen Zhao, Hong-Wei He, Xiaofeng Liu, Jianrong Qiu
Optical characteristics of luminescent materials, including emission color (wavelength), lifetime, and excitation mode, play crucial roles in data communication and information security. Conventional luminescent materials generally display unicolor, unitemporal, and unimodal (occasionally bimodal) emission, resulting in low-level readout and decoding. The development of multicolor, multitemporal, and multimodal luminescence in a single material has long been considered to be a significant challenge. In this study, for the first time, the superior integration of colorful (red-orange-yellow-green), bitemporal (fluorescent and delayed), and four-modal (thermo-/mechano-motivated and upconverted/downshifted) emissions in a particular piezoelectric particle via optical multiplexing of dual-lanthanide dopants is demonstrated...
October 3, 2018: Advanced Materials
Zoran Ristanovic, Abhishek Dutta Chowdhury, Rasmus Brogaard, Klaartje Houben, Marc Baldus, Johan Hofkens, Maarten B J Roeffaers, Bert M Weckhuysen
Zeolite activity and selectivity is often determined by the underlying proton and hydrogen-transfer reaction pathways. For the first time, we use single-molecule fluorescence microscopy to directly follow the real-time behavior of individual styrene-derived carbocationic species formed within zeolite ZSM-5. We find that inter-mittent fluorescence and remarkable photostability of carbocationic intermediates strongly depend on the local chemical environment imposed by zeolite framework and guest solvent molecules...
October 3, 2018: Journal of the American Chemical Society
Frances D Morris, Eric M Peterson, Jennifer M Heemstra, Joel M Harris
Aptamers are short nucleic-acid biopolymers selected to have high affinity and specificity for protein or small-molecule target analytes. Aptamers can be engineered into split-aptamer biosensors comprising two nucleic acid strands that co-assemble as they bind to a target, resulting in a large signal change from attached molecular probes (e.g. molecular beacons). The kinetics of split-aptamer assembly and their dependence on target recognition are largely unknown; knowledge of these kinetics could help in design and optimization of split-aptamer biosensors...
October 3, 2018: Analytical Chemistry
Umit Ay, Sinem Ezgi Sarlı
Inclusion complex of naphthalene with methyl-beta-cyclodextrin in water has been formed. The aqueous solutions of the various amounts of Co2+ ve Mn2+ salts have been added to naphthalene-methyl-beta-cyclodextrin (NAP-Me-β-CD) inclusion complexes. Fluorescence properties of the naphthalene (NAP) compound have been utilized to observe the changes in fluorescence intensities. Stern-Volmer quenching constants and fluorescence quantum yields have been calculated. Characterization of the resulting complex by FT-IR and 1 H NMR technique has been determined...
October 2, 2018: Journal of Fluorescence
Michael J Morten, Sergio G Lopez, I Emilie Steinmark, Aidan Rafferty, Steven W Magennis
From gene expression to nanotechnology, understanding and controlling DNA requires a detailed knowledge of its higher order structure and dynamics. Here we take advantage of the environment-sensitive photoisomerization of cyanine dyes to probe local and global changes in DNA structure. We report that a covalently attached Cy3 dye undergoes strong enhancement of fluorescence intensity and lifetime when stacked in a nick, gap or overhang region in duplex DNA. This is used to probe hybridization dynamics of a DNA hairpin down to the single-molecule level...
October 2, 2018: Nucleic Acids Research
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