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Fluorescence Lifetime

Yaning Cui, Xi Zhang, Meng Yu, Yingfang Zhu, Jingjing Xing, Jinxing Lin
Detecting protein-protein interactions (PPIs) provides fundamental information for understanding biochemical processes such as the transduction of signals from one cellular location to another; however, traditional biochemical techniques cannot provide sufficient spatio-temporal information to elucidate these molecular interactions in living cells. Over the past decade, several new techniques have enabled the identification and characterization of PPIs. In this review, we summarize three main techniques for detecting PPIs in vivo, focusing on their basic principles and applications in biological studies...
March 14, 2019: Science China. Life Sciences
Xiaofeng Li, Bo Li, Jixu Liu, Zhifeng Zhu, Dayuan Zhang, Yifu Tian, Qiang Gao, Zhongshan Li
We demonstrate the enhancement of femtosecond (fs) laser-induced filaments in air and nitrogen flow fields using a nanosecond (ns) laser. With the ns laser being imposed on the filaments, the length and the emission intensity of the filaments were largely increased. Temporally resolved spectra of the enhanced filaments were obtained. The results show that the ns laser enhanced the short-lifetime fluorescence of nitrogen, which comes from the transition processes of N2 + (B2 Σu + - X2 Σg + ), N2 (B3 Пg - A3 Σu + ) and N2 (C3 Пu - B3 Пg )...
February 18, 2019: Optics Express
Maria Rosaria di Nunzio, Ganchimeg Perenlei, Abderrazzak Douhal
Micro- and mesoporous silica-based materials are a class of porous supports that can encapsulate different guest molecules. The formation of these hybrid complexes can be associated with significant alteration of the physico-chemical properties of the guests. Here, we report on a photodynamical study of a push⁻pull molecule, trans -4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), entrapped within faujasite-type zeolites (HY, NaX, and NaY) and MCM-41 in dichloromethane suspensions. The complex formation gives rise to caged monomers and H- and J-aggregates...
March 15, 2019: International Journal of Molecular Sciences
Hendrik Böhnke, Katharina Röttger, Rebecca Ingle, Hugo J B Marroux, Mats Bohnsack, Nina K Schwalb, Andrew J Orr-Ewing, Friedrich Temps
The fluorescent analogue 2-aminopurine (2AP) of the canonical nucleobase adenine (6 aminopurine) base-pairs with thymine (T) without disrupting the helical structure of the DNA. It therefore finds frequent use in molecular biology for probing DNA and RNA structure and conformational dynamics. However, detailed understanding of the processes responsible for fluorescence quenching remains largely elusive on a fundamental level. While attempts have been made to ascribe decreased excited-state lifetimes to intra-strand charge transfer and stacking interactions, possible influences from dynamic inter-strand H-bonding have been widely ignored...
March 15, 2019: Journal of Physical Chemistry. B
Alber Douglawi, Venkat Athmanathan, Mikhail N Slipchenko, James R Gord, Terrence R Meyer
Laser-induced exciplex fluorescence is a well-established technique for liquid-vapor imaging in evaporating sprays that offers phase-dependent spectrally separated emission. However, the accuracy of this approach is limited by substantial crosstalk from the liquid to vapor phase signals. This Letter shows the use of a combination of spectral and temporal filtering to reduce this crosstalk by three orders of magnitude and eliminate the need for temperature-dependent crosstalk corrections in the N,N-diethylmethylamine/fluorobenzene system...
March 15, 2019: Optics Letters
Yu Lu, Gaofeng Feng, Meng Wang, Lei Zhang, Junyong Yang, Junjie Zhang
Tm3+ -doped silica-glass preforms were fabricated by the modified chemical vapor deposition process combined with the solution doping technique. Its spectroscopic properties were evaluated according to the detected absorption spectrum and the fluorescence spectrum. The calculated maximum emission cross section of Tm3+ ions in this core glass is 5.66×10-21   cm2 , and the tested fluorescence lifetime is 544 μs at 1816 nm. According to the theory of Dexter and Forster, the cross-relaxation rate was calculated by the integral overlap of the absorption and emission cross sections...
March 1, 2019: Applied Optics
Paula Dlugosz, Roland Tresky, Johannes Nimpf
The canonical Reelin signaling cascade regulates correct neuronal layering during embryonic brain development. Details of this pathway are still not fully understood since the participating components are highly variable and create a complex mixture of interacting molecules. Reelin is proteolytically processed resulting in five different fragments some of which carrying the binding site for two different but highly homologous receptors, apolipoprotein E receptor 2 (ApoER2) and very low density lipoprotein receptor (VLDLR)...
2019: Frontiers in Molecular Neuroscience
Hongtao Zhang, Eric Linster, Lucy Gannon, Wiebke Leemhuis, Chelsea A Rundle, Frederica L Theodoulou, Markus Wirtz
Targeted protein degradation is an important and pervasive regulatory mechanism in plants, required for perception and response to the environment as well as developmental signalling. Despite the significance of this process, relatively few studies have assessed plant protein turnover in a quantitative fashion. Tandem fluorescent protein timers (tFTs) offer a powerful approach for the assessment of in vivo protein turnover in distinct subcellular compartments of single or multiple cells. A tFT is a fusion of two different fluorescent proteins with distinct fluorophore maturation kinetics, which enable protein age to be estimated from the ratio of fluorescence intensities of the two fluorescent proteins...
March 14, 2019: Plant Physiology
Elina Andresen, Ute Resch-Genger, Michael Schäferling
An emerging class of inorganic optical reporters are near infrared (NIR) excitable lanthanide-based upconversion nano-particles (UCNPs) with multicolor emission and long luminescence lifetimes in the range of several hundred of micro-seconds. For the design of chemical sensors and optical probes that reveal analyte-specific changes in their spectroscopic properties, these nanomaterials must be combined with sensitive indicator dyes that change their absorption and/or fluorescence properties selectively upon the interaction with their target analyte, utilizing either resonance energy trans-fer (RET) processes or reabsorption-related inner filter effects...
March 14, 2019: Langmuir: the ACS Journal of Surfaces and Colloids
Thierry Tran, Antonio Prlj, Kun-Han Lin, Daniel Hollas, Clémence Corminboeuf
A recent implementation of time-dependent tight-binding density functional theory is employed in excited state molecular dynamics for the investigation of the fluorescence quenching mechanism in 3 prototypical aggregation-induced emission systems. An assessment of the accuracy of the electronic structure method is done by comparison with previous theoretical work while dynamics simulations were extended to the condensed phase to obtain excited state lifetimes comparable to experiment. A thorough investigation is done on tetraphenylethylene in order to resolve the on-going debate on the role of specific deactivation mechanisms...
March 14, 2019: Physical Chemistry Chemical Physics: PCCP
Amanda N Oehrlein, Antonio Sanchez-Diaz, Philip C Goff, Miquel Planells, Neil Robertson, David A Blank, Wayne L Gladfelter
Oligothiophene dyes with two to five thiophene units were anchored to oleate-capped, quantum-confined zinc oxide nanocrystals (ZnO NCs) through a cyanoacrylate functional group. While the fluorescence of the bithiophene derivative was too weak for meaningful quenching studies, the fluorescence of the dyes with three, four and five thiophene rings was quenched upon binding to the NCs. Ultrafast pump-probe spectroscopy was used to observe the singlet excited states of the free dyes dissolved in dichloromethane as well as attached to a ZnO NC dispersed in the same solvent...
March 14, 2019: Physical Chemistry Chemical Physics: PCCP
Gabrielis Kundrotas, Vitalijus Karabanovas, Marijus Pleckaitis, Marina Juraleviciute, Simona Steponkiene, Zivile Gudleviciene, Ricardas Rotomskis
BACKGROUND: Human mesenchymal stem cells (MSCs) have drawn much attention in the field of regenerative medicine for their immunomodulatory and anti-inflammatory effects. MSCs possess specific tumor-oriented migration and incorporation highlighting the potential for MSCs to be used as an ideal carrier for anticancer agents. Bone marrow is the main source of MSCs for clinical applications. MSCs tracking in vivo is a critical component of the safety and efficacy evaluation of therapeutic cell products; therefore, cells must be labeled with contrast agents to enable visualization of the MSCs migration in vivo...
March 13, 2019: Journal of Nanobiotechnology
Anna-Lena Cost, Samira Khalaji, Carsten Grashoff
Genetically encoded Förster resonance energy transfer (FRET)-based tension sensors measure piconewton-scale forces across individual molecules in living cells or whole organisms. These biosensors show comparably high FRET efficiencies in the absence of tension, but FRET quickly decreases when forces are applied. In this article, we describe how such biosensors can be generated for a specific protein of interest, and we discuss controls to confirm that the observed differences in FRET efficiency reflect changes in molecular tension...
March 13, 2019: Current Protocols in Cell Biology
Takayuki Ebata, Nobumasa Chaki, Satoru Muramatsu, Yuji Iida, Seiya Kenjo, Yoshiya Inokuchi, Toshifumi Iimori
The S1 electronic state of 7,7,8,8-Tetracyanoquinodimethane (TCNQ) has been investigated by laser induced fluorescence (LIF), dispersed fluorescence (DF) spectroscopy, and lifetime measurement under jet-cooled condition in the gas-phase. The LIF spectrum showed a weak origin band at 412.13 nm (24262 cm-1) with prominent progression and combination bands involving vibrations of 327, 1098, and 2430 cm-1. In addition, very strong bands appeared at ~363.6 nm (3300 cm-1 above the origin). Both the LIF and DF spectra indicate considerable geometric change in the S1 state...
March 13, 2019: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Sandra Burgstaller, Helmut Bischof, Thomas Gensch, Sarah Stryeck, Benjamin Gottschalk, Jeta Ramadani-Muja, Emrah Eroglu, Rene Rost, Sabine Balfanz, Arnd Baumann, Markus Waldeck-Weiermair, Jesse C Hay, Tobias Madl, Wolfgang F Graier, Roland Malli
Distinct subcellular pH levels, especially in lysosomes and endosomes, are essential for the degradation, modification, sorting, accumulation, and secretion of macromolecules. Here, we engineered a novel genetically encoded pH probe by fusing the pH-stable cyan fluorescent protein (FP) variant, mTurquoise2, to the highly pH-sensitive enhanced yellow fluorescent protein, EYFP. This approach yielded a ratiometric biosensor - referred to as pH-Lemon - optimized for live imaging of distinct pH conditions within acidic cellular compartments...
March 13, 2019: ACS Sensors
Eva Schöll, Lukas Hanschke, Lucas Karl Schweickert, Katharina Zeuner, Marcus Reindl, Saimon Filipe Covre da Silva, Thomas Lettner, Rinaldo Trotta, Jonathan Finley, Kai Müller, Armando Rastelli, Valery Zwiller, Klaus Dieter Jöns
Photonic quantum technologies call for scalable quantum light sources that can be integrated, while providing the end user with single and entangled photons on-demand. One promising candidate are strain free GaAs/AlGaAs quantum dots obtained by droplet etching. Such quantum dots exhibit ultra low multi-photon probability and an unprecedented degree of photon pair entanglement. However, different to commonly studied InGaAs/GaAs quantum dots obtained by the Stranski-Krastanow mode, photons with a near-unity indistinguishability from these quantum emitters have proven to be elusive so far...
March 13, 2019: Nano Letters
Fumiya Kobayashi, Ryo Ohtani, Saki Teraoka, Masaki Yoshida, Masako Kato, Yingjie Zhang, Leonard F Lindoy, Shinya Hayami, Masaaki Nakamura
Luminescent ZnII clusters [Zn4 L4 (μ3 -OMe)2 X2 ] (X=SCN (1), Cl (2), Br (3)) and [Zn7 L6 (μ3 -OMe)2 (μ3 -OH)4 ]Y2 (Y=I- (4), ClO4 - (5)), HL=methyl-3-methoxysalicylate, exhibiting blue fluorescence at room temperature (λmax =416≈429 nm, Φem =0.09-0.36) have been synthesised and investigated in detail. In one case the external heavy-atom effect (EHE) arising the presence of iodide counter anions yielded phosphorescence with a long emission lifetime (λmax =520 nm, τ=95.3 ms) at 77 K. Single-crystal X-ray structural analysis and time-dependent density-functional theory (TD-DFT) calculations revealed that their emission origin was attributed to the fluorescence from the singlet ligand-centred (1 LC) excited state, and the phosphorescence observed in 4 was caused by the EHE of counter anions having strong CH-I interactions...
March 12, 2019: Chemistry: a European Journal
Guochen Bao, Zhenyu Liu, Yuxia Luo, Ka-Leung Wong, Peter A Tanner
Herein, we have investigated spectral structure and intensity changes in a bimetallic lanthanide complex comprising La3+ and Eu3+, with the ions coordinated to silent and antenna ligands, when their positions are interchanged. Comparison of the fluorescence decay of a ligand in the presence and absence of La3+ has enabled internal nonradiative decay rates to be determined. The effects upon Eu3+ emission spectra resulting from changes in its environment at a distance of ∼10 Å, and upon changing from the solid state to solution, were also investigated...
March 12, 2019: Dalton Transactions: An International Journal of Inorganic Chemistry
Qian Liu, Elizabeth J Oesterlund, Xiaoke Chi, Justin Pogmore, Brian Leber, David William Andrews
Tumor initiation, progression and resistance to chemotherapy rely on cancer cells bypassing programmed cell death by apoptosis. We report that unlike other pro-apoptotic proteins, Bim contains two distinct binding sites for the anti-apoptotic proteins Bcl-XL and Bcl-2. These include the BH3 sequence shared with other pro-apoptotic proteins and an unexpected sequence located near the Bim carboxyl-terminus (residues 181-192). Using automated Fluorescence Lifetime Imaging Microscopy - Fluorescence Resonance Energy Transfer (FLIM-FRET) we show that the two binding interfaces enable Bim to double-bolt lock Bcl-XL and Bcl-2 in complexes resistant to displacement by BH3-mimetic drugs currently in use or being evaluated for cancer therapy...
March 12, 2019: ELife
Evgenia Dobrinskikh, Saif I Al-Juboori, Uladzimir Shabeka, Julie A Reisz, Connie Zheng, Ahmed I Marwan
BACKGROUND: Understanding inconsistent clinical outcomes in infants with severe congenital diaphragmatic hernia (CDH) after tracheal occlusion (TO) is a crucial step for advancing neonatal care. The objective of this study is to explore the heterogeneous airspace morphometry and the metabolic landscape changes in fetal lungs after TO. METHODS: Fetal lungs on days 1 and 4 after TO were examined using mass spectrometry-based metabolomics, fluorescence lifetime imaging microscopy (FLIM), the number of airspaces, and tissue-to-airspace ratio (TAR)...
March 8, 2019: Journal of Surgical Research
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