scholarly journals Flipping the switch: reverse-demand voltage-sensitive fluorophores

2021 ◽  
Author(s):  
Jack McCann ◽  
Brittany Benlian ◽  
Isaac Knudson ◽  
Evan Miller
Keyword(s):  
Excited State ◽  
Electron Flow ◽  
Biological Membrane ◽  
Molecular Wires ◽  
Opposite Polarity ◽  
Membrane Potentials ◽  
Living Systems ◽  
Voltage Sensitivity ◽  
Fluorescence Sensing ◽  
Biological Environment

Fluorescence microscopy with fluorescent reporters that respond to environmental cues are a powerful method for interrogating biochemistry and biophysics in living systems. Photoinduced electron transfer (PeT) is commonly used as a trigger to modulate fluorescence in response to changes in the biological environment. PeT based indicators rely either on PeT into the excited state (acceptor PeT) or out of the excited state (donor PeT). Our group has been developing voltage-sensitive fluorophores (VF dyes) that respond to changes in biological membrane potential. We hypothesize that the mechanism of voltage sensitivity arises from acceptor PeT (a-PeT) from an electron-rich aniline-containing molecular wire into the excited state fluorophore, resulting in decreased fluorescence at negative membrane potentials. Here, we can reverse the direction of electron flow to access donor-excited PeT (d-PeT) VF dyes by introducing electron-withdrawing (EWG), rather than electron-rich molecular wires. Similar to first-generation aniline containing VF dyes, EWG-containing VF dyes show voltage-sensitive fluorescence, but with the opposite polarity: hyperpolarizing membrane potentials now give fluorescence increases. We use a combination of computation and experiment to estimate a ΔE of ~0.6 eV for voltage sensitivity in d-PeT indicators, show that two of the new reverse VF dyes are voltage sensitive, and provide the first example, to our knowledge, of a molecular sensor that can be tuned across energy regimes to access bi-directional electron flow for fluorescence sensing in living systems.

Symmetrical and unsymmetrical thiazole-based ESIPT derivatives: the highly selective fluorescence sensing of Cu2+ and structure-controlled reversible mechanofluorochromism

CrystEngComm ◽  
2021 ◽  
Vol 23 (38) ◽  
pp. 6769-6777
Author(s):  
Parthasarathy Gayathri ◽  
Karuppaiah Kanagajothi ◽  
Probal Nag ◽  
Neethu Anand ◽  
Vennapusa Sivaranjana Reddy ◽  
...  
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Intramolecular Proton Transfer ◽  
Fluorescence Sensing ◽  
Light Emitting ◽  
Organic Fluorophores

Excited state intramolecular proton transfer (ESIPT) process-based organic fluorophores provide an opportunity to develop large Stokes-shifted multifunctional fluorescence systems for light emitting, chemosensing and bioimaging applications.

scholarly journals Ingenious modification of molecular structure effectively regulates excited-state intramolecular proton and charge transfer: a theoretical study based on 3-hydroxyflavone

RSC Advances ◽  
2018 ◽  
Vol 8 (52) ◽  
pp. 29589-29597 ◽  
Author(s):  
Jianhui Han ◽  
Xiaochun Liu ◽  
Chaofan Sun ◽  
You Li ◽  
Hang Yin ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Excited State ◽  
Charge Transfer ◽  
Proton Transfer ◽  
Theoretical Study ◽  
Intramolecular Charge Transfer ◽  
Intramolecular Proton Transfer ◽  
Great Promise ◽  
Fluorescence Sensing

Harnessing ingenious modification of molecular structure to regulate excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) characteristics holds great promise in fluorescence sensing and imaging.

Conductance changes underlying a late synaptic hyperpolarization in hippocampal CA3 neurons

1987 ◽  
Vol 58 (1) ◽  
pp. 160-179 ◽  
Author(s):  
J. J. Hablitz ◽  
R. H. Thalmann
Keyword(s):  
Membrane Potential ◽  
Voltage Clamp ◽  
Time Course ◽  
Membrane Potentials ◽  
Resting Membrane Potential ◽  
Extracellular Potassium ◽  
Voltage Sensitivity ◽  
Base Line ◽  
Membrane Hyperpolarization ◽  
Ca3 Neurons

1. Single-electrode current- and voltage-clamp techniques were employed to study properties of the conductance underlying an orthodromically evoked late synaptic hyperpolarization or late inhibitory postsynaptic potential (IPSP) in CA3 pyramidal neurons in the rat hippocampal slice preparation. 2. Late IPSPs could occur without preceding excitatory postsynaptic potentials at the resting membrane potential and were graded according to the strength of the orthodromic stimulus. The membrane hyperpolarization associated with the late IPSP peaked within 140-200 ms after orthodromic stimulation of mossy fiber afferents. The late IPSP returned to base line with a half-decay time of approximately 200 ms. 3. As determined from constant-amplitude hyperpolarizing-current pulses, the membrane conductance increase during the late IPSP, and the time course of its decay, were similar whether measurements were made near the resting membrane potential or when the cell was hyperpolarized by approximately 35 mV. 4. When 1 mM cesium was added to the extracellular medium to reduce inward rectification, late IPSPs could be examined over a range of membrane potentials from -60 to -140 mV. For any given neuron, the late IPSP amplitude-membrane potential relationship was linear over the same range of membrane potentials for which the slope input resistance was constant. The late IPSP reversed symmetrically near -95 mV. 5. Intracellular injection of ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid or extracellular application of forskolin, procedures known to reduce or block certain calcium-dependent potassium conductances in CA3 neurons, had no significant effect on the late IPSP. 6. Single-electrode voltage-clamp techniques were used to analyze the time course and voltage sensitivity of the current underlying the late IPSP. This current [the late inhibitory postsynaptic current (IPSC)] began as early as 25 ms after orthodromic stimulation and reached a peak 120-150 ms following stimulation. 7. The late IPSC decayed with a single exponential time course (tau = 185 ms). 8. A clear reversal of the late IPSC at approximately -99 mV was observed in a physiological concentration of extracellular potassium (3.5 mM).(ABSTRACT TRUNCATED AT 400 WORDS)

Theoretical rationalisation of the photophysics of a TICT excited state of cinnamoyl–coumarin derivatives in homogeneous and biological membrane models

2018 ◽  
Vol 20 (43) ◽  
pp. 27621-27629 ◽  
Author(s):  
Daniel Zúñiga-Núñez ◽  
Ricardo A. Zamora ◽  
Pablo Barrias ◽  
Cristian Tirapegui ◽  
Horacio Poblete ◽  
...  
Keyword(s):  
Excited State ◽  
Potential Energy ◽  
Structural Dynamics ◽  
Biological Membrane ◽  
Coumarin Derivatives ◽  
Energy Barriers ◽  
Membrane Models

Analysis of the potential energy barriers and structural dynamics of a new TICT-probe for monitoring biological environments.

Molecular Wires Based on Thienylethynylene:  Synthesis, Photophysical Properties, and Excited-State Lifetime

2008 ◽  
Vol 10 (1) ◽  
pp. 17-20 ◽  
Author(s):  
Jin-Liang Wang ◽  
Zheng-Ming Tang ◽  
Qi Xiao ◽  
Qi-Feng Zhou ◽  
Yuguo Ma ◽  
...  
Keyword(s):  
Excited State ◽  
Photophysical Properties ◽  
Molecular Wires ◽  
Excited State Lifetime

Impact of Vibrations and Electronic Coherence on Electron Transfer in Flat Molecular Wires

MRS Advances ◽  
2017 ◽  
Vol 2 (14) ◽  
pp. 811-816 ◽  
Author(s):  
Oscar Grånäs ◽  
Grigory Kolesov ◽  
Efthimios Kaxiras
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Real Time ◽  
Density Functional ◽  
Molecular Wires ◽  
The Real ◽  
Velocity Autocorrelation ◽  
Td Dft ◽  
Electronic Coherence ◽  
The Impact

ABSTRACTElectron transfer in molecular wires are of fundamental importance for a range of optoelectronic applications. The impact of electronic coherence and ionic vibrations on transmittance are of great importance to determine the mechanisms, and subsequently the type of wires that are most promising for applications. In this work, we use the real-time formulation of time-dependent density functional theory to study electron transfer through oligo-p-phenylenevinylene (OPV) and the recently synthesized carbon bridged counterpart (COPV). A system prototypical of organic photovoltaics is setup by bridging a porphyrin-fullerene dyad, allowing a photo-excited electron to flow between the Zn-porphyrin (ZnP) chromophore and the C60 electron acceptor through the molecular wire. The excited state is described using the fully self-consistent ∆-SCF method. The state is then propagated in time using the real-time TD-DFT scheme, while describing ionic vibrations with classical nuclei. The charge transferred between porphyrin and C60 is calculated and correlated with the velocity autocorrelation functions of the ions. This provides a microscopic insight to vibrational and tunneling contributions to electron transport in linked porphyrin-fullerene dyads. We elaborate on important details in describing the excited state and trajectory sampling.

Application of Atomic Absorption in the Study of Na, K, Mg, and Ca Binding by Cellular Membranes

1966 ◽  
Vol 20 (3) ◽  
pp. 135-141 ◽  
Author(s):  
Hisashi Sanui ◽  
Nello Pace
Keyword(s):  
Atomic Absorption ◽  
Biological Membrane ◽  
Inorganic Ions ◽  
Atomic Absorption Spectrophotometry ◽  
Living Systems ◽  
Single Sample ◽  
Membrane Material ◽  
Membrane Materials ◽  
Absorption Spectrophotometry ◽  
Sensitive Tool

Atomic-absorption spectrophotometry is applied in the analysis of biological membrane materials for micromolar levels of the physiologically important cations, Na, K, Mg, and Ca. Instrumental parameters and chemical interferences are investigated and a method for the measurement of all four cations in a single sample of ashed membrane material is formulated, tested, and applied. Results are highly satisfactory, and demonstrate that atomic-absorption spectrophotometry affords biologists a powerful and sensitive tool for the study of the important rôle played by inorganic ions in living systems.

scholarly journals Insights into Characterization Methods and Biomedical Applications of Nanoparticle–Protein Corona

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3093
Author(s):  
Yan Li ◽  
Jae-Seung Lee
Keyword(s):  
Biomedical Applications ◽  
Protein Corona ◽  
Living Systems ◽  
Future Perspectives ◽  
Research Attention ◽  
Characterization Methods ◽  
Biological Environment ◽  
Biological Milieu

Nanoparticles (NPs) exposed to a biological milieu will strongly interact with proteins, forming “coronas” on the surfaces of the NPs. The protein coronas (PCs) affect the properties of the NPs and provide a new biological identity to the particles in the biological environment. The characterization of NP-PC complexes has attracted enormous research attention, owing to the crucial effects of the properties of an NP-PC on its interactions with living systems, as well as the diverse applications of NP-PC complexes. The analysis of NP-PC complexes without a well-considered approach will inevitably lead to misunderstandings and inappropriate applications of NPs. This review introduces methods for the characterization of NP-PC complexes and investigates their recent applications in biomedicine. Furthermore, the review evaluates these characterization methods based on comprehensive critical views and provides future perspectives regarding the applications of NP-PC complexes.

scholarly journals Vinyl-fluorene Molecular Wires for Voltage Imaging with Enhanced Sensitivity and Reduced Phototoxicity

2021 ◽  
Author(s):  
Steven Boggess ◽  
Shivaani Gandhi ◽  
Evan Miller
Keyword(s):  
Induced Pluripotent Stem Cell ◽  
Molecular Wires ◽  
Attractive Alternative ◽  
Voltage Sensitivity ◽  
Molecular Wire ◽  
Voltage Imaging ◽  
Enhanced Sensitivity ◽  
Induced Pluripotent ◽  
Low Sensitivity ◽  
Voltage Sensing Domain

<p>Fluorescent voltage indicators are an attractive alternative for studying the electrical activity of excitable cells; however, the development of indicators that are both highly sensitive and low in toxicity over long-term experiments remains a challenge. Previously, we reported a fluorene-based voltage-sensitive fluorophore that exhibits much lower phototoxicity than previous voltage indicators in cardiomyocyte monolayers, but suffers from low sensitivity to membrane potential changes. Here, we report that the addition of a single vinyl spacer in the fluorene molecular wire scaffold improves the voltage sensitivity 1.5- to 3.5-fold over fluorene-based voltage probes. Furthermore, we demonstrate the improved ability of the new vinyl-fluorene VoltageFluors (v-fVFs) to monitor action potential kinetics in both mammalian neurons and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Addition of the vinyl spacer between the aniline donor and fluorene monomer results in indicators that are significantly less phototoxic in cardiomyocyte monolayers. These results demonstrate how structural modification to the voltage sensing domain have a large effect on improving the overall properties of molecular wire-based voltage indicators. </p>

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