Electron Transfer in a Naphthalene Diimide System Studied by Single-Molecule Delayed Fluorescence

2020 ◽  
Vol 73 (8) ◽  
pp. 699
Author(s):  
Rosalind P. Cox ◽  
Saman Sandanayake ◽  
Steven J. Langford ◽  
Toby D. M. Bell
Keyword(s):  
Electron Transfer ◽  
Single Molecule ◽  
Delayed Fluorescence ◽  
Pmma Film ◽  
Time Resolved ◽  
Single Molecule Level ◽  
Film Interpretation ◽  
Fluorescence Measurements ◽  
Naphthalene Diimide ◽  
Prompt And Delayed Fluorescence

Electron transfer (ET) is a key chemical reaction in nature and has been extensively studied in bulk systems, but remains challenging to investigate at the single-molecule level. A previously reported naphthalene diimide (NDI)-based system (Higginbotham et al., Chem. Commun. 2013, 49, 5061–5063) displays delayed fluorescence with good quantum yield (~0.5) and long-lived (nanoseconds) prompt and delayed fluorescence lifetimes, providing an opportunity to interrogate the underlying ET processes in single molecules. Time-resolved single-molecule fluorescence measurements enabled forward and reverse ET rate constants to be calculated for 45 individual molecules embedded in poly(methylmethacrylate) (PMMA) film. Interpretation of the results within the framework of Marcus–Hush theory for ET demonstrates that variation in both the electronic coupling and the driving force for ET is occurring from molecule to molecule within the PMMA film and over time for individual molecules.

scholarly journals Molecular Brightness Approach for FRET Analysis of Donor-Linker-Acceptor Constructs at the Single Molecule Level: A Concept

2021 ◽  
Vol 8 ◽  
Author(s):  
Taryn M. Kay ◽  
Cody P. Aplin ◽  
Rowan Simonet ◽  
Julie Beenken ◽  
Robert C. Miller ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Single Molecule ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Ensemble Averaging ◽  
Time Resolved ◽  
Single Molecule Level ◽  
Fluorescence Measurements ◽  
Averaging Time ◽  
Molecular Brightness

In this report, we have developed a simple approach using single-detector fluorescence autocorrelation spectroscopy (FCS) to investigate the Förster resonance energy transfer (FRET) of genetically encoded, freely diffusing crTC2.1 (mTurquoise2.1–linker–mCitrine) at the single molecule level. We hypothesize that the molecular brightness of the freely diffusing donor (mTurquoise2.1) in the presence of the acceptor (mCitrine) is lower than that of the donor alone due to FRET. To test this hypothesis, the fluorescence fluctuation signal and number of molecules of freely diffusing construct were measured using FCS to calculate the molecular brightness of the donor, excited at 405 nm and detected at 475/50 nm, in the presence and absence of the acceptor. Our results indicate that the molecular brightness of cleaved crTC2.1 in a buffer is larger than that of the intact counterpart under 405-nm excitation. The energy transfer efficiency at the single molecule level is larger and more spread in values as compared with the ensemble-averaging time-resolved fluorescence measurements. In contrast, the molecular brightness of the intact crTC2.1, under 488 nm excitation of the acceptor (531/40 nm detection), is the same or slightly larger than that of the cleaved counterpart. These FCS-FRET measurements on freely diffusing donor-acceptor pairs are independent of the precise time constants associated with autocorrelation curves due to the presence of potential photophysical processes. Ultimately, when used in living cells, the proposed approach would only require a low expression level of these genetically encoded constructs, helping to limit potential interference with the cell machinery.

scholarly journals Single occupancy spectroelectrochemistry of freely diffusing flavin mononucleotide in zero-dimensional nanophotonic structures

2015 ◽  
Vol 184 ◽  
pp. 101-115 ◽  
Author(s):  
Lawrence P. Zaino ◽  
Dane A. Grismer ◽  
Donghoon Han ◽  
Garrison M. Crouch ◽  
Paul W. Bohn
Keyword(s):  
Electron Transfer ◽  
Single Molecule ◽  
Light Emission ◽  
Fluorescence Emission ◽  
Flavin Mononucleotide ◽  
Wide Field ◽  
Potential Sweep ◽  
Potential Control ◽  
Fluorescence Measurements ◽  
Electron Transfer Properties

Zero-mode waveguides (ZMW) have the potential to be powerful confinement tools for studying electron transfer dynamics at single molecule occupancy conditions. Flavin mononucleotide contains an isoalloxazine chromophore, which is fluorescent in the oxidized state (FMN) while the reduced state (FMNH2) exhibits dramatically lower light emission, i.e. a dark-state. This allows fluorescence emission to report the redox state of single FMN molecules, an observation that has been used previously to study single electron transfer events in surface-immobilized flavins and flavoenzymes, e.g. sarcosine oxidase, by direct wide-field imaging of ZMW arrays. Single molecule electron transfer dynamics have now been extended to the study of freely diffusing molecules using fluorescence measurements of Au ZMWs under single occupancy conditions. The Au in the ZMW serves both as an optical cladding layer and as the working electrode for potential control, thereby accessing single molecule electron transfer dynamics at μM concentrations. Consistent with expectations, the probability of observing single reduced molecules increases as the potential is scanned negative, Eappl < Eeq, and the probability of observing emitting oxidized molecules increases at Eappl > Eeq. Different single molecules exhibit different electron transfer properties as reflected in the position of Eeq and the distribution of Eeq among a population of FMN molecules. Two types of actively-controlled electroluminescence experiments were used: chronofluorometry experiments, in which the potential is alternately stepped between oxidizing and reducing potentials, and cyclic potential sweep fluorescence experiments, analogous to cyclic voltammetry, these latter experiments exhibiting a dramatic scan rate dependence with the slowest scan rates showing distinct intermediate states that are stable over a range of potentials. These states are assigned to flavosemiquinone species that are stabilized in the special environment of the ZMW nanopore.

Reversible Intramolecular Electron Transfer at the Single-Molecule Level

2003 ◽  
Vol 115 (35) ◽  
pp. 4341-4346 ◽  
Author(s):  
Roel Gronheid ◽  
Alina Stefan ◽  
Mircea Cotlet ◽  
Johan Hofkens ◽  
Jianqiag Qu ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Single Molecule ◽  
Intramolecular Electron Transfer ◽  
Single Molecule Level

scholarly journals Transition from stochastic events to deterministic ensemble average in electron transfer reactions revealed by single-molecule conductance measurement

2019 ◽  
Vol 116 (9) ◽  
pp. 3407-3412 ◽  
Author(s):  
Yueqi Li ◽  
Hui Wang ◽  
Zixiao Wang ◽  
Yanjun Qiao ◽  
Jens Ulstrup ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Single Molecule ◽  
Electron Transfer Reaction ◽  
Transfer Reactions ◽  
Ensemble Averaging ◽  
Electron Transfer Reactions ◽  
Single Molecule Level ◽  
Individual Reaction ◽  
Stochastic Events ◽  
The Individual

Electron transfer reactions can now be followed at the single-molecule level, but the connection between the microscopic and macroscopic data remains to be understood. By monitoring the conductance of a single molecule, we show that the individual electron transfer reaction events are stochastic and manifested as large conductance fluctuations. The fluctuation probability follows first-order kinetics with potential dependent rate constants described by the Butler–Volmer relation. Ensemble averaging of many individual reaction events leads to a deterministic dependence of the conductance on the external electrochemical potential that follows the Nernst equation. This study discloses a systematic transition from stochastic kinetics of individual reaction events to deterministic thermodynamics of ensemble averages and provides insights into electron transfer processes of small systems, consisting of a single molecule or a small number of molecules.

Electron transfer behaviour of biological macromolecules towards the single-molecule level

2003 ◽  
Vol 15 (18) ◽  
pp. S1873-S1890 ◽  
Author(s):  
Jingdong Zhang ◽  
Mikala Grubb ◽  
Allan G Hansen ◽  
Alexander M Kuznetsov ◽  
Anja Boisen ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Single Molecule ◽  
Biological Macromolecules ◽  
Single Molecule Level

Electron Transfer at the Single-Molecule Level in a Triphenylamine-Perylene Imide Molecule

ChemPhysChem ◽  
2005 ◽  
Vol 6 (5) ◽  
pp. 942-948 ◽  
Author(s):  
Toby D. M. Bell ◽  
Alina Stefan ◽  
Sadahiro Masuo ◽  
Tom Vosch ◽  
Marc Lor ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Single Molecule ◽  
Single Molecule Level
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