Single occupancy spectroelectrochemistry of freely diffusing flavin mononucleotide in zero-dimensional nanophotonic structures
| Autor: | Paul W. Bohn, Lawrence P. Zaino, Dane A. Grismer, Donghoon Han, Garrison M. Crouch |
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| Rok vydání: | 2015 |
| Předmět: |
Photons
education.field_of_study Flavin Mononucleotide Population Flavin mononucleotide Electrochemical Techniques Flavin group Chromophore Photochemistry Fluorescence Nanostructures Diffusion chemistry.chemical_compound Electron transfer chemistry Chemical physics Luminescent Measurements Light emission Gold Physical and Theoretical Chemistry Cyclic voltammetry education |
| Zdroj: | Faraday Discussions. 184:101-115 |
| ISSN: | 1364-5498 1359-6640 |
| DOI: | 10.1039/c5fd00072f |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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