Photoblinking of Rhodamine 6G in Poly(vinyl alcohol):  Radical Dark State Formed through the Triplet

Zondervan, Rob; Kulzer, Florian; Orlinskiĭ, S. B.; Orrit, Michel

doi:10.1021/jp034723r

Cited by 251 publications

(353 citation statements)

References 44 publications

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“…Although we cannot formally rule out the possibility of a long-lived triplet state, our results suggest that the observed dark state is an additional state, subsequent to the triplet intermediate. Potential mechanisms for such a dark state include radical-ion formation and nuclear coordinate movement of the dye [23,24]. Previous studies have reported photoblinking of dye molecules with dark-state lifetimes ranging from milliseconds to tens of seconds [23], but none approaching the length of the Cy5 dark state described here.…”

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confidence: 60%

Short-Range Spectroscopic Ruler Based on a Single-Molecule Optical Switch

Blosser²,

2005

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We demonstrate a novel all-optical switch consisting of two molecules: a primary fluorophore that can be switched between its fluorescent and dark states by light of different wavelengths, and a secondary chromophore that facilitates switching. The interaction between the two molecules exhibits a distance dependence much steeper than that of Förster resonance energy transfer. This enables the switch to act as a ruler with the capability to probe distances difficult to access by other spectroscopic methods, thus presenting a new tool for the study of biomolecules at the singlemolecule level.Single-molecule technologies have made a significant impact in many areas of science and engineering, ranging from electronics and photonics to molecular and cell biology. The detection of single biomolecules has transformed the way we study biological systems [1][2][3][4][5][6][7]. It is now evident that proteins, RNA and even DNA molecules are much more dynamic than previously thought, exhibiting structural dynamics essential for their function. Experiments that probe the behaviour of individual molecules in real time have proven to be ideal for characterizing these structural dynamics and their functional implications. Förster resonance energy transfer (FRET) is the most widely adopted technique for studying the conformational dynamics of individual biomolecules [6][7][8][9]. The FRET efficiency ε between a donor and an acceptor fluorophore depends on the intermolecular distance R, with ε = 1 / (1 + (R / R 0 ) 6 ). The Förster radius R 0 is typically 4 -6 nm for donor-acceptor pairs that are sufficiently bright to be detected at the single-molecule level. Therefore, single-molecule FRET is a useful probe of conformational changes on the order of several nanometers [6][7][8][9][10][11][12]. Few methods exist for the study of structural dynamics at shorter length scales. A promising technique for monitoring angstrom-scale distances, based on electron transfer, has recently been demonstrated using a flavin enzyme [13]. However, the length scale of 1 -3 nm remains difficult to access by non-invasive single-molecule techniques.In this work, we demonstrate a single-molecule optical switch which can function as a shortrange spectroscopic ruler to probe distances down to 1 nm. The molecular switch is based on a cyanine dye, Cy5, which we designate as the primary switch molecule, and a secondary chromophore, Cy3, which facilitates switching of the Cy5. For the purpose of single-molecule †To whom correspondence should be addressed. E-mail: zhuang@chemistry.harvard.edu. * These authors contributed equally to this work detection, the Cy5 and Cy3 were attached to opposite strands of a double-stranded DNA molecule and immobilized on a fused quartz surface through a streptavidin-biotin linkage (Fig. 1A). Molecules immobilized on a polyethylene glycol (PEG)-coated surface yielded similar results. Individual Cy5/DNA/Cy3 constructs were imaged in Tris buffer (pH 7.5) with an oxygen scavenging system to reduce the photobleaching rate...

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confidence: 60%

Short-Range Spectroscopic Ruler Based on a Single-Molecule Optical Switch

Blosser²,

2005

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“…It has been noted by Zondervan et al that dark states other than the triplet, like the radical state, can drastically affect photobleaching [16], as now strongly and directly evidenced by the results above. Using single-molecule fluorescence measurements, we cannot distinguish whether electron tunneling takes place from the singlet excited state or from the triplet state [14]. Further experiments, e.g., exploiting the heavy-atom effect to increase population of the triplet state [3], are needed to resolve this issue.…”

Section: Prl 95 097401 (2005) P H Y S I C a L R E V I E W L E T T E mentioning

confidence: 97%

“…Such LD states have been extensively studied on semiconductor nanocrystals [9][10][11][12][13], yet only few studies on other types of single emitters have been reported [4,6,14]. In the case of fluorescent organic molecules, the LD states are discussed in terms of the reversible formation of nonfluorescent photo-oxidation products [7,15], and the formation of radical anions or cations via intersystem crossing [14] or electron tunneling processes [4]. So far, however, data on LD state dynamics in single molecules have been hard to acquire.…”

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confidence: 99%

Power-Law-Distributed Dark States are the Main Pathway for Photobleaching of Single Organic Molecules

et al. 2005

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We exploit the strong excitonic coupling in a superradiant trimer molecule to distinguish between longlived collective dark states and photobleaching events. The population and depopulation kinetics of the dark states in a single molecule follow power-law statistics over 5 orders of magnitude in time. This result is consistent with the formation of a radical unit via electron tunneling to a time-varying distribution of trapping sites in the surrounding polymer matrix. We furthermore demonstrate that this radicalization process forms the dominant pathway for molecular photobleaching.

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“…Curiously, almost every nanoscale fluorescent object is known to exhibit fluorescence blinking. For semiconductor quantum dots and solubilised chromophores, the dominant underlying molecular mechanism was shown to involve ionisation, in the former due to a photoassisted Auger process [27,28] and in the latter, longliving, dark radical states were populated via triplet states [29]. For LHC2, containing 54 chromophores, one might similarly expect radical states to be responsible for fluorescence blinking.…”

Section: Photoactive Control Over the Intrinsic Protein Disordermentioning

confidence: 99%

Design principles of natural light-harvesting as revealed by single molecule spectroscopy

Krüger

Grondelle

2016

Physica B: Condensed Matter

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Biology offers a boundless source of adaptation, innovation, and inspiration. A wide range of photosynthetic organisms exist that are capable of harvesting solar light in an exceptionally efficient way, using abundant and low-cost materials. These natural light-harvesting complexes consist of proteins that strongly bind a high density of chromophores to capture solar photons and rapidly transfer the excitation energy to the photochemical reaction centre. The amount of harvested light is also delicately tuned to the level of solar radiation to maintain a constant energy throughput at the reaction centre and avoid the accumulation of the products of charge separation. In this Review, recent developments in the understanding of light harvesting by plants will be discussed, based on results obtained from single molecule spectroscopy studies. Three design principles of the main light-harvesting antenna of plants will be highlighted: (a) fine, photoactive control over the intrinsic protein disorder to efficiently use intrinsically available thermal energy dissipation mechanisms; (b) the design of the protein microenvironment of a low-energy chromophore dimer to control the amount of shade absorption; (c) the design of the exciton manifold to ensure efficient funneling of the harvested light to the terminal emitter cluster.

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Photoblinking of Rhodamine 6G in Poly(vinyl alcohol): Radical Dark State Formed through the Triplet

Cited by 251 publications

References 44 publications

Short-Range Spectroscopic Ruler Based on a Single-Molecule Optical Switch

Short-Range Spectroscopic Ruler Based on a Single-Molecule Optical Switch

Power-Law-Distributed Dark States are the Main Pathway for Photobleaching of Single Organic Molecules

Design principles of natural light-harvesting as revealed by single molecule spectroscopy

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