Two-photon time-resolved anisotropy, FCS, and photon antibunching reveal excitonic coupling between fluorescent proteins (Conference Presentation)

2020 ◽  
Author(s):  
Steven S. Vogel
Keyword(s):  
Fluorescent Proteins ◽  
Time Resolved ◽  
Two Photon ◽  
Photon Antibunching ◽  
Excitonic Coupling

scholarly journals Real-time observation of tetrapyrrole binding to an engineered bacterial phytochrome

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Yusaku Hontani ◽  
Mikhail Baloban ◽  
Francisco Velazquez Escobar ◽  
Swetta A. Jansen ◽  
Daria M. Shcherbakova ◽  
...  
Keyword(s):  
Real Time ◽  
Rational Design ◽  
Near Infrared ◽  
Fluorescent Proteins ◽  
Covalent Bond ◽  
Binding Pocket ◽  
Tissue Imaging ◽  
Covalent Attachment ◽  
Time Resolved

AbstractNear-infrared fluorescent proteins (NIR FPs) engineered from bacterial phytochromes are widely used for structural and functional deep-tissue imaging in vivo. To fluoresce, NIR FPs covalently bind a chromophore, such as biliverdin IXa tetrapyrrole. The efficiency of biliverdin binding directly affects the fluorescence properties, rendering understanding of its molecular mechanism of major importance. miRFP proteins constitute a family of bright monomeric NIR FPs that comprise a Per-ARNT-Sim (PAS) and cGMP-specific phosphodiesterases - Adenylyl cyclases - FhlA (GAF) domain. Here, we structurally analyze biliverdin binding to miRFPs in real time using time-resolved stimulated Raman spectroscopy and quantum mechanics/molecular mechanics (QM/MM) calculations. Biliverdin undergoes isomerization, localization to its binding pocket, and pyrrolenine nitrogen protonation in <1 min, followed by hydrogen bond rearrangement in ~2 min. The covalent attachment to a cysteine in the GAF domain was detected in 4.3 min and 19 min in miRFP670 and its C20A mutant, respectively. In miRFP670, a second C–S covalent bond formation to a cysteine in the PAS domain occurred in 14 min, providing a rigid tetrapyrrole structure with high brightness. Our findings provide insights for the rational design of NIR FPs and a novel method to assess cofactor binding to light-sensitive proteins.

scholarly journals Picosecond time-resolved photon antibunching measures nanoscale exciton motion and the true number of chromophores

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gordon J. Hedley ◽  
Tim Schröder ◽  
Florian Steiner ◽  
Theresa Eder ◽  
Felix J. Hofmann ◽  
...  
Keyword(s):  
Rational Design ◽  
Three Dimensional ◽  
Dna Origami ◽  
Fluorescent Nanoparticles ◽  
Time Resolved ◽  
Exciton Diffusion ◽  
Polymer Aggregates ◽  
True Number ◽  
Particle Level ◽  
Photon Antibunching

AbstractThe particle-like nature of light becomes evident in the photon statistics of fluorescence from single quantum systems as photon antibunching. In multichromophoric systems, exciton diffusion and subsequent annihilation occurs. These processes also yield photon antibunching but cannot be interpreted reliably. Here we develop picosecond time-resolved antibunching to identify and decode such processes. We use this method to measure the true number of chromophores on well-defined multichromophoric DNA-origami structures, and precisely determine the distance-dependent rates of annihilation between excitons. Further, this allows us to measure exciton diffusion in mesoscopic H- and J-type conjugated-polymer aggregates. We distinguish between one-dimensional intra-chain and three-dimensional inter-chain exciton diffusion at different times after excitation and determine the disorder-dependent diffusion lengths. Our method provides a powerful lens through which excitons can be studied at the single-particle level, enabling the rational design of improved excitonic probes such as ultra-bright fluorescent nanoparticles and materials for optoelectronic devices.

Time-resolved two-photon photoemission at metal-dielectric interfaces

2005 ◽  
Vol 45 (1-2) ◽  
pp. 181-194 ◽  
Author(s):  
Wolfram Berthold ◽  
Ulrich Höfer
Keyword(s):  
Time Resolved ◽  
Two Photon ◽  
Dielectric Interfaces

Two-photon time-resolved optogalvanic signals of neon

2009 ◽  
Vol 282 (23) ◽  
pp. 4552-4555 ◽  
Author(s):  
R. Omidyan ◽  
H. Farrokhpour ◽  
M. Tabrizchi
Keyword(s):  
Time Resolved ◽  
Two Photon
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