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Polarized two-photon photoselection in EGFP: Theory and experiment
T A Masters1, R J Marsh1, T S Blacker1
1Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom.
The Journal of Chemical Physics
|April 9, 2018
Summary
This study details two-photon photoselection, revealing hidden hexadecapolar alignment in fluorescent proteins. Findings clarify transition tensor structure and its relation to light absorption.
Area of Science:
- Photophysics
- Spectroscopy
- Biophysics
Background:
- Two-photon absorption (TPA) allows deeper tissue imaging and 3D resolution.
- Understanding excited state dynamics is crucial for advanced optical techniques.
- Fluorescent proteins are vital tools in biological research.
Purpose of the Study:
- To provide a theoretical framework for excited state ordering via two-photon photoselection.
- To investigate both quadrupolar and hexadecapolar transition dipole alignment.
- To determine the transition tensor structure in enhanced green fluorescent protein.
Main Methods:
- Theoretical modeling of two-photon photoselection.
- Linear and circular polarized two-photon absorption spectroscopy.
- Time-resolved single- and two-photon fluorescence anisotropy measurements.
Main Results:
- A complete theoretical description of excited state order was developed.
- The study quantified quadrupolar (K=2) and hexadecapolar (K=4) alignment.
- For enhanced green fluorescent protein, TPA is described by a planar transition tensor collinear with the S0 → S1 transition moment.
Conclusions:
- The findings elucidate the role of transition tensor symmetry in TPA.
- Near-infrared TPA in fluorescent proteins is assigned to a vibronically enhanced S0 → S1 transition.
- This work advances the understanding of photophysical processes in fluorescent molecules.
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