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Light-Induced Triplet-Triplet Electron Resonance Spectroscopy
Arnau Bertran1, Kevin B Henbest1, Marta De Zotti2
1Centre for Advanced Electron Spin Resonance and Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.
The Journal of Physical Chemistry Letters
|December 11, 2020
Summary
We developed light-induced triplet-triplet electron resonance spectroscopy (LITTER) to measure distances between photoexcited molecules. This new method aids in determining molecular conformations without permanent paramagnetic labels.
Area of Science:
- Chemical Physics
- Spectroscopy
- Biophysics
Background:
- Electron spin resonance (ESR) pulse dipolar spectroscopy (PDS) is crucial for molecular structure determination.
- Current PDS techniques require a permanent paramagnetic center, limiting applications in biological systems.
- Photoexcited triplet states offer potential for probing molecular structures without permanent labels.
Purpose of the Study:
- Introduce a novel technique, light-induced triplet-triplet electron resonance spectroscopy (LITTER).
- Enable distance and angular distribution measurements between two photoexcited triplet states.
- Facilitate structural analysis of unmodified macromolecular systems and in-cell applications.
Main Methods:
- LITTER measures dipolar interactions between photoexcited triplet states.
- Demonstrated on a model bis-porphyrin peptide system.
- Combined with simulations and density functional theory (DFT) calculations.
Main Results:
- Determined distance and angular distributions of porphyrin moieties on a nanometer scale.
- Extracted precise distance distributions and relative orientations.
- Identified the dominant conformation of the bis-porphyrin peptide in frozen solution.
Conclusions:
- LITTER overcomes limitations of existing PDS methods by not requiring permanent paramagnetic moieties.
- The technique is suitable for in-cell applications and studying unmodified macromolecules.
- LITTER shows potential for integration with Förster resonance energy transfer (FRET) and cellular microscopy.
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