Sensitivity optimization in pulse EPR experiments with photo-labels by multiple-echo-integrated dynamical decoupling

Abstract

Photo-excited triplet states represent a new type of spin labels in pulse electron paramagnetic resonance (EPR), attracting an increasing attention because of their unique spectroscopic properties. Despite certain advantages, the...

Revealing light-induced structural shifts in G-quadruplex-porphyrin complexes: a pulsed dipolar EPR study

“…48–51 In this approach, called light-induced pulsed dipolar spectroscopy (LiPDS), the measurement of dipole–dipole interactions occurs between the excited triplet state and another paramagnetic center, usually nitroxide. The photolabels offer the ability to detect a highly intense polarized signal 50–54 or employ a laser pulse instead of a microwave pumping pulse. 49,52,55–60 Except for spectroscopic advantages, LiPDS makes it possible to look at the structure of biological complexes that contain photosensitizers in novel ways.…”

Direct Comparison between Förster Resonance Energy Transfer and Light-Induced Triplet–Triplet Electron Resonance Spectroscopy

“…Light-induced PDS methods have been developed based on the photogenerated triplet state of a 5­(4′-carboxyphenyl)- 10,15,20- triphenylporphyrin (TPP) moiety as photoswitchable spin-label, − allowing measurement of its dipolar interaction with permanent paramagnetic centers, e.g., nitroxide, in synthetic model peptides ,,− and heme-containing proteins. ,− The triplet can be used for detection and the permanent paramagnetic center pumped, as in light induced DEER, or the triplet state generated during the pulse sequence and the permanent paramagnetic center detected, as in laser-induced magnetic dipole spectroscopy . Subsequent studies replaced TPP with other chromophores. − The photogenerated triplet is advantageous over permanent paramagnetic centers due to its strong spin polarization . Distances up to ca.…”