Fullerene-based triplet spin labels: methodology aspects for pulsed dipolar EPR spectroscopy

Abstract

Triplet states of photoexcited organic molecules are promising spin labels with advanced spectroscopic properties for Pulsed Dipolar Electron Paramagnetic Resonance (PD EPR) spectroscopy. Recently proposed triplet fullerene labels have shown...

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

“…Moreover, the observed echo can undergo damping by a laser flash because of the ‘quenching’ of part of the TAM signal in compactly folded C 60 TAM dyads. 14 Since the modulation depth in ReLaserIMD is relatively small (∼30%), as an approximation we assumed that the fluctuation of the laser intensity causes a wobbling of the overall echo signal ( I echo ).…”

“…Photo-excited triplet labels attract increasing attention due to their unique spectroscopic properties. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] The key feature of the photo-excited triplet states is a nonequilibrium electron spin polarization formed upon singlet-triplet intersystem crossing (ISC). 17,18 If this electron spin polarization is strong (called hyperpolarization), the intensity of the EPR signal of the triplet state may significantly exceed that of stable radicals, thus allowing highly sensitive experiments on photo-labels.…”

Erythrosin B as a New Photoswitchable Spin Label for Light-Induced Pulsed EPR Dipolar Spectroscopy

“…The photogenerated triplet state of organic chromophores has recently been introduced as a photoswitchable spin label, sparking a paradigm shift in PDS and starting the field of light-induced PDS (LiPDS) [ 18 , 19 , 20 , 21 , 22 , 23 ]. The formation of the EPR-active triplet states of these chromophores following photoexcitation by pulsed laser irradiation allows the study of biomacromolecules without relying exclusively on permanent paramagnetic moieties.…”

Increasing the Modulation Depth of GdIII-Based Pulsed Dipolar EPR Spectroscopy (PDS) with Porphyrin–GdIII Laser-Induced Magnetic Dipole Spectroscopy

“…In initial studies of light-induced PDS, porphyrins were paired with nitroxide labels. , Other label combinations that have been reported since are fullerenes with trityl radicals or nitroxides , the combination of the fluorescent dyes Rose Bengal, Eosin Y, or Atto Thio12 with a nitroxide and two porphyrins, both of which are photoexcited . We opted for porphyrin as the transient spin label, because of its photostability and selected the porphyrin TNPP (Figure ) because of its water solubility .…”

“…Therefore, in a given measurement time, Gd III –Gd III DEER benefits from much more scans being accumulated than for TNPP-Gd III LaserIMD, which explains the better SNR of the former. As most transient labels used so far for LaserIMD require an SRT in the millisecond range, ,,,, the continuation of the development of transient spin labels with faster triplet relaxation times is necessary to open up the full possibilities of LaserIMD with Gd III -based spin labels.…”