Pulsed EPR dipolar spectroscopy at Q- and G-band on a trityl biradical

• DOI: 10.1039/c5cp03671b
• Publication Date: 2015-08-26T08:00:25Z
• Authors: D. Akhmetzyanov; P. Schöps; A. Marko; N. C. Kunjir; S. Th. Sigurdsson; T. F. Prisner
• Keywords: Site-directed spin labeling; Pulsed EPR

Pulsed electron paramagnetic resonance (EPR) spectroscopy is a valuable technique for the precise determination of distances between spin labels that are covalently attached to macromolecules. Nitroxides have commonly been utilised as tags biomolecules, but trityl radicals recently developed alternative labels. Trityls exhibit longer relaxation times and higher stability than nitroxides under in vivo conditions. So far, only used pulsed EPR dipolar (PDS) at X-band (9.5 GHz), Ku-band (17.2 GHz) Q-band (34 frequencies. In this study we investigated biradical by PDS G-band (180 Due small spectral width (30 MHz) frequencies, single frequency techniques, like double-quantum coherence (DQC) refocusing couplings (SIFTER), work very efficiently. Hence, DQC SIFTER experiments were performed results compared; yielding signal noise ratio four DQC. At frequencies resolved axially symmetric g-tensor anisotropy exhibited 130 MHz. Thus, double (PELDOR/DEER) obtained different pump-probe positions across spectrum was reveal distances. Such multi-frequency approach should also be applicable determine structural information on biological macromolecules tagged with