1 research outputs found
Triarylmethyl Labels: Toward Improving the Accuracy of EPR Nanoscale Distance Measurements in DNAs
Triarylmethyl (trityl, TAM) based
spin labels represent a promising
alternative to nitroxides for EPR distance measurements in biomolecules.
Herewith, we report synthesis and comparative study of series of model
DNA duplexes, 5′-spin-labeled with TAMs and nitroxides. We
have found that the accuracy (width) of distance distributions obtained
by double electron–electron resonance (DEER/PELDOR) strongly
depends on the type of radical. Replacement of both nitroxides by
TAMs in the same spin-labeled duplex allows narrowing of the distance
distributions by a factor of 3. Replacement of one nitroxide by TAM
(orthogonal labeling) leads to a less pronounced narrowing but at
the same time gains sensitivity in DEER experiment due to efficient
pumping on the narrow EPR line of TAM. Distance distributions in nitroxide/nitroxide
pairs are influenced by the structure of the linker: the use of a
short amine-based linker improves the accuracy by a factor of 2. At
the same time, a negligible dependence on the linker length is found
for the distribution width in TAM/TAM pairs. Molecular dynamics calculations
indicate greater conformational disorder of nitroxide labels compared
to TAM ones, thus rationalizing the experimentally observed trends.
Thereby, we conclude that double spin-labeling using TAMs allows obtaining
narrower spin–spin distance distributions and potentially more
precise distances between labeling sites compared to traditional nitroxides