Pulsed triple electron resonance (TRIER) for dipolar correlation spectroscopy

Two-Dimensional Distance Correlation Maps from Pulsed Triple Electron Resonance (TRIER) on Proteins with Three Paramagnetic Centers

“…The TRIER experiment correlates inter spin distances of molecules that contain three electron spins. A detailed discussion on the TRIER sequence itself and all pathways that can lead to a modulation of the echo can be found in [15].…”

“…1b). In our initial work on TRIER [15] we used linearly frequency-swept pulses (chirp pulses) [17] with smoothed edges for the detection sequence and asymmetric hyperbolic secant (HS) pulses [28,29] for pumping. Meanwhile we have also tested Gaussian [30,31] and Gaussian cascade (GC) [32][33][34] pulses and compared their excitation windows and the resulting sensitivity and modulation depth.…”

“…Even in cases where the isolated spin pair approximation is not violated, full structural information on the system may not be obtainable if multiple conformations are populated [14]. To tackle this problem we recently introduced the triple electron resonance (TRIER) experiment [15] for systems with more than two paramagnetic centers. TRIER requires the selective excitation of three distinct subsets of spins with sufficiently high probability.…”

“…Besides enhancing the excitation bandwidth, frequency-swept pulses can allow for more precise control of spin systems through adiabatic passage [22] even in the presence of a strongly varying resonator profile through the principle of offset-independent adiabaticity [17,23]. Thanks to the excitation of larger spin fractions, signal intensity can be increased [18,19] and this in turn makes it possible to conduct new correlation experiments [15,[24][25][26]. Two overview articles on state-of-the-art EPR with frequency-swept pulses have recently been published [16,27].…”

“…1a) correlating dipolar frequencies that stem from the same molecule. In our initial work on TRIER [15] we obtained correlation spectra for several model compounds. Here, we demonstrate that we are able to obtain two-dimensional distance correlation maps and apply TRIER to protein samples of current interest.…”