An arbitrary pulse shaping module at X-band (10 GHz) frequencies will be integrated into an EPR spectrometer that will lead to unprecedented and fundamentally important advances, including dramatic enhancement of excitation bandwidths, reduction of the prohibitively long dead times of current pulsed EPR instruments, and the experimental realization of Fourier Transform EPR with high spectral resolution. The implementation of arbitrarily shaped microwave pulses will also enable the next generation of quantitative and time-resolved Overhauser DNP spectroscopy to probe the dynamics of the otherwise invisible, loosely bound hydration water around proteins with site specificity. The proposed development will capitalize on state of the art integrated circuit components to generate X-band waveforms, whose amplitude and phase can be specified on the fly with sub-ns resolution. This control, coupled with the unsurpassed, built-in flexibility of a commercial pulsed EPR spectrometer will offer an instrument with a wide range of qualities and capabilities novel to pulsed EPR and DNP.
State of the art EPR spectrometers do not yet offer the ability to shape individual pulses, as has routinely been done in modern NMR and MRI experiments for 25 years. This work proposes, for the first time, to implement arbitrarily shaped pulses for EPR experiments at the most commonly used X-band frequencies. This development has the potential to dramatically advance the accuracy, time resolution, and spectral resolution of current pulsed EPR and DNP experiments, allowing them to measure structural parameters, interactions, and dynamics of complex and large biological systems that are inaccessible to other methods.
