Abstract
Proton ((1)H) detection methodologies in solid-state NMR (SSNMR) have revolutionized the field allowing for probing of new frontiers in determining the structure and dynamics within biological systems and materials. While approaches that maximally leverage the high gyromagnetic ratio of (1)H detection have enhanced sensitivity and resolution of SSNMR experiments, the radiofrequency (rf) circuit of magic-angle spinning (MAS) probes is not well optimized for (1)H detection, limiting the overall signal-to-noise ratio (SNR). Rather, SSNMR probes have historically been optimized for lower gamma nuclei such as (13)C and below. Here we present a design with an inner coil for proton ((1)H) to maximize (1)H sensitivity. Optimizing the (1)H channel resulted in a 1.33-2-fold increase in SNR with (1)H detection in a one-dimensional experiment. An outer coil is tuned to the (13)C and (15)N frequencies, with excellent B(1) homogeneity on all three channels. Using this design, we find that the sensitivity scales better than the theoretical expectations from 600 MHz to 750 MHz, due to a combination of the improved rf efficiency and B(1) homogeneity. We also demonstrate these improvements on a model protein system (GB1) with a 4D experiment collected in less than a day.