Available methods for molecular structure determination, based primarily on x-ray crystallography and Nuclear Magnetic Resonance (NMR) solution methods, have had limited success on the insoluble proteins that are critical to biological function. Various recent developments have enhanced the effectiveness of solids NMR methods incorporating Magic Angle sample Spinning (MAS), and considerable additional progress in such techniques continues. However, using stationary (non-MAS) high-power methods, such as PISEMA, have been very fruitful thus far in yielding structures of large, complex, helical membrane proteins. Preliminary work recently published by several leading research groups has demonstrated the value of advanced 3D methods that require solids NMR probes with major increases in RF field strengths required for significantly improved spectral resolution.
Doty Scientific has developed a high-power, non-spinning, triple-resonance probe at 900 MHz 1H with order-of-magnitude reduction in RF sample heating and substantial improvement in each of the remaining three most important and technically demanding specifications: RF field strength, spectral resolution, and S/N. Measurements performed in the 900 MHz magnet at the NHMFL in Tallahassee included CP experiments for 1H/13C with 4.6 μs π/2 pulse widths at 111 W on 1H and 180 W on 13C, and CP experiments for 1H/15N with 4.3 μs π/2 pulse widths at 920 W on 15N. Further details and multi-dimensional NMR experimental data will be shown. The probe also included a gradient coil which was tested to 157 G/cm in the magnet and demonstrated excellent linearity, efficiency, and recovery time.