Proton assisted recoupling at high spinning frequencies.

We demonstrate the successful application of (13)C-(13)C proton assisted recoupling (PAR) on [U-(13)C,(15)N] N-f-MLF-OH and [U-(13)C,(15)N] protein GB1 at high magic angle spinning (MAS) frequencies (omega(r)/2pi = 65 kHz). Specifically, by combining PAR mixing with low power heteronuclear decoupling (omega(1H)/2pi approximately 16 kHz) and high spinning frequencies, we obtain high resolution 2D spectra displaying long-range (13)C-(13)C contacts from which distance estimates can be extracted. These experiments therefore demonstrate the possibility of performing high resolution structural studies in the limit of high spinning frequency and low power (1)H decoupling, a regime which optimizes the resolution of protein samples and preserves their integrity.