Pulse induced resonance with angular dependent total enhancement of multi-dimensional solid-state NMR correlation spectra

We demonstrate a new resonance condition that obeys the relation ${\Delta}{\delta}=n{\nu}_{R}/2$, where ${\Delta}{\delta}$ is the chemical shift difference between two homonuclear-coupled spins, ${\nu}_{R}$ is the magic-angle spinning speed and $n$ is an integer. This modulation on the rotational resonance recoupling condition is obtained by the application of rotor-synchronous $^{1}$H pulses when at least one proton is dipolar-coupled to one of the homonuclear-coupled spins. We suggest a new experimental scheme entitled "pulse induced resonance with angular dependent total enhancement" (PIRATE) that can enhance proton-driven spin diffusion by the application of a single $^{1}$H pulse every rotor period. Experimental evidence is demonstrated on the two carbon spins of glycine and on the Y21M mutant of fd bacteriophage virus. Numerical simulations reveal the existence of the resonances and report on the important interactions governing this phenomena.