13C-13C distance measurements in U-13C, 15N-labeled peptides using rotational resonance width experiment with a homogeneously broadened matching condition

In this publication, we introduce a version of the rotational resonance width experiment with a homogeneously broadened matching condition. The increase in the bandwidth is achieved by the reduction of the proton decoupling power during mixing, which results in the reduction of zero-quantum relaxation, and broadens the rotational resonance condition. We show that one can achieve recoupling of the carbonyl-aliphatic side chain dipolar interactions band selectively, while avoiding the recoupling of strongly interacting C′-Cα and C′-Cβ spin pairs. The attenuation of the multi-spin effects in the presence of short zero-quantum relaxation enables a two-spin approximation to be employed for the analysis of the experimental data. The systematic error introduced by this approximation is estimated by comparing the results with a three-spin simulation. The experiment is demonstrated in [U-13C,15N]N-acetyl-l-Val-l-Leu dipeptide, where 11 distances, ranging from 2.5 to 6 Å, were measured.