American Chemical Society
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Spin Diffusion Driven by R-Symmetry Sequences: Applications to Homonuclear Correlation Spectroscopy in MAS NMR of Biological and Organic Solids

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journal contribution
posted on 2011-03-23, 00:00 authored by Guangjin Hou, Si Yan, Shangjin Sun, Yun Han, In-Ja L. Byeon, Jinwoo Ahn, Jason Concel, Ago Samoson, Angela M. Gronenborn, Tatyana Polenova
We present a family of homonuclear 13C−13Cmagic angle spinning spin diffusion experiments, based on R2nv (n = 1 and 2, v = 1 and 2) symmetry sequences. These experiments are well suited for 13C−13C correlation spectroscopy in biological and organic systems and are especially advantageous at very fast MAS conditions, where conventional PDSD and DARR experiments fail. At very fast MAS frequencies the R211, R221, and R222 sequences result in excellent quality correlation spectra both in model compounds and in proteins. Under these conditions, individual R2nv display different polarization transfer efficiency dependencies on isotropic chemical shift differences: R221 recouples efficiently both small and large chemical shift differences (in proteins these correspond to aliphatic-to-aliphatic and carbonyl-to-aliphatic correlations, respectively), while R211 and R222 exhibit the maximum recoupling efficiency for the aliphatic-to-aliphatic or carbonyl-to-aliphatic correlations, respectively. At moderate MAS frequencies (10−20 kHz), all R2nv sequences introduced in this work display similar transfer efficiencies, and their performance is very similar to that of PDSD and DARR. Polarization transfer dynamics and chemical shift dependencies of these R2-driven spin diffusion (RDSD) schemes are experimentally evaluated and investigated by numerical simulations for [U−13C,15N]-alanine and the [U−13C,15N] N-formyl-Met-Leu-Phe (MLF) tripeptide. Further applications of this approach are illustrated for several proteins: spherical assemblies of HIV-1 U−13C,15N CA protein, U−13C,15N-enriched dynein light chain DLC8, and sparsely 13C/uniformly 15N enriched CAP-Gly domain of dynactin. Due to the excellent performance and ease of implementation, the presented R2nv symmetry sequences are expected to be of wide applicability in studies of proteins and protein assemblies as well as other organic solids by MAS NMR spectroscopy.