title: Spin diffusion driven by R-symmetry sequences: applications to homonuclear correlation spectroscopy in MAS NMR of biological and organic solids.
abstract: We present a family of homonuclear (13)C-(13)C magic angle spinning spin diffusion experiments, based on R2(n)(v) (n = 1 and 2, v = 1 and 2) symmetry sequences. These experiments are well suited for (13)C-(13)C 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 R2(1)(1), R2(2)(1), and R2(2)(2) sequences result in excellent quality correlation spectra both in model compounds and in proteins. Under these conditions, individual R2(n)(v) display different polarization transfer efficiency dependencies on isotropic chemical shift differences: R2(2)(1) recouples efficiently both small and large chemical shift differences (in proteins these correspond to aliphatic-to-aliphatic and carbonyl-to-aliphatic correlations, respectively), while R2(1)(1) and R2(2)(2) exhibit the maximum recoupling efficiency for the aliphatic-to-aliphatic or carbonyl-to-aliphatic correlations, respectively. At moderate MAS frequencies (10-20 kHz), all R2(n)(v) 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-(13)C,(15)N]-alanine and the [U-(13)C,(15)N] N-formyl-Met-Leu-Phe (MLF) tripeptide. Further applications of this approach are illustrated for several proteins: spherical assemblies of HIV-1 U-(13)C,(15)N CA protein, U-(13)C,(15)N-enriched dynein light chain DLC8, and sparsely (13)C/uniformly (15)N enriched CAP-Gly domain of dynactin. Due to the excellent performance and ease of implementation, the presented R2(n)(v) 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.
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States.
authors.forename: Guangjin
authors.initials: G
authors.lastname: Hou
authors.forename: Si
authors.initials: S
authors.lastname: Yan
authors.forename: Shangjin
authors.initials: S
authors.lastname: Sun
authors.forename: Yun
authors.initials: Y
authors.lastname: Han
authors.forename: In-Ja L
authors.initials: IJ
authors.lastname: Byeon
authors.forename: Jinwoo
authors.initials: J
authors.lastname: Ahn
authors.forename: Jason
authors.initials: J
authors.lastname: Concel
authors.forename: Ago
authors.initials: A
authors.lastname: Samoson
authors.forename: Angela M
authors.initials: AM
authors.lastname: Gronenborn
authors.forename: Tatyana
authors.initials: T
authors.lastname: Polenova
mesh_terms: D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009930:Organic Chemicals / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*
chemical_list: D009930:Organic Chemicals; D011506:Proteins