Takeuchi K, Gal M, Takahashi H, Shimada I, Wagner G. HNCA-TOCSY-CANH experiments with alternate (13)C- (12)C labeling: a set of 3D experiment with unique supra-sequential information for mainchain resonance assignment.
J Biomol NMR 2011;
49:17-26. [PMID:
21110064 PMCID:
PMC3072286 DOI:
10.1007/s10858-010-9456-2]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 11/02/2010] [Indexed: 05/30/2023]
Abstract
Described here is a set of three-dimensional (3D) NMR experiments that rely on CACA-TOCSY magnetization transfer via the weak ³J(CαCα) coupling. These pulse sequences, which resemble recently described (13)C detected CACA-TOCSY (Takeuchi et al. 2010) experiments, are recorded in (1)H(2)O, and use (1)H excitation and detection. These experiments require alternate (13)C-(12)C labeling together with perdeuteration, which allows utilizing the small ³J(CαCα) scalar coupling that is otherwise masked by the stronger (1)J(CC) couplings in uniformly (13)C labeled samples. These new experiments provide a unique assignment ladder-mark that yields bidirectional supra-sequential information and can readily straddle proline residues. Unlike the conventional HNCA experiment, which contains only sequential information to the ¹³C(α) of the preceding residue, the 3D hnCA-TOCSY-caNH experiment can yield sequential correlations to alpha carbons in positions i-1, i + 1 and i-2. Furthermore, the 3D hNca-TOCSY-caNH and Hnca-TOCSY-caNH experiments, which share the same magnetization pathway but use a different chemical shift encoding, directly couple the (15)N-(1)H spin pair of residue i to adjacent amide protons and nitrogens at positions i-2, i-1, i + 1 and i + 2, respectively. These new experimental features make protein backbone assignments more robust by reducing the degeneracy problem associated with the conventional 3D NMR experiments.
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