[NMR paper] Broadband Homonuclear Correlation Spectroscopy Driven by Combined R2nv Sequences under Fast Magic Angle Spinning for NMR Structural Analysis of Organic and Biological Solids

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Broadband Homonuclear Correlation Spectroscopy Driven by Combined R2nv Sequences under Fast Magic Angle Spinning for NMR Structural Analysis of Organic and Biological Solids

Publication date: Available online 28 April 2013
Source:Journal of Magnetic Resonance

Author(s): Guangjin Hou , Si Yan , Julien Trebosc , Jean-Paul Amoureux , Tatyana Polenova

We recently described a family of experiments for R2 n v Driven Spin Diffusion (RDSD) spectroscopy suitable for homonuclear correlation experiments under fast MAS conditions (J. Am. Chem. Soc., 133, 2011, 3943). In these RDSD experiments, since the broadened second-order rotational resonance conditions are dominated by the radio frequency field strength and the phase shifts, as well as the size of reintroduced dipolar couplings, the different R2 n v sequences display unique polarization transfer behaviors and different recoupling frequency bandwidths. Herein, we present a series of modified R2 n v sequences, dubbed COmbined R2 n v -Driven (CORD), that yield broadband homonuclear dipolar recoupling and give rise to uniform distribution of cross peak intensities across the entire correlation spectrum. We report NMR experiments and numerical simulations demonstrating that these CORD spin diffusion sequences are suitable for broadband recoupling at a wide range of magnetic fields and MAS frequencies, including fast-MAS conditions (?r = 40 kHz and above). Since these CORD sequences are largely insensitive to dipolar truncation, they are well suited for the determination of long-range distance constraints, which are indispensable for the structural characterization of a broad range of systems. Using U-13C-alanine and U-13C,15N-histidine, we show that under fast-MAS conditions, the CORD sequences display polarization transfer efficiencies within broadband frequency regions that are generally higher than those offered by other existing spin diffusion pulse schemes. A 89-residue U-13C,15N-dynein light chain (LC8) protein has also been used to demonstrate that the CORD sequences exhibit uniformly high cross peak intensities across the entire chemical shift range.
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