Proton to Carbon-13 INEPT in Solid-State NMR Spectroscopy

Abstract

A refocused INEPT through-bond coherence transfer technique is demonstrated for NMR of rigid organic solids and is shown to provide a valuable building block for the development of NMR correlation experiments in biological solids. The use of efficient proton homonuclear dipolar decoupling in combination with a direct spectral optimization procedure provides minimization of the transverse dephasing of coherences and leads to very efficient through-bond (1)H-(13)C INEPT transfer for crystalline organic compounds. Application of this technique to 2D heteronuclear correlation spectroscopy leads to up to a factor of 3 increase in sensitivity for a carbon-13 enriched sample in comparison to standard through-bond experiments and provides excellent selectivity for one-bond transfer. The method is demonstrated on a microcrystalline sample of the protein Crh (2 x 10.4 kDa).

Gradients in Wall Mechanics and Polysaccharides along Growing Inflorescence Stems

“…13 C DP and 13 C CP spectra were measured under 10 kHz MAS at 293 K. A spin-lock contact time of 0.5 ms and a recycle delay of 2 s were used for CP spectra. Refocused INEPT (Elena et al, 2005) spectra were measured under 13.5 kHz MAS at 293 K to selectively detect highly dynamic segments such as pectin side chains. A recycle delay of 3.5 s and a total polarization transfer time of 6 ms, which consists of two delays of 1.8 ms followed by two delays of 1.2 ms, were used for the INEPT experiments.…”

Powder crystallography of pharmaceutical materials by combined crystal structure prediction and solid-state 1H NMR spectroscopy

“…The 2D refocused 1 H-13 C INEPT 46 NMR spectra were recorded with a 4 mm double resonance probe at 12.5 kHz MAS. The SPINAL-64 45 sequence at a proton  1 of 100 kHz was used for heteronuclear decoupling.…”

Unexpected effects of third-order cross-terms in heteronuclear spin systems under simultaneous radio-frequency irradiation and magic-angle spinning NMR

“…As noted in the original reference, small, but consistent, discrepancies were observed between apparent 1 LG-CP, 11 or refocused INEPT. 23 (c) Superposition of the same region from 13 C, 1 H HETCOR (500 MHz, 12.5 kHz MAS) spectra of terbutaline sulfate form B recorded using contact times of (red) 150 μs and (grey/black) 350 μs. The long-range cross peaks (black) involving the two C6 resonances have subtly different apparent 1 H shifts compared to short-range correlations involving the same hydrogens (red).…”

“…spin-echo evolution periods have also been presented and shown to be applicable for spectral editing and the determination of 1 J CH couplings for typical organic compounds, 22,23 including the use of measured J couplings to determine the conformation of surface-absorbed catalytic species. 24 This paper investigates two experimental phenomena associated with the application of homonuclear 1 H decoupling in heteronuclear 13 C, 1 H solid-state MAS NMR; firstly, changes in the apparent 1 H chemical shift of correlation peaks in 1 H, 13 C two-dimensional experiments depending on whether there is or is not a one-bond 13 C-1 H dipolar coupling, and secondly, the observation of a much faster dephasing in a 13 C{ 1 H} heteronuclear spin-echo experiment under homonuclear 1 H decoupling as compared to heteronuclear 1 H decoupling.…”