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. 2010 Feb 14;46(6):952-4.
doi: 10.1039/b920844e. Epub 2009 Dec 9.

Improving the Quality of 2D Solid-State NMR Spectra of Microcrystalline Proteins by Covariance Analysis

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Free PMC article

Improving the Quality of 2D Solid-State NMR Spectra of Microcrystalline Proteins by Covariance Analysis

Markus Weingarth et al. Chem Commun (Camb). .
Free PMC article

Abstract

Gaining time, resolution and sensitivity at the same time: covariance processing of two-dimensional NMR spectra of microcrystalline proteins improves spectral quality over conventional Fourier transformation despite a significant reduction of the experimental time.

Figures

Fig. 1
Fig. 1
Two-dimensional correlation spectra of microcrystalline Crh obtained with PARIS recoupling to induce a broad-band 13C-13C transfer of magnetization, processed by (a) covariance with N1 = 512, (b) 2D FT with N1 = 512, (c) covariance with N1 = 256 and (d) 2D FT with N1 = 256. The lowest contour levels lie five times above the noise level. PISSARRO decoupling with a proton rf field ν1H = 100 kHz was applied during both evolution and acquisition times.
Fig. 2
Fig. 2
Enlargement of the region of Fig. 1 containing cross-peaks between carbonyl and aliphatic carbons processed by (a) covariance with N1 = 512, (b) 2D FT with N1 = 512, (c) covariance with N1 = 256, and (d) 2D FT with N1 = 256. Green asterisks indicate weak but significant cross-peaks that can only be resolved in covariance spectra.
Fig. 3
Fig. 3
Increase of signal-to-noise ratio obtained with covariance processing (N1 = 512, panels a, d) in comparison with 2D FT processing (N1 = 512, panels b, e). Weak but unambiguous correlations appear in the covariance spectra that are hidden in the noise of 2D FT spectra.
Fig. 4
Fig. 4
Expansions of Fig. 1, showing the same spectral region above (a, c) and below (b, d) the main diagonal: (a), (b) covariance spectrum with N1 = 512 and (c), (d) the corresponding spectrum processed with 2D FT. The green asterisks indicate unassigned cross-peaks. The lowest contour levels are drawn at four times the noise level.

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