Analysis and elimination of artifacts in indirect covariance NMR spectra via unsymmetrical processing

  title={Analysis and elimination of artifacts in indirect covariance NMR spectra via unsymmetrical processing},
  author={Kirill A. Blinov and Nicolay I. Larin and M. Kvasha and Arvin Moser and Antony J. Williams and Gary E. Martin},
  journal={Magnetic Resonance in Chemistry},
Indirect covariance NMR offers an alternative method of extracting spin–spin connectivity information via the conversion of an indirect‐detection heteronuclear shift‐correlation data matrix to a homonuclear data matrix. Using an IDR (inverted direct response)‐HSQC‐TOCSY spectrum as a starting point for the indirect covariance processing, a spectrum that can be described as a carbon–carbon COSY experiment is obtained. These data are analogous to the autocorrelated 13C–13C double quantum… 

Unsymmetrical indirect covariance processing of hyphenated and long-range heteronuclear 2D NMR spect

Recent reports have demonstrated the unsymmetrical indirect covariance combination of discretely acquired 2D NMR experiments into spectra that provide an alternative means of accessing the

Application of unsymmetrical indirect covariance NMR methods to the computation of the 13C↔15N HSQC‐IMPEACH and 13C↔15N HMBC‐IMPEACH correlation spectra

Correlations for carbon resonances long‐range coupled to a protonated carbon in the 1H13C HMBC spectrum are transferred via the long-range 1H 15N coupling pathway in the1H15N IMPEACH spectrum to afford a much broader range of correlation possibilities in the 13C15N HMBC‐IMPEACH correlation spectrum.

Using indirect covariance spectra to identify artifact responses in unsymmetrical indirect covariance calculated spectra

Responses contained in indirect covariance processed HSQC spectra are reported as a means for the identification of artifacts in bothirect covariance and unsymmetrical indirect covariances processed 2D NMR spectra.

Using indirect covariance processing for structure elucidation of small molecules in cases of spectral crowding

The investigation suggests that moderate spectral congestion in either proton or carbon domain leads to a number of artifacts that does not hamper signal assignment but lowers the level of confidence on de novo structure elucidation.

13C-15N Connectivity networks via unsymmetrical indirect covariance processing of 1H-13C HSQC and 1H

Long-range 1H-15N heteronuclear shift correlation methods at natural abundance to facilitate the elucidation of small molecule structures have assumed a role of growing importance over the past

Multistep correlations via covariance processing of COSY/GCOSY spectra: opportunities and artifacts

Results obtained from covariance‐processed GCOSY spectra are fully analyzed and compared to normally processed COSY and 80 ms TOCSY spectra and the origin of artifact responses is analyzed.

(13)C-(15)N correlation via unsymmetrical indirect covariance NMR: application to vinblastine.

The elimination of artifact responses with aromatic solvent-induced shifts (ASIS) is shown in addition to a method of forecasting potential artifact responses through the indirect covariance processing of the GHSQC spectrum used in the unsymmetrical indirect covariances processing.

Long‐range carbon–carbon connectivity via unsymmetrical indirect covariance processing of HSQC and HMBC NMR data

Using experimentally discrete HSQC and HMBC data sets, it is shown that unsymmetrical indirect covariance processing of the pair of NMR spectra affords a presentation containing long‐range carbon–carbon connectivity information.

Z-matrix formalism for quantitative noise assessment of covariance nuclear magnetic resonance spectra.

This work presents analytical relationships as well as simulated and experimental results characterizing the propagation of noise by unsymmetric covariance NMR processing, which concatenates two NMR spectra along a common dimension, resulting in a new spectrum showing spin correlations as cross peaks that are not directly measured in either of the two input spectra.



Covariance nuclear magnetic resonance spectroscopy.

Covariance nuclear magnetic resonance (NMR) spectroscopy is introduced, which is a new scheme for establishing nuclear spin correlations from NMR experiments that neither involves a second Fourier transformation nor does it require separate phase correction or apodization along the indirect dimension.

Inverted and suppressed direct response HMQC-TOCSY spectra-A convenient method of spectral editing

HMQC-TOCSY spectra provide a convenient means of establishing proton-proton connectivities in congested spectra of complex aromatic heterocycles. Advantage is taken of the greater dispersion of the

Theory of covariance nuclear magnetic resonance spectroscopy.

It is shown that for a large class of 2D NMR experiments the covariance spectrum and the 2D Fourier transform spectrum can be related to each other by means of Parseval's theorem.

Autocorrelated 13C-13C double quantum coherence two-dimensional NMR spectroscopy: utilization of a modified version of the technique as an adjunct in the total assignment of the 1H- and 13C-NMR spectra of the mutagen phenanthro[3,4-b]thiophene

Development of successively higher field nmr spectrometers has facilitated the study of increasingly more complex molecules, although smaller molecules such as phenanthro[3,4-b]thiophene still offer

Disentangling coupling and NOE pathways involving poorly resolved proton signals: HMQC‐TOCSY and HMQC‐NOESY

COSY and NOESY frequently fail when key proton signals are poorly resolved because of the proximity of the correlating off‐diagonal responses to the diagonal. Proton‐coupled heteronuclear multiple

Structure Elucidation from 2D NMR Spectra Using the StrucEluc Expert System: Detection and Removal of Contradictions in the Data

Algorithm methods for the detection and removal of contradictions in 2D NMR data that have been developed in support of StrucEluc are described, based on the analysis of molecular connectivity diagrams, MCDs and tested by solving 50 structural problems containing contradictions.

A Comparison of the hyphenated experiments GHMQC‐TOCSY and GHSQC‐TOCSY

Heteronuclear shift correlations generally may be established using either the multiple quantum-based GHMQC experiment or, alternately, the single quantum-based GHSQC experiment. A scant few reports

Pure absorption phase gradient‐enhanced HMQC‐TOCSY with direct response editing

Pulsed field gradients (PFG) have the potential to revolutionize further potent, inverse‐detected structural NMR techniques by eliminating artifacts and thermal noise in data taken with very small