Carbon-13 chemical shift anisotropy

Veeman, W. S.

doi:10.1016/0079-6565(84)80006-0

Cited by 275 publications

(131 citation statements)

References 60 publications

Supporting

Mentioning

122

Contrasting

Unclassified

Order By: Relevance

“…As indicated, the orientation of the carbon CS tensor PAS within the carbonyl fragment is well established (4,5). In agreement with the experimental results obtained here, the most shielded direction is invariably found to lie normal to the plane comprising the carbonyl group.…”

Section: (B) Carbon Chemical Shielding Tensor Calculationssupporting

confidence: 79%

“…The most shielded direction was associated with the normal to the aforementioned plane. Qualitatively, such an orientation is invariably observed for the carbonyl fragment (4,5). Consequently, based on the observed differences in the magnitudes of the three principal components of the carbon CS tensors in benzophenone and thiobenzophenone as well as simple electronic structure arguments, it was proposed that the two inplane principal components exchange orientation in thiobenzophenone with respect to benzophenone.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A solid-state ¹³C NMR and theoretical investigation of carbonyl and thiocarbonyl carbon chemical shift tensors

Kirby¹,

Lumsden²,

Wasylishen³

1995

Can. J. Chem.

View full text Add to dashboard Cite

The carbon chemical shift tensors of the carbonyl and thiocarbonyl groups of acetamide, thioacetamide, thioacetanilide, 4'-methoxyacetanilide, and 4'-methoxythioacetanilide have been experimentally determined using dipolar -chemical shift solid-state 13c NMR spectroscopy. The magnitudes of the three principal components of the carbon chemical shift tensors are found to exhibit marked variations between the carbonyl and thiocarbonyl functionalities. However, in contrast to the conclusions of an earlier comparative investigation involving benzophenone and thiobenzophenone, the orientations of the principal axis systems of these chemical shift tensors are found to be similar. These experimental results represent the first complete characterizations of the carbon chemical shift tensor in organic thiocarbonyls. The results of our ab initio GIAO and LORG calculations of carbon chemical shielding tensors in formaldehyde, thiofomaldehyde, formamide, and thioformamide as well as in acetamide and thioacetamide are in qualitative agreement with experiment. The findings of the present investigation provide conclusive evidence that the well-known isotropic deshielding of the carbon nucleus in the C=S group relative to C=O is primarily attributable to the decreased energy associated with the o tt T* excitation within the thiocarbonyl fragment. This result is in contrast with the conventional interpretation that the deshielding originates from a red shift in the C=S HOMO-LUMO n + T* transition.Key words: chemical shift tensors, solid-state I3C NMR, carbonyls, thiocarbonyls, ab initio calculations.RksumC : Utilisant les deplacements chimiques dipolaires de la spectroscopie RMN du I3c 2i I'ttat solide, on a determine exptrimentalement les tenseurs des dtplacements chimiques du carbone des groupes carbonyle et thiocarbonyle des acttamide, thioacetamide, thioacttanilide, 4'-mCthoxyacCtanilide et 4'-mCthoxythioacttanilide. On a trouvt que les amplitudes des trois principales composantes des tenseurs des dtplacements chimiques du carbone presentent des variations importantes entre les fonctions carbonyles et thiocarbonyles. Toutefois, en opposition avec les conclusions tirkes 2i partir d'une ttude comparative anttrieure impliquant la benzophenone et la thiobenzophtnone, on a trouvt que les orientations des principaux axes de rtftrence de ces tenseurs des dCsplacements chimiques sont semblables. Ces resultats exptrimentaux representent les premihres caractkrisations complktes du tenseur du dtplacement chimique des thiocarbonyles organiques. Les rtsultats de nos calculs ab initio GIAO et LORG des tenseurs d'tcran chimique du carbone dans les formaldthyde, thiofomaldChyde, formamide, thiofomamide ainsi qu'acttamide et thioacttamide sont en accord qualitatif avec les rtsultats expCrimentaux. Les observations faites dans le present travail fournissent des bases concluantes qui permettent d'attribuer le deblindage bien connu du noyau du carbone dans le groupe C=S par rapport au C=O 2i une diminution de l'energie associee B une e...

show abstract

Section: (B) Carbon Chemical Shielding Tensor Calculationssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

A solid-state ¹³C NMR and theoretical investigation of carbonyl and thiocarbonyl carbon chemical shift tensors

Kirby¹,

Lumsden²,

Wasylishen³

1995

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…Before discussing the results, some remarks should be larad¢ on the effect of protonation regarding the b~C .~MR signal of a carboxyl group [27]. Regarding the ¢I:hemical shift tensor of an aspartate as compared to a porotonated carboxyl group, the most sensitive element isso~,, which experiences an upfield shift in the order of .o_0 ppm upon protonation.…”

Section: Results and Discussionmentioning

confidence: 99%

Asp⁸⁵ is the only internal aspartic acid that gets protonated in the M intermediate and the purple‐to‐blue transition of bacteriorhodopsin A solid‐state¹³C CP‐MAS NMR investigation

1992

View full text Add to dashboard Cite

“…Sixteen transients were added for each t 1 increment (dw = nτ r ), and a total of 32 t 1 increments were used to record the spectra for NAV, Ala, and His. For 2D RNCSA experiments on U- 13 C, 15 N-Tyr-CTD CA protein, 4096 and 3072 transients were accumulated for each t 1 increment in the R8 1 3 -based 15 N σ 1 -CSA and R12 1 4 -based 13 C σ 2 -CSA measurements, respectively, and the same transients were used in the corresponding 2D recoupling of chemical shift anisotropy (ROCSA) experiments. The pulse delay was 2 s.…”

Section: A Materialsmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Even though select non-isotropic properties of chemical shift tensors can be obtained through solution-state NMR approaches, solid-state NMR spectroscopy is far more suitable for deriving the anisotropic information. 14 In solids, CSA can be directly measured by recording powder patterns in static powder samples, but these experiments suffer from poor sensitivity, spectral overlap when multiple chemical sites are present, and from broadening and distortion to the CSA line shapes introduced by a) Author to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Recoupling of chemical shift anisotropy by R-symmetry sequences in magic angle spinning NMR spectroscopy

Hou

Byeon

Ahn

et al. 2012

The Journal of Chemical Physics

View full text Add to dashboard Cite

C and15 N chemical shift (CS) interaction is a sensitive probe of structure and dynamics in a wide variety of biological and inorganic systems, and in the recent years several magic angle spinning NMR approaches have emerged for residue-specific measurements of chemical shift anisotropy (CSA) tensors in uniformly and sparsely enriched proteins. All of the currently existing methods are applicable to slow and moderate magic angle spinning (MAS) regime, i.e., MAS frequencies below 20 kHz. With the advent of fast and ultrafast MAS probes capable of spinning frequencies of 40-100 kHz, and with the superior resolution and sensitivity attained at such high frequencies, development of CSA recoupling techniques working under such conditions is necessary. In this work, we present a family of R-symmetry based pulse sequences for recoupling of 13 C/ 15 N CSA interactions that work well in both natural abundance and isotopically enriched systems. We demonstrate that efficient recoupling of either first-rank (σ 1 ) or second-rank (σ 2 ) spatial components of CSA interaction is attained with appropriately chosen γ -encoded RN n v symmetry sequences. The advantage of these γ -encoded RN n v -symmetry based CSA (RNCSA) recoupling schemes is that they are suitable for CSA recoupling under a wide range of MAS frequencies, including fast MAS regime. Comprehensive analysis of the recoupling properties of these RN n v symmetry sequences reveals that the σ 1 -CSA recoupling symmetry sequences exhibit large scaling factors; however, the partial homonuclear dipolar Hamiltonian components are symmetry allowed, which makes this family of sequences suitable for CSA measurements in systems with weak homonuclear dipolar interactions. On the other hand, the γ -encoded symmetry sequences for σ 2 -CSA recoupling have smaller scaling factors but they efficiently suppress the homonuclear dipole-dipole interactions. Therefore, the latter family of sequences is applicable for measurements of CSA parameters in systems with strong homonuclear dipolar couplings, such as uniformly-13 C labeled biological solids. We demonstrate RNCSA NMR experiments and numerical simulations establishing the utility of this approach to the measurements of 13

show abstract

Carbon-13 chemical shift anisotropy

Cited by 275 publications

References 60 publications

A solid-state ¹³C NMR and theoretical investigation of carbonyl and thiocarbonyl carbon chemical shift tensors

A solid-state ¹³C NMR and theoretical investigation of carbonyl and thiocarbonyl carbon chemical shift tensors

Asp⁸⁵ is the only internal aspartic acid that gets protonated in the M intermediate and the purple‐to‐blue transition of bacteriorhodopsin A solid‐state¹³C CP‐MAS NMR investigation

Recoupling of chemical shift anisotropy by R-symmetry sequences in magic angle spinning NMR spectroscopy

Contact Info

Product

Resources

About

Carbon-13 chemical shift anisotropy

Cited by 275 publications

References 60 publications

A solid-state 13C NMR and theoretical investigation of carbonyl and thiocarbonyl carbon chemical shift tensors

A solid-state 13C NMR and theoretical investigation of carbonyl and thiocarbonyl carbon chemical shift tensors

Asp85 is the only internal aspartic acid that gets protonated in the M intermediate and the purple&#x2010;to&#x2010;blue transition of bacteriorhodopsin A solid&#x2010;state13C CP&#x2010;MAS NMR investigation

Recoupling of chemical shift anisotropy by R-symmetry sequences in magic angle spinning NMR spectroscopy

Contact Info

Product

Resources

About

A solid-state ¹³C NMR and theoretical investigation of carbonyl and thiocarbonyl carbon chemical shift tensors

A solid-state ¹³C NMR and theoretical investigation of carbonyl and thiocarbonyl carbon chemical shift tensors

Asp⁸⁵ is the only internal aspartic acid that gets protonated in the M intermediate and the purple‐to‐blue transition of bacteriorhodopsin A solid‐state¹³C CP‐MAS NMR investigation