Pressure-dependent 13C chemical shifts in proteins: origins and applications

Pressure-dependent 13C chemical shifts in proteins: origins and applications.

Pressure-dependent (13)C chemical shifts have been measured for aliphatic carbons in barnase and Protein G. Up to 200 MPa (2 kbar), most shift changes are linear, demonstrating pressure-independent compressibilities. CH(3), CH(2) and CH carbon shifts change on average by +0.23, -0.09 and -0.18 ppm, respectively, due to a combination of bond shortening and changes in bond angles, the latter matc...

Pressure-dependent C chemical shifts in proteins: Origins and applications

Calculation of 13C chemical shifts in rna nucleosides: structure-13C chemical shift relationships.

Isotropic 13C chemical shifts of the ribose sugar in model RNA nucleosides are calculated using SCF and DFT-GIAO ab initio methods for different combinations of ribose sugar pucker, exocyclic torsion angle, and glycosidic torsion angle. Idealized conformations were obtained using structures that were fully optimized by ab initio DFT methods starting with averaged parameters from a collection of...

2H Isotope Effect on 13C Chemical Shifts of Nitro-Benzo-9-Crown-3

Deuterium substitution on two ortho-substituted-OCH2-fragments in Nitro-Benzo-9-Crown-3 induces low frequency shifts, positive mnDCj, in all 13C NMR resonances which is an indication of the increased shielding in this crown ether. The magnitude of these shifts vary from 15DC7=716 to 54D<...

Substituent Effects on 13c Nmr Chemical Shifts in Dialkylaminophenylchlorophosphines

The relative chemical shifts and 2J(PC) coupling constants in the low-temperature limiting spectra of a series of Ph(R,N)PCl compounds [R = Me, Et, PhCH2, ‘Pr and c-Hex] differ for R = primary or secondary. For primary alkyl substituents, the more downfield signal exhibits a large, positive coupling and the more upfield resonance shows a small, negative coupling. These observations are reversed...