13C and (15)N chemical shift tensors in adenosine, guanosine dihydrate, 2'-deoxythymidine, and cytidine.
The (13)C and (15)N chemical shift tensor principal values for adenosine, guanosine dihydrate, 2'-deoxythymidine, and cytidine are measured on natural abundance samples. Additionally, the (13)C and (15)N chemical shielding tensor principal values in these four nucleosides are calculated utilizing various theoretical approaches. Embedded ion method (EIM) calculations improve significantly the precision with which the experimental principal values are reproduced over calculations on the corresponding isolated molecules with proton-optimized geometries. The (13)C and (15)N chemical shift tensor orientations are reliably assigned in the molecular frames of the nucleosides based upon chemical shielding tensor calculations employing the EIM. The differences between principal values obtained in EIM calculations and in calculations on isolated molecules with proton positions optimized inside a point charge array are used to estimate the contributions to chemical shielding arising from intermolecular interactions. Moreover, the (13)C and (15)N chemical shift tensor orientations and principal values correlate with the molecular structure and the crystallographic environment for the nucleosides and agree with data obtained previously for related compounds. The effects of variations in certain EIM parameters on the accuracy of the shielding tensor calculations are investigated.
Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, USA.
Dirk
D
Stueber
David M
DM
Grant
D000241:Adenosine / Q000737:chemistry*; D002247:Carbon Isotopes; D003562:Cytidine / Q000737:chemistry*; D006151:Guanosine / Q000737:chemistry*; D015394:Molecular Structure; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular; D013936:Thymidine / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D014867:Water; D006151:Guanosine; D003562:Cytidine; D000241:Adenosine; D013936:Thymidine