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>Ab-inito Quantum Mechanical Calculations of NMR Chemical Shifts in Nucleic Acids Constituents II Conformational Dependence of thelH and13C Chemical Shifts in the Ribose
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Ab-inito Quantum Mechanical Calculations of NMR Chemical Shifts in Nucleic Acids Constituents II Conformational Dependence of thelH and13C Chemical Shifts in the Ribose
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机译：Ab-inito Quantum Mechanical Calculations of NMR Chemical Shifts in Nucleic Acids Constituents II Conformational Dependence of thelH and13C Chemical Shifts in the Ribose
The magnetic shielding constant of the different13C and13H nuclei of a deoxyribose are calculated for the C2#x2032; endo and C3#x2032; endo puckerings of the furanose ring as a function of the conformation about the C4#x2032;C5#x2032; bond. For the carbons the calculated variations are of several ppm, the C3#x2032; endo puckering corresponding in most cases to a larger shielding than the C2#x2032; endo one. For the protons the calculated variations of chemical shifts are all smaller than 1.3 ppm, that is of the order of magnitude of the variation of the geometrical shielding produced on these protons by the other units of a DNA double helix, with a change of the overall structure of the helix. The computations carried out on the deoxyribose #x2212;3#x2032; and 5#x2032; phosphates for several conformations of the phosphate group tend to show that the changes of conformation of the charged group of atoms produce chemical shift variations smaller than the two conformational parameters of the deoxyribose itself. The calculations carried out for a ribose do give the general features of the differences between the carbon and proton spectra of deoxynucleosides and nucleosides.
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