An ab initio quantum chemical investigation of TOMS nmr SHIELDING TENSORS IN Adenine-thymine, Adenine-uracil, Guanine-Cytosine & uracil-quartet: comparison between theoretical and experimental results

We have evaluated the NMR shielding tensors for A:T,G:C,A:U in Watson-crick, and U-quartet. We have computed NMR shielding tensors at B31YP level by using 6-31G(d) basis set. We have compute anisotropy and asymmetry in A:T,G:C,A:U and U-quartet. The NMR shielding tensors were calculated using the GIAO method.
The natural bonding orbital analysis (NBO) were performed. NBO calculation have been done at B31LYP level. We have evaluated lowest occupancy orbitals, highest energy, donor and acceptor atoms, core and valence orbitals, total Lewis, natural population in atoms in NBO calculation.