Chemical shift tensors: Theory and application to molecular structural problems

摘要

The development of fast and accurate methods to calculate 13C and 1H NMR chemical shifts using purely empirical models provide extremely fast calculations that are useful for high throughput studies. The high speed of chemical shift calculations is achieved using a simple structure description scheme based on individual atoms rather than functional groups. The Torsion Angle Likeliness Obtained from Shift and Sequence Similarity (TALOS) approach is based on the observation that the chemical shift in proteins depends strongly on the local structure. It can predict the backbone angles of 88.5% residues with a standard deviation of 5.5%. The development of effective Density Functional Theory (DFT) methods that include electronic correlation effects has proved to be an important tool in the field of shielding calculations. Using the DFT theory, which scales as N2, it is possible to calculate shieldings in molecular systems of practical interest including electronic correlation effects.