The principal values of ^1^3C chemical shift tensors in powdered L-tyrosine were measured by a newly developed Triple-echo two-dimensional magic angle turning (MAT) experiment. Theoretical results obtained by using the gauge invariant atomic orbitals (GIAO) ab initio method are basically in agreement with the observed values. It is shown that in complex system like L-tyrosine, using a locally dense basis set with a large number of atomic basis functions for the carbon atom of interest and smaller sets of atomic functions for the other atoms can not only save the disk capacity and computing time but also produce satisfactory results.

Key words: TYROSINE, CHEMICAL SHIFT, AB INITIO CALCULATION