Chemical shifts of backbone atoms in proteins are exquisitely sensitive to local conformation, and homologous proteins show quite similar patterns of secondary chemical shifts. The inverse of this relation is used to search a database for triplets of adjacent residues with secondary chemical shifts and sequence similarity which provide the best match to the query triplet of interest. The database contains 13Ca, 13Cb, 13C', 1Ha and 15N chemical shifts

The change in 13C' chemical shift when switching from an isotropic solution to a dilute liquid crystalline medium depends on the orientation of the chemical shift anisotropy (CSA) tensor relative to the molecular alignment tensor. The correlation between the observed change in 13C' shift and the one predicted by the protein's structure (Dd 13C') provides a sensitive monitor to evaluate the quality of the structure. Thus, a quality factor, Q, is defined

Isotropic and anisotropic chemical shielding, together with scalar and dipolar coupling, are NMR observables that contain information of key importance for protein structural studies. We present a database program (TALOS) that searches for triplets of adjacent residues with secondary chemical shifts and sequence similarity which provide the best match to the query triplet of interest. Tests carried out for proteins of known structure indicate that