The Chemical Shift Index method applied to resin-bound peptides

The Chemical Shift Index (CSI) method proposed by Wishart et al. [Biochemis try (1992) 31, 1647-1651] to evaluate the secondary structure of peptides i n aqueous solution uses as its reference the chemical shift values of each of the 20 natural amino acids (X) in a typical nonstructured sequence GGXAC C (17-20). In order to apply the CSI method to protected resin-bound peptid es, we established a new database of chemical shift values for the same GGX ACG sequences in their protected form and anchored to a polystyrene resin s wollen in DMF-d(7). The predictive value of this new reference set in the C SI protocol was tested on different resin-bound peptides that were previous ly characterized by a full NOE analysis.