The Chemical Shift Index method applied to resin-bound peptides.

ABSTRACT

The Chemical Shift Index (CSI) method proposed by Wishart et al. [Biochemistry (1992) 31, 1647-1651] to evaluate the secondary structure of peptides in aqueous solution uses as its reference the chemical shift values of each of the 20 natural amino acids (X) in a typical nonstructured sequence GGXAGG (17-20). In order to apply the CSI method to protected resin-bound peptides, we established a new database of chemical shift values for the same GGXAGG sequences in their protected form and anchored to a polystyrene resin swollen in DMF-d7. The predictive value of this new reference set in the CSI protocol was tested on different resin-bound peptides that were previously characterized by a full NOE analysis.