Random-coil chemical shifts of phosphorylated amino acids

The H-1, C-13, N-15 and P-31 random-coil chemical shifts and phosphate pK(a ) values of the phosphorylated amino acids pSer, pThr and pTyr in the prote cted peptide Ac-Gly-Gly-X-Gly-Gly-NH2 have been obtained in water at 25 deg rees C over the pH range 2 to 9. Analysis of ROESY spectra indicates that t he peptides are unstructured. Phosphorylation induces changes in random-coi l chemical shifts, some of which are comparable to those caused by secondar y structure formation, and are therefore significant in structural analyses based on the chemical shift.