Random-coil chemical shifts of phosphorylated amino acids

The 1H, 13C, 15N and 31P random-coil chemical shifts and phosphate pKa values of phosphorylated amino acids pSer, pThr and pTyr in the protected peptide Ac-Gly-Gly-X-Gly-Gly-NH2 have been obtained in water at 25 degrees C over the pH range 2 to 9. Analysis of ROESY spectra indicates that the peptides are unstructured. Phosphorylation induces changes in random-coil chemical shifts, some of which are comparable to those caused by secondary structure formation, and are therefore significant in structural analyses based on the chemical shift.