Dynamics of a proline-rich glycoprotein from human parotid saliva: a 360-MHz proton nuclear magnetic resonance investigation

The 360-MHz proton n.m.r. spectra of a proline-rich glycoprotein from human parotid saliva (PRG) were obtained in order to analyse spin-lattice relaxation (T₁) times and hydrogen-deuterium exchange rates. The (T₁) values for the proline ring and bulk peptide backbone C^αH^α protons were found to be about 0.5 s. The HåD exchange data revealed that only four of the many N-H resonances remained after the first few minutes of exchange. Within 96 h at 12°C most of the remaining peak intensities were gone. These data imply a dynamic conformation with a majority of the backbone free of hydrogen-bonded structures.