Parathyroid Hormone (PTH) Peptide (IMAGE) University of Toronto Caption The new method overcomes obstacles in designing D versions of complex helical peptides. Credit Michael Garton, University of Toronto Usage Restrictions credit the source License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.