Abstract
The pD dependence of chemical shifts of the methylene protons in glycine and glycinepeptides (up to tetraglycine) in D2O solution has been investigated by proton magnetic resonance spectroscopy. The different kinds of the methylene protons in glycinepeptides show different chemical shifts. Furthermore, their chemical shifts significantly depend on the pD of the solutions, and reflect the dissociations of the carboxylic and amino groups. The chemical shifts of the methylene protons in peptides in D2O solution have been determined in the pD region from ca. 1 to 14. In addition, the dissociation constants, pK1 and pK2, in D2O solution are estimated from the present results as follows; pK1=2.84 and pK2=10.84 for glycine, pK1=3.74 and pK2=9.34 for diglycine, pK1=4.04 and pK2=9.04 for triglycine, and pK1=3.94 and pK2=8.94 for tetraglycine.
