Solvation state of the Tyr side chain in peptides. An FT-IR and 17O NMR approach

Abstract

Detailed studies of the 17 O NMR chemical shifts of the COH group of p-cresol and tyrosine derivatives as a function of pH and in a variety of solvents revealed an unusually large titration shift upon the deprotonation of the phenol group and a very small chemical shift variation as a function of solvent hydrogen-bonding ability. Similarly the ν CO stretching frequencies exhibit a very small variation as a function of solvent hydrogen-bonding ability, and discrete hydrogen-bonded species could not be identified