Site-specific modifications of proteins at their N-termini are provided. In particular, a chemical modification of proteins at their N-termini via a transamination reaction to form homogeneous adducts such as, the corresponding oxime derivatives is provided. Methods of making and using the adducts in radio-labelling, molecular imaging applications, and treatment of disorders such as cancer, Crohn's disease, arthritis, atherothrombosis and plaque rupture are also provided.