Analysis of spin-labelled glycylglycine interactions with cupric ions

Summary Glycylglycine substituted with 4-amino-2,2,6,6-tetramethyl piperidineN-oxide on the carboxylic acid function was used as a ligand to complex cupric ions. In aqueous solutions, blue species, of low stability, were obtained. E.p.r. spectroscopy showed the formation of various complexes. At basic pH values, a paramagnetic signal is observed with A = 101 gauss and g = 2.16. The spectroscopic parameters are interpreted in terms of strong magnetic exchange between the spin-labelled ligand and cupric ions.