AbstractThe solid‐state conformation of copolymers of oxidizedL‐methionine [L‐Met(O)] withL‐methionine (L‐Met) and/orL‐alanine (L‐Ala) was studied by IR spectroscopy and circular dichroism (CD). The results from the IR spectra in the region of 900−330 cm−1are compared with data obtained by CD experiments. A film cast from the solution of a copolymer containingL‐Met(O) had a new trough between 205 and 210 nm in the solid‐state CD spectra and new IR absorption bands at 815 and 680 cm−1, while oxidizing the film of anL‐Met containing copolymer after casting did not induce a significant change in IR and CD spectra. It seems that the film cast from the solution of anL‐Met(O) containing copolymer exhibits the feature of a random coil as well as of an α‐helix. From the CD spectra of the film on immersion in water, it was deduced that the helix of the film became gradually disordered and hence t