Circular dichroic (CD**) spectra of octopus vulgaris (Japanese form) hemocyanin were measured over a wavelength range of 210 to 700mμ in the forms of oxy-, deoxy- and apo-hemocyanin. Oxyhemocyanin showed three bands in the visible region (a positive band above 700mμ, a negative band at 570mμ, and a positive band at 450 mμ), a large negative band at 350mμ, several positive maxima in the ultraviolet region and a negative trough at 222 mp. In the CD spectra of deoxy-and apo-hemocyanin, characteristic three bands in the visible region and a large band at 350 mp completely disappeared, but the bands in the ultraviolet region still remained. A little change in the CD spectrum was observed in the ultraviolet region on oxygenation of deoxyhemocyanin.
