In order to develop and apply the silk sericin protein in functional polymeric materials

the co-ordination reaction of sericin with copper(Ⅱ) ion in aqueous solution is studied by measurements of pH titration and optical spectra

and the coordination structure of the formed complex at high pH as well as its higher order structure are investigated by electron spin resonance(ESR) spectra and X-ray diffraction. When the pH value is over 9.1 or so

each Cu2+ consumes about four OH- ions

and the optical absorption band lies at 540nm

which indicate that the type of Cu2+-protein biuret complex is formed.And the ESR spectrum shows that the unpaired electron of copper(Ⅱ) in the complex localizes in the ground state of dx2-y2 orbit.So it is put forward such coordination structre as Cu(N)4(OH-)2

whose special structure is of stretchy octashedron.The X-ray diffraction pattern shows that the copper(Ⅱ)-silk sericin complex has an amophous structure of random coil.