The distributions of metal ions in rabbit metallothionein (MT) and its protein band in sodium dodecyl sulfate-polyacrylamide gel after electrophoresis were determined by synchrotron radiation X-ray fluorescence (SRXRF) analysis. Results showed that MT-1 mostly contained zinc
which amounted to 97.9% of the total metallic content and MT-2 mainly contained zinc and cadmium. This paper also introduced the method to determine the relative amounts of protein-bound metal ions in situ by combination of electrophoretic separation and SRXRF analysis.