For the extraction of type IV collagen, the normal placenaes at term were placed under pepsin digestion (once).

To purify the extracted collagen, Saltingout and changing the PH were performed (each step twice).

All steps of the extraction and purification were controlled by the SDS-PAGE electrophoresis and finally purified collagen with molecular weight 170 and 185 KD chains were obtained. The electrophoretical patterns of collagen chains were compared with the standard collagen from Sigma.