Calcium salts are often present in the centre of all types of gallstones.Matrix proteins are known to be essential for biomineralization and may also be important in the formation and growth of gallstones.In the present work we employed pepsin in order to assess its capability to induce the formation of CaCO_3 in biological circumstances in vitro.The appearance and morphology of CaCO_3 crystals obtained from systems with and without pepsin were observed by FT-IR,XRD and SEM.The results showed that the pepsi...