Peptide ranging from residue 229 to 240 of the Dl protein of Photosystem (PS) 11 was synthesized and Were used as candidates of calcium Fiuorescence and FTIR spectroscopy were used totest the conformation after lanthanide additions. FIuorescenee spectroscopy showed that the synthetic peptide provide binding site and that glutamic acids are lnvolved in lanthanide. binding Resolution enhancement tech combined with band curve fitting procedures to quamitate the FT1R special information from the am the relative areas of these component bands indicate that lanthanide anldeinduced induced a substantial decrease in of unordered structure and turns. while a corresponding increase in the amount of a helix and open loop was also observed This indicate that a relatively compact stfllcture of the synthetic peptide ls formed if lanthanides are applied The results may reflect on the physiological and binchemical funcfion of caleium in PSII including preventing Dl fromtrypsin digestion.