Dear all dimer in AU average B factor 21 resolution: 1.78 each subunit shows 2 Tin atoms in the active site B factor for 2 tin in chain A 15 and 19 but B factor for other 2 tin in chain B 30 and 41 41 for tin which is between the 2 cysteine (photo attached) (occ: 0.25) this one which i am worry about ((because the average B factor for the surrounding amino acid is 20)) and 30 of the other one near phoshate (occ: 0.70) 1- i tried to change the occupancy or refine the occupancy for tin trying to reduce B factor (41) it works (reduced to 30) but it gives me a +ve peak what could i do to solve this problem?? 2- other trial to define charge for that tin HETATM 3241  SN   SN C   3       6.543  -2.139 -14.821  0.25 41.55          SN4+ but it was the same result. --- is this definetion for that charge is OK or it is not enough in PDB file --- is this way is understandable by phenix.refine? i mean does phenix differentiate in refinment between SN, SN2+ and SN4+?? N.B: protein soaked in DimethylTindiBromide Haytham Wahba Biochemistry UdeM Canada