*** For details on how to be removed from this list visit the *** *** CCP4 home page http://www.dl.ac.uk/CCP/CCP4/main.html *** Xinqi: 5 mM should be enough for preventing free -SH forming s-s bridges. CAn ^Hyou ensure your protein aggregate due to the free -SH forming s-s bonds. How about trying the ICH2COOH which can react with the free -SH? Guan