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Hi, Phosphate + calcium - not an easy combination :) Fluka brand PEGs used to be the way to go. I would carefully test the pH of the actual solution in the kit, and compare it with the pH of the solutions you're making yourself. There are several reasons as to why - but these values aren't always the same which (in my experience) is responsible for 40-50% of cases when screening conditions do not reproduce. Old PEG solutions can go very acidic, for instance - see previous CCP4bb exchanges on this subject. Good luck! Artem > Hello, > > I am trying to reproduce two hits obtained from the PEG/Ion screen of > Hampton which showed up with 20% PEG3350 and 0.2M K2HPO4/0.2M CaCl2. I > tried optimizations making up my own solutions with the two salts from > Sigma > (The PEG is from Hampton). To my surprise, the hits do not translate > during > optimizations. I am suspecting the salts. My question is, what grade of > Sigma > chmicals would be equivalent to the ones sold by Hampton? > > Any other suggestions would be more than welcome. > > Regards > Hari >