Hi everyone,

I have been trying to crystallize Fab:antigen complex( 50kda:90kDa) complex and initially got needle clusters which after microseeding gave me single crystals but they are very small and I could not repeat the results. I have been using HEPES buffer at pH 6.8 to do the final SEC purification step of the complex before setting trays.

I was wondering whether there are some other buffers (that one could suggest eg tris-hcl etc) which have given decent positive results when crystallizing Fab complexes.Though I have gone through individual papers (case by case) to get some idea, It would be great if anyone could direct me to a comprehensive literature towards studying the crystatllization conditions of Fab complexes.

 Equally, people who have considerable experience could suggest a list of must do steps for such problems which have routinely been practiced in their lab

Also what is a good storage condition for the excess complex that you want to use later?

I would really appreciate any suggestion,help, direction.

Thanks 

ivan