Controls for co-immunoprecipitation - (Mar/25/2013 )
Controls could be no antibody, non-specific (i.e. not one you expect to show interaction), serum from the animal(s) the antibodies were raised in, transfected and untransfected cells...
Just to add one more, if you have these genes knocked out in a particular genotype, antibody treatment with these make for great negative controls. I also believe for this type of work, knockdown controls are also useful with siRNA