I know that some companies (I remember Roth in particular) sells protein-free blocking agents for Western. I never tried them though, and I dont know if they'd let you know what it is made of.... Hope this helps, Ina -- Ina Hinners ICRF Secretory Pathways Laboratory 44 Lincolns Inn Fields WC2A 3PX London UK email: I.Hinners at icrf.icnet.uk