I need a good blocking buffer for my chemiluminescent EMSA. The kit I started with will not tell me what is uses in the blocking buffer. I no longer need the kit except for the blocking buffer, and $300.00 per 500 mls is alot to pay. I am using biotinylated target, running it out on a native 7.5% Acrylamide gel and transfering it to a positively charged nylon membrane and then using a SA-HRP conjugate, and developing with a chemiluminescent substrate. All is working well, but I need a good blocking buffer.

The only suggestion (which i'm sure you've received by now) would be to try out different combinations of DNA and protein spp blocking agents (e.g. salmon sperm DNA+fish skin gelatin OR milk powder OR BSA) across multiple strips of your nylon membrane (each with one lane loading with exactly the same amount of your positive control).