Western Blot - Input vs IP - (Nov/18/2010 )

Hi there

Regarding western blots, what is the difference between the input and the ip/co-ip?

I know the input is for detecting cell expression and that ip/co-ip is for detecting proteins, and protein-protein interaction...but I cant wrap my head around how they are different. The same samples are involved in both the input and the ip/co-ip but as far as what I have been doing, the only difference is the beads for the ip/co-ip. Would greatly appreciate it sooooo much if someone could shed some light for me!!!!

Thank you sooo much in advance!

Generally you only differentiate between the input and the ip lanes when you are doing an immunoprecipitation, so if you don't do an immunoprecipitation, everything is input, you just don't necessarily call it that. So basically the input is the total protein lysate and what is eluted from the beads after the immunoprecipiation is the immunoprecipitate (the "IP"). So only proteins that bind to the antibody (and the proteins that bind that protein...hence the CO-ip) will be in the IP. Does that make sense?