You were talking about the usability of protein. Now we are getting into something similar the the Glycemic Index for carbs. With Protein, its similar. I has to do with bioavailability, i.e. how fully can that substance be assimilated, and how quickly. I haven't seen a chart in years, but I do know that beef is around 75% usable, with eggs being right up there on the top. I would suggest doing a search on the subject.
Do you know anything about the usability of raw protein versus cooked? Not that I want to go around eating raw chicken, but I'm curious to know if proteins in their natural state are more readily accepted by the body than those that have been denatured and mangled by the heat of cooking.