[pdonis]

> Proteins aren't destroyed by cooking. Otherwise you would not be able to get any proteins from cooked meat or beans.

"Protein" in food really means "amino acids" as far as nutrition is concerned; even if the protein isn't denatured by cooking (and at least some proteins are), it will be broken down to amino acids by your digestive system before being absorbed into your body. Your body uses the amino acids to build its own proteins.

[dualogy]

IIRC quite a few animal-source protein strings that are "fully compatible" with our own ('animal') bodies are taken up as-is without breakdown into AA and resynthesis into "human protein". Much more efficient.

[pdonis]

A representative sample of the current understanding is here:

http://www.ncbi.nlm.nih.gov/books/NBK22600/

"Proteins ingested in the diet are digested into amino acids or small peptides that can be absorbed by the intestine and transported in the blood."

If by "animal-source protein strings" you mean "small peptides", then yes. But in general they still have to be resynthesized into the proteins used by the body. There might be a few useful proteins that are small enough to fall into the "small peptide" range and would therefore be absorbed and used as-is.

Prions have a little over 200 amino acids, so they are on the large side to be considered "small peptides" (which AFAIK are typically a few to a couple of dozen amino acids). They appear to be resistant to the enzymes that normally digest proteins, and it doesn't appear to be clearly understood how they get from the digestive tract into the bloodstream. See, for example, here:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2538961/