I want to ask about the structural integrity of protein molecules that are present in mammalian bodily fluids. My question is not about the detection or determining what type of mammal has left a "protein fingerprint", but rather about the proteins that are left. For how long can those proteins' structure stay without being compromised after being exposed to the outside world/environment? For how long can you test for these proteins before they are no more, if they actually lose their structure?