Nearly all organic material (like bacteria and viruses) is destroyed at temperatures above 60° Celsius. Some temperature resistant pathogens can survive slightly higher temperatures than this, but even the most hardy will be destroyed at temperatures above 150° Celsius.
But for prions these temperatures are hardly sufficient. They can survive being frozen, cooked, steamed, and even chemically treated with substances like formaldehyde and alcohol. Temperatures as high as 600° Celsius will not reliably kill them, and only in the 1000° Celsius range are they destroyed. At this temperatures, most *metals* will melt.
Why are prions so hard to destroy if they are chemically identical to the organic material inside our body already?
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This actually sent me into a heavy deep dive, and so I’ll drag you in. We’re going to jump around a bit, but we’ll come back to prions toward the end. Chemistry happens first.
Prions are, quite simply, a protein that has misfolded. They’re typically isomers of a regular protein.
Isomers, put plainly, are differing molecules with the same chemical composition, but different structures. Chirality is a type of isometry where a molecule ends up mirrored but is otherwise chemically identical. An example of this is L-methamphetamine, which is literally methamphetamine but mirrored. It doesn’t have the same biological effect because the different geometry doesn’t let it bond to cell chemoreceptors.
If you’re having a hard time picturing this, imagine a North American wall outlet. Two parallel prongs with a centered bottom ground prong, but the prong on the right is smaller than that on the left, so you wouldn’t be able to plug in a mirrored (chiral isomer) plug.
Similarly, if you bent the prongs on a normal plug, it might be chemically identical with the same makeup as the undamaged plug, but it’s not going to fit. You’ve made a nonchiral isomer.
Pivoting back to proteins, they interact with each other and with cells by **nature** of their shape. The placement of certain atoms in a protein molecule is what allows it to bond with cells, with other molecules, and so on. That’s actually how a lot of medications work. The drug has a small area that is shaped the same as the area that a natural protein bonds with, and it can interface with those receptors.
And proteins themselves are just singular molecules. *Huge* molecules, very long and string-like, and the actual folding is caused by some areas of the molecule having a net positive or negative charge and attracting other areas of the molecule. Still following along?
“Denaturing” is what we tend to refer to as proteins “breaking down” but it’s more accurate to say that it’s the process of a protein losing its shape. Increasing temperature means that electrons can get excited and bump up to different orbitals of their atom, which means those local charges that keep areas close together move around and you lose that bond. When the molecule cools back down, it can form different shapes as different areas bleed off energy and have their electrons drop into lower orbitals, causing different local charges. The protein “misfolds” and since it can no longer interface with receptors in the same way, it’s effectively dead. Denatured. (Acids and bases can technically denature proteins, as does ethanol, but in those cases it’s not that different a process. Strong ions in the solvent have a stronger attraction to those charged areas of the molecule than the internal charge bonds, and then the protein misfolds when the solvent is removed.)
Prions are bad proteins. Misfolded for whatever reason, they can interface with cell receptors. That said, they don’t interface in the right ways. Either they interface incorrectly, or they interface with the wrong kind of cell. And by doing so, they can cause other proteins to be misfolded or mismanufactured by cells.
And that might tip you off to the problem.
The reason heat or acid or base or alcohol or bleach kills cells is that it causes the proteins to denature. That’s why it’s relatively easy to kill cells and viruses. They fall apart.
But prions? They’re already the result of denaturing. You can do it again, but it will still be a misshapen protein at the end.
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