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#1
Old 08-13-2006, 10:20 PM
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Why aren't prions denatured by heat?

at least this is my understanding. i've heard that mad cow disease cannot be eliminated by thoroughly cooking steak.

why is this the case, if in fact they are made of protein? is it just a very simple, sturdy molecular structure? whats the deal?
#2
Old 08-13-2006, 11:12 PM
ftg ftg is offline
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The meat is made of protein too. (And water and fat.)

Breaking down the prion in meat is easy to do at the right temps. You just won't have anything "meat-like" left.
#3
Old 08-14-2006, 08:49 AM
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Quote:
Originally Posted by ftg
The meat is made of protein too. (And water and fat.)

Breaking down the prion in meat is easy to do at the right temps. You just won't have anything "meat-like" left.
but wasnt a human variation of mad cow ----- jacobs disease (not going to try to spell the first part) being passed along in a tribe that did a ritual consumption of ashes from their ancestors? or is that not the actual story?
#4
Old 08-14-2006, 08:53 AM
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Preston, the fellow who wrote the book "the Hot Zone" on Ebola, also did one on prions that I can't recall the tritle of now. He cites papers that show prions withstanding unbelievably huge temperatures. If they're right (I don't entirely trust Preston, and haven't looked up his cites), then you'd damned near have to vaporize a steak in order to dissociate the prions, which themselves are relatively simple molecules. Preston says he doesn't even trust Bone Meal (the kind used as plant food) anymore.
#5
Old 08-14-2006, 09:25 AM
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Quote:
Originally Posted by misterW
but wasnt a human variation of mad cow ----- jacobs disease (not going to try to spell the first part) being passed along in a tribe that did a ritual consumption of ashes from their ancestors? or is that not the actual story?
No. You're thinking of Kuru, which was a disease found int he indigenous populations of Papua New Guinea who practiced Cannibalism.

Creutzfeldt-Jakob Disease the original version, was an inherited disease, and was additional passed on via tissue, and organ donations.

Variant Creutzfeldt-Jakob Disease, is acquire through eating contaminated beef, from cattle with Bovine Spongiform Encephalopathy, who probably got it from a sheep who carry a prion which cases a disease called Scrapie. Sheep carcases carrying Scrapie were probably added to cattle feed, and passed the disease.
#6
Old 08-14-2006, 09:38 AM
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Have prions actually been shown to exist? I had thought that they were still, at this point, theoretical.
#7
Old 08-14-2006, 09:53 AM
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Prions at Wikipedia, with structure pictures.
Prions being proteins, are denatured by heat. The trouble is that once things cool off they refold into infective configuration. To eliminate infectivity you have to break the peptide backbone, and that's a lot more resistant to heat than a protein's tertiary structure.
#8
Old 08-14-2006, 10:03 AM
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Quote:
Originally Posted by Earl Snake-Hips Tucker
Have prions actually been shown to exist? I had thought that they were still, at this point, theoretical.
Prions do exist - it goes without any debate. What is debated, is if they are really vector for Creutzfeldt-Jakob Disease. I seem to recall quite recent report that put some stir about that, but don't remember details. Somebody help with straight dope about current scientific knowledge on prions and CJD, please?
#9
Old 08-14-2006, 01:03 PM
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They can be destroyed by heat - it just takes a LOT of it, far more than you get through cooking. Think about it. If cooking destroyed proteins, your food would be just a blob of goo once it came out of the oven.
#10
Old 08-14-2006, 02:53 PM
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Quote:
Originally Posted by CalMeacham
Preston, the fellow who wrote the book "the Hot Zone" on Ebola, also did one on prions that I can't recall the tritle of now. He cites papers that show prions withstanding unbelievably huge temperatures. If they're right (I don't entirely trust Preston, and haven't looked up his cites), then you'd damned near have to vaporize a steak in order to dissociate the prions, which themselves are relatively simple molecules. Preston says he doesn't even trust Bone Meal (the kind used as plant food) anymore.
The book was "Deadly Feasts" which I read and then shelved. It struck me as alarmist when the jury was still out. But then, I do love a good pot roast, so my bias should be obvious.
#11
Old 08-15-2006, 06:34 PM
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Quote:
Originally Posted by Smeghead
They can be destroyed by heat - it just takes a LOT of it, far more than you get through cooking. Think about it. If cooking destroyed proteins, your food would be just a blob of goo once it came out of the oven.
well, i wouldnt expect cooking temperatures to DESTROY proteins, but i would expect them to change their shape, and therefore alter their ability to function. After all, enzymes in the body can be damaged by a high fever, and cooking temperatures far exceed that.
#12
Old 08-15-2006, 07:17 PM
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It all depends on your protein. Some proteins are very easy to denature and some are damn-near impossible. Two of my favorite proteins are Staph toxin and Botulism toxin. Lets say that they are both in your soup. You decide you are going to boil you soup a loooong time to get rid of the toxins by denaturation. You will successfully eliminate the Botulism toxin, the Staph toxin will still cause you to effectively eliminate the contents of your GI tract. It all has to do with the structure of the protein and each different protein has a different affifity for its shape and a different denaturation temperature.
#13
Old 08-16-2006, 05:21 AM
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prions

They have recently developed techniques that have shown evidence of being able to http://vir.sgmjournals.org/cgi/content/full/85/12/3805 surgical instruments that have shown to test positive for some prion diseases. This comes after several people werehttp://ehu.sbs.soton.ac.uk/priona.htm in the UK by using instruments used on people who were infected (at the time unknown) with a prion disease. Although they autoclaved all the instruments, a super high pressured high heat decontamination process, they believed that these instruments were safe to use again. Unfortunately they were wrong.

But these new decontamination procedures have proven only that these instruments don't have a detectable amount of the prion disease. To the best of my knowledge if any cranial procedure is done on a patient with known prion disease (thats after you find a surgeon with enough balls to even open the person up), then you're supposed to dispose of any contaminated equipment.
#14
Old 08-16-2006, 05:22 AM
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I don't link much....

They have recently developed techniques that have shown evidence of being able to decontaminate surgical instruments that have shown to test positive for some prion diseases. This comes after several people were infected in the UK by using instruments used on people who were infected (at the time unknown) with a prion disease. Although they autoclaved all the instruments, a super high pressured high heat decontamination process, they believed that these instruments were safe to use again. Unfortunately they were wrong.

But these new decontamination procedures have proven only that these instruments don't have a detectable amount of the prion disease. To the best of my knowledge if any cranial procedure is done on a patient with known prion disease (thats after you find a surgeon with enough balls to even open the person up), then you're supposed to dispose of any contaminated equipment.
#15
Old 08-16-2006, 09:52 AM
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Quote:
Originally Posted by bigbabysweets2000
I don't link much....
Well, you should do, those were some excellent articles, thanks for those cites.
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