I have a huge amount of information I can recall from memory, especially for one my age, but it is not always without corruption, so I decided to check what I said about how prions increase in number (There are no errors in what I said from memory). This recent text is quite good description of prions:
Prions: Not alive but they can evolve - News: Cell Biology December 31, 2009
"... Prions are mostly protein. Although protein is a fundamental component of living cell material, prions are not alive. They behave something like viruses, without DNA or RNA yet able to reproduce by forcing living cells to do the reproduction for them. Prions were hypothesized in the 1960’s (Alper and Griffith) but not discovered until 1982 by Stanley Prusiner (for which he received the Nobel Prize in 1997). Like the role of proteins in epigenetics (adaptation or change in gene expression not caused by DNA), the more molecular biologists dig into proteins the more versatile and important they become. New research shows that includes the ability of prions to evolve.*
Prions are chains of proteins (polymers) that exist in many cells in a native harmless form. There are also infectious prions, from which the name is derived (
proteinaceous infect
ion). The infectious prions force normal prions to assume a misfolded shape, thereby reproducing the infection. In the misfolded shape, called an amyloid beta sheet, prions are very stable. The stability lets them accumulate in infected tissue, eventually causing tissue damage and cell death. This is the basis of some very nasty illnesses such as bovine spongiform encephalopathy (mad-cow disease) and Creutzfeldt-Jakob disease in humans. All known prion diseases are incurable and fatal. ..." From:
http://scitechstory.com/2009/12/31/prions-not-alive-but-they-can-evolve/
Read more of this text to see why they say prion, although not alive can adapt (or evolve) to a changed environment. This adaptation is not any change in stored information - the prion has none - no DNA etc. The adaption is more like isolated water molecules at low temperature, joining together as the temperature is lowered and eventually forming a solid or a liquid.
I.e. an ordinary water molecule, H2O, is polar with both protons (Hs) on the same side of the negative -O- (With angle of 105 degrees between the two Hs). As water is cooled, polymer chains develop. I.e. water at 4 C or lower is nH2O molecules where "n" is some small integer and n = 1 becomes increasingly rare as 0 C is approached.
I´ll represent the polar isolated H2O molecule by (+2H,-O-). As the temperature cools, you get electrostatically bound chains like:
(+2H,-O-)(+2H,-O-)(+2H,-O-)(+2H,-O-) ... (+2H,-O-)(+2H,-O-)
These chains have some flexibility - are not linear as I illustrated, but sort of like a bowl full of half cooked spaghetti with voids between the tangle of chains. As temperature drops below 4C, which is the densest state of water, the typical value of n increase, i.e. the typical chain grows longer, and the void volume steadily increases.
Thus, in the same sense as this article does, one can say: "Water is not alive, but does evolve" (with changing environment).
* This "evolution" or joining together of individual prion molecules to form even more stable units is well illustrated in this short video:
http://www.professorcrista.com/files/animations/posted animations/prions_characteristics.html
It is important to note that this "evolution" of both water and prions is NOT any change in the information they contain - A million years from now prions and water will be exactly like they are today - doing the exactly same joining together ("adaptation" or "evolving") as the environment changes they do today - no new creature will ever evolve from either water or prions. They do not do that Darwinian type of "evolution" that life forms do.
If you want to say "prions are alive," then you must say that about water too. The article, in the title even, clearly states prions are NOT alive.
My main** criticism of these articles is they fail to point out, as I did, that the non-prion folding of the same molecule MUST first be given a little energy (the activation energy) to at least partially unfold it before it can refold into the prion shape. I.e. If the environment is cold, the prion can not change the shape of the non-prion molecule to the shape of a prion, as the collision between it and a prion lacks the "activation energy." Article I read some years ago, noted this fact.
** I also don´t like the articles´s occasional calling of the non-infectious folding of the same chemical compound a "normal prion" - IMHO, it is better, less likely to confuse, to reserve "Prion" only for the infectious foldings and just call the other foldings of the same chemical compound just that; or more completely: "non-infectious foldings of the same protein, a particular chemical compound, as the infectious prion folding is." (But I can see why only two words were used instead.)
In contrast to prions, virus are very definitely alive. They do contain information that can "Darwinian evolve" under natural selection. - If you don´t believe that, just stop taking your anti-biotic immediately when your sickness is over. ToE applies to viruses but not to prions. Although Darwin did not know it, ToE is all about AND ONLY ABOUT, how stored information in a group of living creatures changes with time. No individual molecule stores any information so ToE, a theory about how stored information change in living forms, does apply to prions.