4 ms·

It would seem to me some laws of thermodynamics would prevent any such "infection"-style reaction, but I am not a physicist nor chemist.

• tomrod 5y ago
  There is some debate in a certain context: https://www.youtube.com/watch?v=p_8yK2kmxoo https://www.youtube.com/watch?v=p_8yK2kmxoo Entertaining too!
• sp332 5y ago
  Supercooled water shows this kind of reaction with normal ice.
  • nawgz 5y ago
    Right, but that "supercooled water" can only make such a reaction because, thermodynamically speaking, someone intentionally injected energy into it without changing its state, thus enabling the reaction to occur within the bounds of the energy delta created, and ending when that ends. I do not see how a molecule could be stable in some condition, and then when making contact with something else, result in nothing other than a cascading state-change of that other. It doesn't make sense.
    • rocqua 5y ago
      The issue occurs if the new state is inherently lower energy. This is already the case with prions.
      • nawgz 5y ago
        I am not under the impression folding proteins is a state-change, and it's also unclear to me if it is a chemical reaction, so I do not think I understand the relevance of this point. I specifically stated the parameters.
        • sp332 5y ago
          It's not a chemical change. Neither is ice forming from water.
          • nawgz 5y ago
            Yes, clearly ice <-> water is a state change and not chemical, but my point is mostly that prions / protein folding is neither a state-change nor a chemical change, so I don't see how it's relevant to the posited scenario.
            • beecafe 5y ago
              A prion causing other proteins to misfold can only occur if the misfolded state has lower energy than the correctly folded one. It does this by acting as a catalyst, lowering the potential energy barrier that was allowing the protein to persist in the correctly folded state, to the point where e.g thermal fluctuations allow it to cross that barrier. The equivalent could occur if there was a lower energy state for water (and an ice-9 like scenario could then occur if this lower energy state catalyzed further transitions to this lower energy state). We don't expect this to be possible though, as we can't make water decay by other ways of making it cross that hypothetical potential energy barrier by dumping energy into it (whereas for a protein you can e.g burn it, denature it, etc), and aren't aware of catalytic activity by any forms of water.
              • nawgz 5y ago
                Thanks for the comment. Thinking out loud, for prions is not the requirement that they "[act] as a catalyst, lowering the potential energy barrier ... to the point where e.g thermal fluctuations allow it to cross that barrier" also a guarantee against this type of ice-9 "infection" scenario, because the equilibrium of the environment itself would be so impacted and be absorbing that energy and then causing unfavorable conditions to the reaction at the reaction's frontier even? I more-or-less equate that to the "supercooled water + normal ice" reaction of how much energy delta you can create allows you to make a small energy explosion reaction/state-change/etc that isn't truly an "infection" but just a localized energy transfer. But okay, after stating this very interesting mechanism in that form, I see the point being made by others. This catalyst-style mechanism which can induce physical changes in the environment without itself changing could be exploited on scales that would allow one to "maliciously/adversarially" create a chemical / energized substance that would catalyze say a lake or an ocean into freezing / sublimating. However, I find it impossible to see how such a transition could be found for water though, and it seems to me the nature of the prion & proteins is that the prion requires some level of complexity in the matter it interacts with to cause this energy transition. For more exotic substances than water, or perhaps water which itself holds a large amount of solutes satisfying some characteristic, I could see it. I appreciate your insight into this matter clarifying the prion mechanism especially. I am also not well educated on these matters so hopefully it doesn't stink too bad :)
      • jschwartzi 5y ago
        Just a nitpick but the process of crystallization evolves energy rather than involves. So it’s proceeding to a lower-entropy state. If we wanted to trigger such a transformation we’d have to involve machinery so you’re right in that sense. But there are other ways in which the universe stumbles into lower-entropy states sometimes, including crystallization from a super-saturated solution. Super-saturation could be driven by something as simple as the day/night cycle