comment by Fluttershy ·
2015-05-19T06:10:07.962Z · LW(p) · GW(p)
Epistemic status: unlikely that my proposal works, though I am confident that my calculations are correct. I'm only posting this now because I need to go to bed soon, and will likely not get around to posting it later if I put it off until another day.
Does anyone know of any biological degradation processes with a very low energy of activation that occur in humans?
I was reading over the "How Cold Is Cold Enough" article on Alcor's website, in which it is asserted that the temperature of dry ice (-78.5 C, though they use -79.5 C) isn't a cold enough temperature to store cryonicists at long-term. The article is generally well written, and the calculations are correct, with one partial exception that I'll point out in a minute.
Specifically, the article says that:
I am going to be pessimistic, and choose the fastest known biological reaction, catalase. I'm not going to get into detail, but the function of the enzyme catalase is protective. Some of the chemical reactions that your body must use have extraordinarily poisonous by-products, and the function of catalase is to destroy one of the worst of them. The value for its E is 7,000 calories per mole-degree Kelvin.
However, for computing k(T1)/k(T2), i.e. the ratio of rate constants at different temperatures, the pessimism behind the assumption that E = 7000 cal/mol*K may be causing Alcor to incorrectly conclude that dry ice can't be used for cryopreservation. We can perform a manipulation of the Arrhenius equation, similarly to what is done in Alcor's post:
k[T1]/k[T2] = exp(-E/R(1/(T1) - 1/(T2)))
Where T1 is 310.16 K (37 C), T2 is the temperature of corpse storage (such as 194.66 K), E is the activation energy, R is the ideal gas constant, and k(T1)/k(T2) is the rate of a chemical reaction at T1 divided to the rate of the same reaction at T2.
One can see that the ratio of rate constants at different temperatures, k(T1)/k(T2), should increase by a factor of [k(T1)/k(T2)^(new rate constant value/old rate constant value)] if a rate constant value of something other than 7000 cal/mol*K is used for E. So, if the fastest biological degradation process which humans experience at the temperature of dry ice has an activation energy of, say, 21,000 cal/molK, then, since the k(T1)/k(T2) calculated with E = 7,000 cal/mol\K is equal to 844.4 at the temperature of dry ice, the k(T1)/k(T2) calculated with E = 24,000 cal/mol*K at the same temperature would be 844.4^(21,000/7,000) = 844.4^3 = 6.02 * 10^8.
This means that the amount of degradation a person on dry ice's body should experience over 6.02 * 10^8 seconds, i.e. 19 years, would be equivalent to the amount of degradation that person would experience after 1 second at room temperature, given the completely hypothetical changes in activation energy stated above.
Of course, the number I got above was only as large as it was because I was seeing what happened if the activation energy tripled. Hence my reason for asking if anyone knew of any biological degradation processes with a very low energy of activation.
There may be assumptions which the Arrhenius equation makes which I'm not considering here, i.e. the assumption that fast mixing is occurring, and the assumption that the activation energy is constant across a wide range of temperatures.