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I am trying to find out what the energy gain from hydrolysis of DMSP (Dimethylsulfoniopropionate) is, versus the energy gain from oxidation of a sugar or carb (e.g. glucose) in a terrestrial atmosphere.

To be clear, I am talking about the 'cleavage of chemical bonds by the addition of water' to DMSP.

This question is motivated by the issue of whether heterotrophic animals living in a reducing atmosphere of an exoplanet which has no free atmospheric oxygen might use DMSP or some similar compound for energy storage in preference to carbohydrates.

DMSP was mentioned by the paper linked below, which suggests that ocean algae get energy from this process and so could alien metabolisms which don't have access to O2. The author states that the energy available from hydrolysis of DMSP is the same in a reducing or oxidising atmosphere but doesn't state what that energy gain actually is in j/mol.

I realise the actual energy storage molecular species used by an actual organism on such a planet is probably going to be something else, but this seems like a good proxy.

"Photosynthesis in Hydrogen-Dominated Atmospheres", William Bains, Sara Seager and Andras Zsom

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    $\begingroup$ Some places your question refers to "hydrolysis" and other places "reducing DMSP with free hydrogen". You need to decide what reaction you are really interested in. I answered based upon the "cleavage" reaction, which is occurs on Earth. If you are really interested in a different reaction the answer would be different. $\endgroup$
    – DavePhD
    Oct 20, 2015 at 15:47
  • $\begingroup$ Yes I see your point and have identified my source of confusion. I will edit the question to clarify. $\endgroup$
    – rumguff
    Oct 21, 2015 at 22:04
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    $\begingroup$ Would you accept theoretical data from a QC program such as Gaussian? $\endgroup$
    – gsurfer04
    Oct 22, 2015 at 0:22
  • $\begingroup$ @gsurfer04 - yes I would as long as you can clarify the results in some kind of laymans terms and provide a link to recreate the results (assuming of course the program is open access). $\endgroup$
    – rumguff
    Oct 22, 2015 at 10:03
  • $\begingroup$ @rumguff I edited my answer to make it more clear. If it doesn't answer the question clearly, please let me know. $\endgroup$
    – DavePhD
    Oct 23, 2015 at 12:38

1 Answer 1

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When the literature refers to "hydrolysis" of DMSP, it is referring to the following cleavage reaction, even though no water is involved in the overall reaction:

DMSP --> DMS + acrylate + H+

See for example at page 156 of Biological and Environmental Chemistry of DMSP and Related Sulfonium Compounds: "hydrolysis of DMSP to DMS and acrylic acid".

For the above reaction:

$\Delta G = -11.8$ kcal/mol

Source: MetaCyc Reaction: 4.4.1.3

This means 11.8 kilocalories (49.4 kilojoules) of energy are released for each mole of DMSP that reacts.

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