I have been unable to blog for the past few days because I was busy moving to Chapel Hill for a postdoc at UNC Chapel Hill. I am very excited about this move and my upcoming research which is going to involve protein design and folding. Regular blogging will resume soon. Until then, happy holidays, and I will leave you with the following interesting paper published by a group from my new institution.
One of the abiding puzzles in the origin of life is to explain how life arose in the relatively small amount of time it had to evolve on the planet. From a chemical perspective, this entails explaining how especially slow chemical reactions could have contributed to the complexity of life. In a new paper in PNAS, a group from UNC suggests part of a possible solution to the puzzle by demonstrating that slow reactions especially are accelerated by temperature much more than fast reactions. Recall from college physical chemistry that the rate of a typical reaction roughly doubles with ten degree rise in temperature. As the authors note, this bit of textbook wisdom is off the mark when it comes to many important reactions and needs to be appended.
They look at certain important reactions like the hydrolysis of phosphate monoesters and find that these reactions are accelerated not two or a few fold but many million fold with a rise in temperature. The increase in rate would have been significant especially under the hot, primordial conditions present on earth during its early days. Now this acceleration is free-energetic and basically corresponds to a favorable change in either the entropy or the enthaply of activation. The authors measure both these variables and find that the crucial change is in the enthalpy. It's interesting to note that a favorable change in the enthalpy would entail forming stronger interactions including hydrogen bonds between substrate and enzyme, and this is exactly the kind of process you would imagine happening during the optimization of biomolecular interactions during evolution. In fact, recent research suggests that this process of optimizing enthalpy is also synthetically mirrored during drug discovery. The authors end by explaining why a catalyst that impacted enthalpy rather than entropy favorably would have had a selective advantage in rate acceleration as the environment later cooled (and entropy became unfavorable).
Amusingly, the paper has come under criticism from some unexpected quarters, from none other than folks from the infamous 'Discovery' Institute which is funded and run by creationists. In the view of these esteemed 'scientists', the paper provides no evidence that the slow reactions which were accelerated were in fact ones which were important during the origin of life. The DI crowd seems to have fundamentally misjudged the nature of origins of life research; it's more speculative than many other fields but still remains scientific. More importantly, the criticism seems to have completely missed the fact that the general hypotheses proposed by the authors- that all slow reactions could have been vastly accelerated by temperature on a hot primordial planet- is independent of the exact nature of these reactions which may or may not have contributed to life's origins. As usual, miss the forest for the trees.
Stockbridge, R., Lewis, C., Yuan, Y., & Wolfenden, R. (2010). Impact of temperature on the time required for the establishment of primordial biochemistry, and for the evolution of enzymes Proceedings of the National Academy of Sciences, 107 (51), 22102-22105 DOI: 10.1073/pnas.1013647107