In The Field

Soup, meet sandwich.

I stopped in for a press briefing today on the origins of life. It’s one of the few talks I’ve seen at the American Society for Cell Biology meeting that had no cells in it whatsoever. One of the great questions of our time has been how complex molecules began to aggregate in meaningful ways and pitch forward into something that could be recognized as life. The Stanley Miller experiments helped establish the idea that some primordial soup gave rise to complex interacting organisms. But folks have recongized that in a vast sea – or even a small puddle, interactions wouldn’t be energetically favourable or concentrated enough to get anywhere. So, folks have proposed that early macromolecules were affixed to clay particles or bubbled through porous rocks that would compartmentalize interactions and provide substrate for advancing enzymatic reactions. Helen Hansma, who is a rotating program director for the National Science Foundation, has another idea and she was at ASCB presenting a poster on it.

While looking at a chunk of mica under a microscope one day, she noticed bits of organic gunk growing in between it’s flaky layers and thought, “Hey that would be a neat place for an organism to thrive.” Having spent years tuning atomic force microscopes to observe biomolecules on mica sheets, she knew how amenable the structure of mica is to interaction. Another clue had her hooked on the hypothesis. No one, she says, has ever adequately explained how cells first obtained potassium. All cells tend to keep potassium in and sodium out despite the vast majority of ions that would have existed in primordial seas would have been sodium. But when the nanometer thick sheets of mica separate they do so by breaking covalent bonds and sometimes releasing free potassium. In her vision of this prebiotic model, mechanical forces of water infiltrating mica sheets could produce energy to power little bioreactors for molecules that stick to the surfaces between. RNA, she says, seems somewhat amenable to binding the surfaces within. So Hansma has added to the soup paradigm, a sandwich!

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