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Synthesizing Chemical "Life" Forms
ScienceDave | June 9, 2007 at 02:14 pmby
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I was first introduced to the concept of "life from chemistry" in my first year as an undergraduate. I was 17 years old, a budding anarchosyndicalist, and a staunch atheist (experience and wisdom have since taught me agnostics experience less flack, although equal amounts from both sides, while the majority of people unfortunately don't care what anarchists think). I was attending a community college in the heart of Canada's bible belt, and Stanley Miller's experiments were the day's topic. My professor asked everyone to stand up and head to one of four corners designated:
1) Life evolved from a primordial soup
2) Life was created by a power outside the universe
3) Life might have been created by a higher power, but it can't be proven
4) Life might have evolved from a primordial soup, but it can't be proven
I quickly stood up, and confidently walked to camp (1). There were 6 of us there, out of a class of 50. I was stunned, but what was more surprising, given the region's history, is that there were only two individuals in camp (2). What did I learn from this exercise? The fundamental principle of the scientific method: we know what we know through experience, nothing more, and can explain our surroundings to the best of our ability, only with what we know, right now. At the end of class, I left humbled.
What does this have to do with creating life through chemistry? Well, a recent report in the Proceedings of the National Academy of Sciences has demonstrated, using a chemical computer simulation based on previous observations, how certain molecules can "evolve" into more complex molecules. This is a fundamental paradigm to the origins of life, as most definitions of "life" require increased complexity and organization than the chaos of equilibrium chemical dynamics would allow.
The basic idea is that simple principles of chemical interactions allow for a kind of natural selection on a micro scale: enzymes can cooperate and compete with each other in simple ways, leading to arrangements that can become stable, or “locked in,” says Ken Dill, PhD, senior author of the paper and professor of pharmaceutical chemistry at UCSF...
...Like these more obvious processes [i.e. organisms evolving], the chemical interactions in the model involve competition, cooperation, innovation and a preference for consistency, they say.
What exactly gets "locked in"? Well, imagine two molecules, each of which has the ability to convert one chemical into another. These two molecules will be called Complex A and B, while the chemicals they convert will be referred to as A and B, respectively. Lastly, Complex A converts chemical A into chemical B.
This part is key, and forms the basis for Dill's model. As Complex A converts chemical A into B, Complex B will be ever-so attracted to complex A since it produces the chemical it is favoured to react with. Over time, as different forms of Complex A and B randomly form, the forms of these complexes that favour a close partnership between the two will be favoured since they would speed up the reaction. Eventually, a Complex AB will form.
And thus, Dill argues, increased complexity can be achieved in the world of chemistry.
“A major question about life’s origins is how chemicals, which have no self-interest, became ‘biological’ -- driven to evolve by natural selection,” he says. “This simple model shows a plausible route to this type of complexity.”
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