Evolving Thoughts: The enzyme at the beginning

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Evolving Thoughts: The enzyme at the beginning

Postby Timothy Chase » Mon Mar 19, 2007 6:58 am

John Wilkins has a nice post on the identification of the structure of a ribozyme capable of joining together ("ligation") two pieces of RNA - which he points out may be an important key in understanding how the RNA world came to be.

He quotes from an article in order to emphasise the importance of this:

"Starting with a mixture of randomly synthesized RNA molecules and selecting for the desired properties, researchers are able to evolve RNA enzymes from scratch. In the Ellington lab, Robertson evolved the ligase ribozyme (called the L1 ligase) and determined which parts were critical for its function and which parts could be removed to create a 'minimal construct.'"

The post is here:

The enzyme at the beginning
Posted on: March 17, 2007 5:21 AM, by John S. Wilkins
http://scienceblogs.com/evolvingthought ... inning.php

Additionally, after describing four different views regarding the origin of life, he has the following to say:

"I personally do not think that these are mutually exclusive hypotheses. No chemical reaction involving nucleic acids will not have had something akin to 'metabolism' (in the sense of employing the latent energy of the source molecules and free energy of the environment, to maintain the reaction), but some sort of stable catalyst is needed to keep the reaction cycle from drifting into error. I do not think either came first, but rather they came together, and clays and other structured minerals may have had something direct to do with it. But knowing that a ribozyme can evolve very early on makes the crucial role of RNA more likely."

Seems accurate enough. In any case, we discovered a self-replicating ligase ribozyme as far back as 2002. Unfortunately it didn't have the exponential growth curve, and moreover, it was simply joining together two shorter sequences. Since that time we have discovered ribozymes capable of adding individual ribonucleotides, and if I remember correctly, exponential growth - but studies in this area continue.
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Postby Chris Hyland » Wed Apr 04, 2007 10:07 pm

I always think the origin of life research is a great example of what a young scientific field should be. They aren't claiming they've got it sorted they're actually conducting research. I know a lot of scientists that think it is a complete waste of time, yet the OOL people don't claim this a conspiracy to prevent their research. Not only that they've made a lot of progress in the past few years.
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Postby Timothy Chase » Fri Apr 06, 2007 4:46 pm

We keep making advances - so much that it is difficult to keep up with them.

John Wilkins posted another discovery just a few days back:

On etiobiology
Category: Creationism • Evolution • General Science
Posted on: April 3, 2007 6:03 AM, by John S. Wilkins
http://scienceblogs.com/evolvingthought ... iology.php

It seems that the conditions which Miller and Urey made use of were unrealistic - in as much as they didn't take into account the role of iron and carbonate compounds - which reduce the acidity of water and would cause amino acids to degrade much more slowly. Performing similar experiments in which these compounds are present results in amino acid yields that are hundreds of times greater.

However, Wilkins was still under the impression that the atmosphere would have been non-reducing when it was in all likelihood at least mildly reducing early in the Earth's history - as determined through the analysis of chondrites.

Please see:

Astrobiology Magazine: Reducing Early Earth
Sep 11, 2005
http://www.astrobio.net/news/modules.ph ... e&sid=1708

Outgassing of Ordinary Chondritic Material and Some of its Implications for the Chemistry of Asteroids, Planets, and Satellites
By Laura Schaefer and Bruce Fegley, Jr.
Submitted to Icarus 27 June 2006
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