It’s only a matter of time until something very much like life is created in the lab. Until then, scientists are still working on how it happened, nearly 4 billion years ago. The research is promising.
With the aid of a straightforward experiment, researchers have provided some clues to one of biology’s most complex questions: how ancient organic molecules came together to form the basis of life.
Specifically, this study demonstrated how ancient RNA joined together to reach a biologically relevant length.
RNA, the single-stranded precursor to DNA, normally expands one nucleic base at a time, growing sequentially like a linked chain. The problem is that in the primordial world RNA molecules didn’t have enzymes to catalyze this reaction, and while RNA growth can proceed naturally, the rate would be so slow the RNA could never get more than a few pieces long (for as nucleic bases attach to one end, they can also drop off the other).
Ernesto Di Mauro and colleagues examined if there was some mechanism to overcome this thermodynamic barrier, by incubating short RNA fragments in water of different temperatures and pH.
They found that under favorable conditions (acidic environment and temperature lower than 70 degrees Celsius), pieces ranging from 10-24 in length could naturally fuse into larger fragments, generally within 14 hours.
The RNA fragments came together as double-stranded structures then joined at the ends. The fragments did not have to be the same size, but the efficiency of the reactions was dependent on fragment size (larger is better, though efficiency drops again after reaching around 100) and the similarity of the fragment sequences.
The researchers note that this spontaneous fusing, or ligation, would [be] a simple way for RNA to overcome initial barriers to growth and reach a biologically important size; at around 100 bases long, RNA molecules can begin to fold into functional, 3D shapes.
Enzymes basically make things go faster. That means that reactions that are caused by a particular protein (say, lactase breaking down lactose into its constituents – if you can’t do this or do it poorly, you’re lactose intolerant) can happen anyway, but they will happen far more slowly. In some instances, they essentially will not happen except by tremendous stroke of luck (though, again, the potential is always there).
What’s particularly interesting to note here is that it is very difficult to say what the pH balance of different bodies of water would be on an early Earth. It is entirely plausible that acidic levels would be higher, leading to the ability of these RNA molecules to form 3D shapes. And, of course, because biology is very much dependent on shape, these formations could act as proteins, if not plainly be defined as such. By doing this, a rudimentary evolution could begin to take place. We may not define these replicators as being life, but they would hold many of its characteristics – taking in energy and out, being subject to at least a form of natural selection.
Filed under: Evolution | Tagged: Active configuration, DNA, Early life, enzymes, Ernesto Di Mauro, Fabiana Ciciriello, Giovanna Costanzo, Ligation, Nonenzymatic RNA ligation in water, precursor, proteins, RNA, RNA world, Samanta Pino, sciencedaily.net, single-stranded | Leave a comment »
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