Ethics

And Now For Something Completely Different

By Ed Brayton

Let's take a break from litigation and turn our eyes on ligation. The type of ligation I am talking about is connecting two strands of nucleic acids (RNA in this case; a similar process with the same name takes place with amino acids) to make a longer strand. This is an important concept in origins-of-life research (and in biology), because it allows long strands with high information content to be assembled in shorter segments, kind of like a chemical assembly line. (Note that I am using "information content" in the sense of compressibility). In essence this allows Nature to reduce the odds against producing the right sequence of bases in a long strand. It's generally much easier to reliably produce short strands than it is to reliably produce long strands.

Of course, it doesn't do you any good if the shorter strands are simply connecting at random - this doesn't reduce the probability. So what you want is a process that reliably connects the correct strands in the correct order. The process doesn't have to be perfect, just better than random. One way to do this is by speeding up the ligation process for the right strands in the right order - in other words, use a catalyst. RNA has an interesting property - it has a "backbone" that strongly connects linearly, as well as matching base pairs that connect weakly. This means that RNA can act as a catalyst for itself - an autocatalyst. Are there combinations of short RNA strands that reliably catalyze into longer strands?

What would be even cooler is if the longer strand could act as a catalyst that takes the short strands and makes another long strand just like itself. That's self-replication, the first step towards life.

Chemists at the Scripps Research Institute did just that.

Full post as published by Dispatches from the Culture Wars on January 15, 2009 (boomark / email).