Researchers Build Logic Gates With RNA 58
Ars Technica reports on research out of Cal Tech where scientists were able to create logic gates out of RNA molecules. Thus far, they've demonstrated AND gates and OR gates, with work proceeding on more complicated systems. The work shows promise for ability to easily detect the presence of particular chemicals. The abstract from the scientists' paper is available at Science. Quoting Ars:
"Detecting tetracycline isn't especially interesting, but RNA that binds to specific small molecules is actually relatively easy to make; repeated rounds of amplification and selection for binding can evolve these RNAs in a couple of days. This means that, in a matter of days, researchers can grow yeast colonies that glow in response to a variety of chemicals, or even to combinations of chemicals. More complicated circuits should be possible if the ribozymes are inserted into messenger RNAs that encode transcription factors, which could, in turn, regulate genes that encode yet other ribozymes."
I don't know if they need a cell (Score:5, Interesting)
1. Actually, I don't know if they really need a cell.
Even from the viewpoint of life evolution on Earth, it all started with some self-replicating ribosyme that "lived" perfectly well in the soup of aminoacids and nucleotides around it. The cell was just an increasingly complex test tube around that reaction, complete with increasingly complex ways of regulating the exact composition of the contained drop of sea water.
I can see how that was an advantage to evolve, in a primordial soup that was hit and miss anyway and probably (very slowly) degrading in quality over time. But in a lab, we can do that regulating artifficially. Admittedly, using a cell might be cheaper, but we can do without it too.
And indeed there is plenty of organic stuff we already do without a cell. E.g., detecting certain DNA sequences is done via enzymes which bind exactly to one sequence, and start replicating it until it's enough to be detected. We don't really build specialized cells for that.
2. Actually, to me another aspect is more interesting there: the fact that it's all done with RNA.
Proteins already _do_ exactly what these guys seem to do: bind only to certain mollecule configurations, but not to others. You can see it as logic operations and whatnot, but really it's all chemistry and that's all it does: bind only to certain mollecules, but not to others. It's a bit like saying that a keyring with two keys is a mechanical OR gate: it unlocks a lock that matches either key 1 or key 2. It's simultaneously technically true, and a bit misleading.
But there's a more interesting aspect to it: your body usually uses proteins for that, and DNA/RNA is just a way to encode a protein which will actually do the matching. E.g., those enzymes I mentioned, are proteins. They do all the heavy duty chemistry, from processing the cell's "food", to regulating what goes in or out, to destroying all chemicals which are non-polar and pass right through the cell wall instead of being regulated by the protein valves on the wall, to movement, to DNA repairs, to regulating what other proteins are built and where do they go.
As long as that's all the model we know, that needs a rather complex initial configuration for the start of life. You need something that's capable not only of replicating itself, but also of encoding proteins. It's already a bit too big an incredible machine, and appearing out of nowhere, even after billions of years and trillions of tries per second, still is a damn improbable event.
But that everything can be done via RNA only, that opens a whole new possibility. We already know that RNA can replicate itself. If it can also take the functions of a protein, offers a much simpler initial configuration for life. It's entirely possible that assembling proteins came later, as a better replacement, much like DNA later replaced RNA as the encoding of choice. The first cells could have been RNA-only, but could still have a metabolism and be able to regulate themselves well enough.
I find that fascinating.
Great for homebrewers! (Score:3, Interesting)
As a homebrewer, there are lots of chemicals that show up in beer, some good, some bad. It would be great to modify a strain of yeast that would glow when diacetyl or some other chemical was present.