Here’s a neat bit of news. Especially for me as I did my doctoral work studying liquid crystal phase transitions. Scientists have found that snippets of DNA dissolved in water show liquid crystal phases – for reasons that I wouldn’t have guessed. (The snippets are so short that they’re unlikely to have the phases simply because of physical molecular shape:
“Structural analysis of the liquid crystal phases showed that they appeared because such short DNA duplex pairs were able to stick together ‘end-to-end,’ forming rod-shaped aggregates that could then behave like much longer segments of DNA. The sticking was a result of small, oily patches found on the ends of the short DNA segments that help them adhere to each other in a reversible way — much like magnetic buttons — as they expelled water in between them, Clark said.
A key characterization technique employed was X-ray microbeam diffraction combined with in-situ optical microscopy, carried out with researchers from Argonne and Brookhaven National Laboratories. The team using a machine called the Argonne Advanced Photon Source synchrotron that enabled probing of the ‘nano DNA’ molecular organization in single liquid crystal orientation domains only a few microns in size. The experiments provided direct evidence for the columnar stacking of the nano DNA pieces in a fluid liquid crystal phase.
‘The key observation with respect to early life is that this aggregation of nano DNA strands is possible only if they form duplexes,’ Clark said. ‘In a sample of chains in which the bases don’t match and the chains can’t form helical duplexes, we did not observe liquid crystal ordering.’
Subsequent tests by the team involved mixed solutions of complementary and noncomplementary DNA segments, said Clark. The results indicated that essentially all of the complementary DNA bits condensed out in the form of liquid crystal droplets, physically separating them from the noncomplementary DNA segments.
‘We found this to be a remarkable result,’ Clark said. ‘It means that small molecules with the ability to pair up the right way can seek each other out and collect together into drops that are internally self-organized to facilitate the growth of larger pairable molecules.”
Not having read the actual paper, I guessing that what they’ve found is that very small chunks of DNA molecules are exhibiting a nematic phase at reasonable temperatures and concentrations. The big deal here is that such a mechanism would allow for a very efficient method for the snippets of code to organize themselves and bond molecule to molecule to create the longer chains of DNA that we’re all familiar with.
I’m guessing too that the rate of sampling of various configurations would be greatly enhanced by this mechanism, making it much more likely to spontaneous create the self-replicating super molecules like DNA and the proteins that are the basis of life.
There’s a scientist at Lehigh (Behe) that argues for a strong anthropic principle partly on the basis of the structure of a simple protein. Proteins are so complicated that a merely random process of sampling all possible configurations would take much longer than the observed age of the Universe. So, the argument goes, either we got lucky, or God had a hand in this.
But if this study above is verified then at the very least we’d have to redo the calculation of the rate of random sampling – since you wouldn’t have to sample all possible dimensions – just the ones that are available to the aligned molecules.
Read the rest here.