DNA fragments show liquid crystal phase


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.

The Author

Episcopal bishop, dad, astronomer, erstwhile dancer...


  1. >> There’s a scientist at Lehigh (Behe)
    Ha ha… I think there might be some dissent from people who really are scientists. PZ Myers, for one. There’s a wonderful book out called “Evolution”, by Prothero (very readable even for a dog like me!), that is pretty exciting. It’s not at the bio-chemical level, but offers up a wonderful overview of the fossil record which has grown immensely in the last 20 or 25 years. Of course “scientists” like Behe would probably dismiss it as preposterous.

  2. Hi Ozzie. In the years I was at Lehigh I never had a chance to meet Prof. Behe, but I certainly heard a great deal about him. People assumed that I would have a natural affinity for him given my dual fields.
    From what I understand, he’s a competent biologist with a proven ability to do publishable research (he’s got tenure…) But he’s also taken a highly contentious position that is not well supported (I think) by the facts that he’s using to support it.
    As many other people have said (and I have repeated) intelligent design is a nice theological area of study, but until it makes a prediction that can be tested, it’s not science.

  3. John 2007 says

    “but until it makes a prediction that can be tested, it’s not science.” Uh, posted in a rush maybe? Science works with assumptions that cannot be tested all the time, makes predictions that cannot be tested all the time (tho’ I will agree with Popper et all that the best theories state what in fact would falsify a particular theory)and–last–evolution or macroevolution is, of course, a theory that cannot be tested.
    Now, for me, Behe is on to something even if it is not knock down drag out solid. And, for my money, most scientist who pooh-pooh what he says ought to think, or rethink, the connection between function and purpose and, for as much as they challenge theologians, they, the scientists ought to drop the word “selection” which surely implies some kind of “intent”. I would be rich if I had a dime every time some scientist said this or that in the evolutionary process ‘functions’ this way or that or came about ‘in order to’ or for the ‘purpose’ of this or that without realizing how virtually impossible it is to rule out, or carve out, purposive and, therefore, rational order in the universe.
    Maybe just maybe we will all think about the important of the unity of knowledge again and inspire a generation of philosopher-theologians-scientists (maybne through this blog!) and scoot away from the disastrous compartmentalization of knowledge.

  4. Not really a rushed post John, but perhaps more cryptic than helpful. I’m referencing Popper’s ideas that science must be testable if it’s going to be considered science, just as you figured out.
    Speaking as a Christian and as an Anglican priest, I would love to be able to say there was definitive scientific proof of God’s hand in forming creation. Such a proof would follow directly in the words of the psalmist “The Heavens declare”. I’m not a disinterested observer in all this.
    The issue still is that I.D. has yet to predict anything – it’s mostly an attempt to explain an observation. Trust me as a theorist, I was really really good at explaining things. But the only explanation that counted was the one the let me predict something that we hadn’t yet observed. When I did that, I could get published.
    Which is a long way around to say that even if I.D. isn’t science yet, that doesn’t mean there isn’t a scientific basis for thinking about it.
    How’s that? Grin.

  5. >> even if I.D. isn’t science yet?
    Well, the rest of his department there seems, how shall I say this?, skeptical.
    From http://www.lehigh.edu/~inbios/news/evolution.htm
    Department Position on Evolution and “Intelligent Design”
    The faculty in the Department of Biological Sciences is committed to the highest standards of scientific integrity and academic function. This commitment carries with it unwavering support for academic freedom and the free exchange of ideas. It also demands the utmost respect for the scientific method, integrity in the conduct of research, and recognition that the validity of any scientific model comes only as a result of rational hypothesis testing, sound experimentation, and findings that can be replicated by others.
    The department faculty, then, are unequivocal in their support of evolutionary theory, which has its roots in the seminal work of Charles Darwin and has been supported by findings accumulated over 140 years. The sole dissenter from this position, Prof. Michael Behe, is a well-known proponent of “intelligent design.” While we respect Prof. Behe’s right to express his views, they are his alone and are in no way endorsed by the department. It is our collective position that intelligent design has no basis in science, has not been tested experimentally, and should not be regarded as scientific.

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