

DNA Logic Gates Calculate a Square Root - jedi_stannis
http://arstechnica.com/science/news/2011/06/dna-logic-gates-calculate-a-square-root-using-130-different-molecules.ars

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ChuckMcM
To my way of thinking I'd like to see a species of grass that factors 2048 bit
integers. Figuring that once a factorization was found it would express a gene
which turned to color of the blade red, then every week after you mow you lawn
you could look through your clippings to find the red ones, sequence those and
then see if you had the keys to any banks. :-)

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wgrover
Nice! If you'd like to write biopunk sci-fi books, I'd read them. :)

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TeMPOraL
I was reading a story by Dukaj - The Cathedral - yesterday, that featured
fields of plants that were doing computations :).

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pjscott
This is DNA strand displacement logic, a particularly simple (yet surprisingly
robust) style of DNA computing. They can chain together "logic gates" made
from reactions of partially complementary DNA oligonucleotides, computing
arbitrary boolean logic functions, in an asynchronous logic style. The big
potential here is that they can use this for drugs (and other biological
purposes) that can do a bit of simple computation. Biology does this sort of
thing all the time -- that's where it gets a lot of its power -- but this kind
of simplified logic is easier for humans.

Looking over the paper, it looks like they figured out how to combine their
seesaw gates and thresholding gates into AND and OR gates, then from there,
used dual-rail asynchronous logic to make a four-bit square root calculator.
They can't make NOT gates (or NAND, or NOR), so each bit gets two "wires",
holding opposite values; this lets them make arbitrary logic without NOT
operations.

There's a pretty slick simulator program you can play with here, along with
more information, if anybody's interested:

<http://research.microsoft.com/en-us/projects/dna/>

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rcthompson
It's neat, but are there any practical applications for this?

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ricree
_Various biomolecules, including DNA, RNA, enzymes, and small molecules, could
all potentially be used as inputs. And it should be possible to link the
outputs into relevant biological functions, including gene expression._

This would suggest, perhaps smart medicines capable of changing their active
makeup based on logic in response to the actual conditions in the body.

Heck, given a lot of advancement it isn't that terribly outlandish to imagine
simple turing complete computers capable of outputting different dna or even
proteins. If that were possible, the benefits should be obvious. Of course,
that's a rather large extrapolation from the limited results in the article.

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rcthompson
But we can already build a small computer with some sensors and medicine
dispensers and implant it like a pacemaker to accomplish more or less the same
thing. However, upon further consideration, I can think of a few areas where
DNA-based logic circuits could plausibly beat silicon-based ones:

* Self-inactivating medicine. For example, insulin that stops working after blood glucose levels return to normal, so that insulin shock does not occur. Also, one could make a medicine that automatically inactivates if its own concentration goes too high, thus preventing overdose. Quicker inactivation can also limit the opportunity for side-effects.

* More precise targeting. One could custom design a medicine such that ot only becomes active at the desired site. For example, an antiviral drug that only activates in areas with high concentrations of virus. Again, this would help limit side-effects.

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gcb
Open publication. nice. take that old, dying, journals.

