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Science

DNA Strands as Semiconductors 42

Posted by Hemos from the conjunction-junction dept.
Dyslexic writes "ABCNews is reporting that strands of DNA can act like semiconductors. After seeing "The Matrix" this makes me only fear the future." The research is coming from two researchers in Basel, Switzerland. Essentially, this research is saying that while DNA makes a good semiconductor, it does not conduct as well as, say, copper. It's real usefulness comes from the fact that "...he knows of no metallic wires that can be made as small or as regular as DNA strands. A strand is 2 billionths of a meter thick, or one-forty-four-thousandths of the diameter of a medium-size human hair ". Uber-thin. I like it.
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DNA Strands as Semiconductors More

DNA Strands as Semiconductors

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  • Wauw (Score:1)

    by gavinhall ( 33 )
    Posted by JoeyRamone:

    Yes boys and girls the star-trek future comes closer and closer :), I'm happy. This is exiting, only hope Intel doesn't run of with it or, heaven forbid, kills the technology, just like the car-industry is doing with hydro-propulsed (is that right?) cars.
  • Posted by F.A.N.G.:

    I see nothing describing DNA chains as semiconductors, only as poor conductors.
    For the love of mike, please tell me you know the difference.
  • Posted by jclanfear:

    It is crap. I can't remember what it actually referred to, but it wasn't general brain function.
    (It's also several decades old, so I wouldn't bet on it being correct for anything.)

    (Neurons that aren't utilized tend to die as part of the brain's optimizations. AFAIK I'm not missing 90% of my brain (of course I don't check it all that often).)
  • Seems that this subject comes up about every six months here on SlashDot. Interesting spin with the DNA this time. I will have to dig a little bit to respond with a 100% confidance factor, but I will tell you right now, I doubt some of this.

    I have looked very deeply into the field of "molecular wires" and found several flaws. The published journal articals on this that I know of all use a high level of congugated pi bond interaction as the mechinism for the transport of electrons. Although this produces a remarkable increase in electrical conductivity compared to a "normal" molecule, the ability to conduct electrical current still drops off exponentially as a function of distance. Or, in other words, unless the whole circut is only a few ~30 atoms long, it would require enough juice to totally distroy it to get any electrical flow across it!

    Now, there is the possability of "bundleing" these systems, maybe using something such as carbon nanotubes (maybe several of them built one on top of each other) to overcome this, but the fabrication process for doing something like this is more science fiction right now than science. Maybe that's what they are trying with the DNA stuff, but from what I know, it's not possable.

    But, AGAIN, I point to a possability that is realistic. If you look at some of the work done in IBM labs, specifically The Almaden Lab [ibm.com] and the one in Zurich (don't have the URL on hand, but there is one), you can see something that would be superior on TWO counts. Actually using indivual atoms insted of full molecules. Positioning highly conductive METAL atoms (not carbon molecules) on a semiconductor surface (carbon), it might be possable to create a circut that would stand a much higher chance of working, AND be much smaller. Right now, I believe that IBM is using this technology to try to work towards data storage at an atomic level, which, in theory, could fit the Library of Congress on a postage stamp. ;-) But even this work is limited, AFAIK, to very low temperature (like 10K?) and is not truely practical.

    But, this shows more hope, as I have seen a few research groups position molecules (buckyball) with STM on a surface at almost room temprature. To me, at least, this is much more realistic, and much much more exciting research.

  • You actually might just need something like an AFM, if you could get things in the right environment. Zone Electrophoresis (spelling?) to denaturalize the strand and line up the groups as you could predict, then just AFM (Atomic Force Microscope) them... ? K, off the wall idea, maybe not, it's not my field. Sorry.

    The potential to rapidly get the sequence of a DNA strand is a very hot field, and very heavily government funded. Based primarily in the Human Genome (spelling?) Project, I believe. So, I don't doubt there is a lot of work on rapidly "reading" DNA.

    But, this begs the question, how are you going to accurately build long strands of DNA, sequenced exactly as you would like them to be, in order to store data on them? And, why DNA? Potentially, you could use something easier to detect (cool tagged or marked base pairs if DNA, or something totally diffrent), and easier to build?

  • Of course, that's where it gets fun to think about and read about. The potential for structuring switches... etc...

    Not a limitation, but a new field of investigation. Classically, electronics is something that has been looked at very one dimentionally. Consider the switch set to off, and not only are you stoping flow in a liniar direction and influancing one data point, your have a flow of electrons tunneling into bulk, and influancing the behaviour of the whole circut.

    Yes, it's not a classical model. But, I don't believe it's an unusable consept. Gates and switches have a much wider base from which to be developed. And, the actual movement of an atom from the tip of an STM is one of the first examples of something with known physical mass actually tunneling! Wahoo... think, this is not as we know it, this is new, and of course it's not classical, by any sence, but, that also means it's not subject to classical limitations.

  • matrix (Score:1)

    by mattdm ( 1931 )
    Why should this make you fear the future? The Matrix was an interesting illustration of extreme mind-body dualism, with neat-o special effects. But it's technologically implausible, and especially has nothing to do with this. It's just saying that DNA is good material to build small wires from. It has nothing to do with what would be needed to build the matrix from the movie -- that's about extremely complicated (yet ultimately stupid -- hello, nuclear power) artificial intelligence combined with a complete understanding of the mind/body interconnects (even though it's likely actually impossible to seperate the two).

    So I wouldn't worry.

    --

  • Where does this number come from? One hears it all the time, but it sounds like crap to me.

    --

  • Umm .. you already have a computer in your brain.
  • otherwise known as "bucky tubes" make better wires, etc...

    I'm working on rod logic computers right now, actually, in between all my other classes. (yay 20-unit load!) designing a computer from the groun up has never been so much fun!

    check out ralph merkle's stuff too... he's got GREAT stuff, and is absolutely dominating the field. bistable logic, anyone?

    www.merkle.com

    Lea
  • You could fairly easily identify a *very* short sequence, say 4-10 base pairs by NMR spectroscopy. Longer sequences require far too much effort, and would likely have to rely on multi-dimensional NMR. The biochemical method of sequencing (using gel assays, etc.) is far superior and faster, which is why scientists use it. :)

    Microscopy for sequencing is out of the question I think. Way too involved, expensive, and time consuming. The only way I can see that a DNA wire could be useful is if you could grow them in situ on some kind of support. DNA is a fairly fragile biomolecule and you can't deposit it in any way even resembling solid state techniques.
  • The problem with atomic scale systems is that you will run into quantum mechanical effects. While this may be desirable in quantum computing systems, it is NOT desirable in the classical regime.
  • now someday I can have a computer in my brain, can't wait...

    This should be called "microsoft" like the guy who wrote Neuromancer called it.
  • Wow...think of the Beowulf Cluster I could make with my body...

    (sorry)
  • at those scales nano-mechanic movement actually could be fast enough (I think) to overtake electrical impulses (unless they'd be travelling in a perfect superconductor).
    Actually this isn't true. Even at the nanometer scale, mechanical disturbances (motions of atomic nuclei) move at the speed of sound, while photons and electrons move at or near the speed of light. Bonded atomic nuclei are like masses connected by springs, and the square root of the ratio of spring constant to mass (times some physical constants) gives you the speed of sound.

    Electronic and photonic systems will always be faster than mechanical systems, but initially, mechanical systems may be easier to get working.

  • I wonder if the strands could be "read" by electrical means.?. After all, DNA is ultimately a biologically evolved four-state memory device.

    One method: If each base has a unique resonant frequency (or set of frequencies, like little tiny antennas - akin to spectroscopy), and you "modulate" a strand at each resonance set, would you be able to extract an RF profile or "image" of the strand's sequence? Scanning Capacitance Microscopes [www.bell-labs.com] might do the trick.

    Just a thought...
  • The complementary nature of the bases should actually work in your favour. My proposal/idea does depend on uniquely identifiable RF signatures for each base, relative to the other three. If this is the case, you apply each signature in sequence and watch/scan for the resonance. The existance of one pair over the other would strengthen that pair of RF signatures; orientation would show up via the scanning action, maybe some phase variation/difference.

    I would expect the hydrogen bonding interference to be relatively easy to filter out; treat it as (average) background noise and filter with a little signal processing. You would have four sets of data (one per base) to work with, making it that much easier. Apply some sort of "helix transform" to account for differences in base-pair oriention from one to the next...

    I guess we'll just have to wait and see! :-)

    (caveat: my background is in electrical engineering, semiconductors and mathematics, not biology and chemistry, so apply holes in my logic as you see fit.)
  • Would resonance be affected? Most likely. Like an antenna, I would expect a base-pair (v.s. individual bases) to be "de-tuned" by their close/attached proximity. A difference in behaviour should manifest itself as some sort of "polar" RF signature for the pair.

    Analogy time:

    Think of it as a magnet with four possible orientations. You're looking at the difference between N-S, W-E, E-W and S-N orientations with an unmarked (no N/S/E/W markings) compass. You can determine the orientation of one magnet relative to another by watching and recording the relative changes on the compass when you bring it near each. Compare that to a set of known samples, and the actual orientations fall out of the measurements.

    eg. You measure: abd-cdd-aba. You then bring calibrate your compass with some known samples and discover that a=NS, b=EW, c=SN, d=WE. From your measurements, you get: (NS)(EW)(WE)-(SN)(WE)(WE)-(NS)(EW)(NS)

    Grossly over-simplified, but hopefully a little more clear. :-) If the two types of base-pairs have "sufficiently different" signatures, the task is easier because it's like being able to automatically distinguish between a N-S/S-N magnet and a W-E/E-W magnet by their shape.

    eg. You already know that (a,c) forms a pair of measurements and (b,d) forms another pair. Calibrate to differentiate between a and c, and between b and d.

    Plenty of research potential, eh?

  • Ouch! (Score:1)

    by Stalke ( 20083 )
    Not to mention what happens when you put too much current through a strand of dna. Personally, I wouldn't want to fry my dna. Next thing that will happen is that I'll start to grow a microsoft symbol on my forehead.
  • Wouldn't it be much better to concentrate on getting mechanical nano-computers to work on this kind of scale rather than building smaller electric ones? (Please read K. Eric Drexler's "Engines Of Creation" [foresight.org].) Strikes me that's the more worthwhile avenue of research, especially since we'll be hitting more and more problems with electron tunnelling and at those scales nano-mechanic movement actually could be fast enough (I think) to overtake electrical impulses (unless they'd be travelling in a perfect superconductor).

    Never mind all the other goodies we could get with nano-machines! ;]


    Herbert von Kammerstein

  • If DNA strands work for semi-conductors make me into a cyborg!!!
  • I think there is an inherent fear that comes with mixing technology and our body. Even though the matrix was not exactly related to using DNA as a semi-conductor, it was a movie that showed us a possiable end scenario of man vs. machine. I believe this is what the author of the post meant when he said he fears the future of this.

    I personally would be scared of integrated technology with my brain. It gives viruses a whole new meaning. Although the thought of having computing power inside your mind is fascinating, I still think it is way far off from what you and I would consider cool.

    ~pearcec
  • Mechanical computers are one of the worst nanotech ideas. They are a "proof of concept" thing to demonstrate that nano-scale computers are possible, because in absence of experiment it is easier to convince people that bumpy nanosticks can compute than that the quantum effects can be dealt with. Drexler needed something possible to point at, I doubt even he seriously thinks mechanical computers are the way of the future.

    They are definitely way slower than an equivalent-scaled electronic or light-based design. They are indeed theoretically a bit faster (about 1 GHz and 1000 MIPS) than your current average production chip (when "Engines of Creation" came out, the gap was much wider), but it is a theoretical high estimate which conventional electronic designs have already overtaken.

    Realistically, do you think it's more efficient to move around hundreds of whole atoms or a few electrons or photons? (the concept of single-particle signalling is a very exciting one to me)

    Incidentally, I have a copy of Nanosystems on my lap as I type this. I've read it, but I don't have the expertise to check his work. It is very thorough and quite interesting if you like theoretical engineering.
  • Gotta agree with you on the internal computer bit; I would be hestitant about it... early adopter does not have my name on it. Instead, why not try to find the means to unlock and use that substantial amount that is already there. I mean, if we can do the activities and such that all of us do, and only use 10-15% of the brain, imagine the computational capacity if just 50% was used. Or even higher... Then, we might scoff at internal computers, knowing that it was a foolish I idea for the lazy, but then, I ramble...
  • I think it would be neat if we could develop a game/simulator that allows you interact with basic elements found in nature such as rocks, dirt, trees, etc on a physical level. To build a house you would first have to put together the tools you need. Everything would rely on what you wanted to do and what you could figure out how to do with the basic elements. It would be the ultimate civilization game.

    It would be very impratical and hard to program because you need to model the world to a great level of detail. It also wouldn't sell to well to today's action/WWF obsessed gamers, but if done right it would be totally immersive, and I would have fun playing it.
  • That may be all well and true.

    Although we do have computers in our brains, in the form of our brains, the problem with human thought is that it's not quite 'linear' or 'computatational'.

    Human beings lend themselves well to solving 'fuzzy' problems, but stuff like 2+2 and matrix muls eats time. Most of us have to count it out in our heads in some way.

    Now if we could reverse engineer our brains and engineer in our own ALUs to our own cortexes, that would be very handy. I could delegate computational processing to that computer-like part of my brain, and leave the rest of my brain and consciousness free to deal with the more pressing fuzzy problems human beings are so good at - like abstraction, problem solving, decision making and model building.

    What I'm saying is that if we harness this innovation, and use it for the good of humanity, all well and good. It could equally be used to control people. Usual hacker disclaimers/restrictions apply, but from a hacker p.o.v, I like the idea of having more control over my own brain. If I could engineer new computational functionality into it, leaving the rest of my brain free to do the important things, that would be great.

    See the difference between 'arithmetic' and 'mathematics'. One isn't really a subset of the other. Arithmetic is what computers do. Mathematics explains why and how they do it.
  • I know that thermal runaway at the molecular level could ruin your day (Can you say spontaneous combustion). Better to make Organic machines than to incorporate an inherently unstable electromagnetic field into your own body.
  • DNA denatures above 40 C. Moreover,
    300 MHz will frie the molecule
    beyond recognition...
  • A few people are making devices to attempt to do faster, mass sequencing. Lydia Sohn's group at Princeton has assembled two-probe platinum devices which, at the present, only detect a change in capacitance when the DNA strand spans the gap b/w probes. Obviously this is pretty far from being able to sequence anything. The thing people forget about though is that human DNA is pretty huge (>~30 microns in length) and has been scanned succesfully by atomic force microscopy (AFM) in solution at room temperature (e.g. work by Lindsay's group at ASU >5 yrs ago). The big stumbling block in sequencing using electronic transport is an extremely sketchy knowledge of the electronic states one should expect as well as the inherent thermal (Johnson/Nyquist)noise at the temperature range that would not destroy the molecule.

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