Biocurious

/ a biophysics blog

A New Kind of Conduction in DNA?

Posted 4 January 2008 by Andre under

My latest Physics World news story discusses some recent work on DNA conduction [free signup required to read the whole article]:

Not long after the double-stranded structure of DNA was revealed by Watson and Crick in 1953, scientists suspected that the molecule might support electrical conduction. This is because the bases in the middle of the double helix stack in a way reminiscent of graphite – which is an excellent conductor. At about the same time, the physicist Leon Brillouin suggested that the DNA backbone, rather than the bases, might support conduction because of its periodic structure.

While the conductive properties of DNA have been studied using a wide range of techniques, most experiments have focused on understanding conduction in terms base stacking and have yielded conflicting results. Alternative or complementary conduction mechanisms – such as Brillouin’s backbone conduction – have been largely ignored.

Now there’s been some new experimental work by Hiromi Ikeura-Sekiguchi and Tetsuhiro Sekiguchi that shows that electrons can in fact delocalize through the backbone of DNA as well:

What they found is that electrons in the backbone delocalize in less than one femtosecond (10-15) in wet DNA. These results imply that electron movement occurs a thousand times faster in the DNA backbone than in the bases stacked in the core.

This work is important because it might help to reconcile some of the seemingly contradictory conduction measurements made so far and it might spark some new ideas on re-engineering DNA to improve its electronic properties but what I found most interesting about this field from my background reading for the story are the potential biological implications of DNA conduction.

One interesting possibility is that enzymes communicate through DNA conduction in order to efficiently find sites of DNA damage that need repairing. This idea has been proposed by Jacqueline Barton, one of the people responsible for a resurgence of interest in DNA conduction in the early 1990s. It has also been proposed that DNA conduction could allow cathodic protection of important segments of DNA by transporting holes injected by oxidants to sites where the damage would have a smaller biological impact. This is one of those ideas that has a nice balance of craziness, potential importance, and plausibility. It might even turn out to be true.

  

  1. Sujit    5 January 08    #

    Nice post.

    Do you have any thoughts on Danny Porath’s group’s recent STM work of DNA? (e.g. http://dx.doi.org/10.1038/nmat2060).


  2. Doug    6 January 08    #

    Were this single stranded RNA, then their likely would be an associated magnetic field.
    I am unsure how double stranded DNA may affect the magnetic fields with electron flows likely in opposite directions.

    The Molecule of the Month: Circadian Clock Proteins posted 1 January 2008 by PhilipJ is composed of amino acids proteins in helical conformation.
    Likely there is also an electron flow in these structures.

    Any helix with an electron flow likely has properties similar to a solenoid.

    See the ‘Iron Core Solenoid’ illustration contrasting an air core with iron core solenoid.
    This GSU HyperPhysics web page has other electromagnetic illustrations.

    http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/elemag.html


  3. alec    8 January 08    #

    Some people also suggested that DNA could work as a semiconductor. A lot yet has to be proved through experiments.


  4. Andre    8 January 08    #

    Sujit,

    Sorry, I don’t really have anything insightful to say about it. What did you think of it?

    Alec,

    That’s true, there have been a lot of seemingly conflicting claims. More experiments will definitely help resolve things (although some aspects of DNA’s electrical properties are pretty well agreed on already I think) but with all of the parameters that are difficult to control in these experiments it’s not clear to me what a killer experiment would look like. More likely, as people identify which parameters are the most important, and what is required to control them, we will see a consensus slowly emerge.

    For those interested in what’s known, Cees Dekker and Mark Ratner wrote a nice review of the state of the art as it stood in 2001. I’m sure things have advanced since then, but it’s still a pretty good read.


  5. A Marques    8 January 08    #

    I’d never thought that the DNA repair cascade might be initiated by a lack or interruption in conduction. It’s actually very much possible…


  6. PhilipJ    8 January 08    #

    I saw a talk by Barton at SFU last year, and it really did seem like a plausible explanation for the way repair enzymes could sense when they were needed. One of the few times in a biology talk that the discussion tended towards wavefunction reflections at site along the backbone of damaged DNA…


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