A Traffic Control System For Molecules

Roland Piquepaille writes "Our cells contain small protein factories which have to deliver materials inside the cell via a network of microtubules. And the transportation is carried out by biomolecular motors. Now, researchers from Delft University of Technology in the Netherlands have built a traffic control system able to force individual molecules to choose between 'roads' by applying strong electrical fields locally at Y-junctions. This traffic control system can potentially lead to new nano-fabrication techniques. Read more for additional references and pictures showing how this traffic system works."

Comments

Right! This won't go wrong

[Quirk]

As anyone who has to make a long commute to and from work knows, we've got traffic control down and running smoothly. Nothing could go wrong here.

interference

[spacerodent]

With the tiny charges they're using would this ever be effective outside the lab setting? I would imagine that the crazy EMF of every day life would seriously fuck these up

Re:interference

[DrSkwid]

How does one measure the presence/absence of an atom compared to the charge of an electron ?

Effecieny is a tin pot dictator.

Troll!

[SEWilco]

Halt, troll molecule!
Get under that bridge!

The Next Step

[Umbral Blot]

All that's missing are tiny traffic cops who hand out tiner speed tickets.

Re:The Next Step

[Anonymous Coward]

Ah, you mean nanotickets.

Minature Train Set!

[sc0p3]

Hottest toy for next Christmas! Train sets so small you can't see them!
Seriously though, as a biomedical engineer, this is bloody scary.

This was the first time that this orientation-dependency of the electrophoretic mobility was observed.

- This occurs in the body, we have microtubles and kinesin in all our cells. The 'research' has shown for *years* that magnetic fields have *no* effect on cancer etc.. so.. it controls Kinesin, but wont affect cells? please.

OK....

[suv4x4]

Ok, so traffic control system for molecules, damn it this means nothing to me... What do I post, what do I post.. Heh a joke always works when you got not clue! I'll ask what the equivalent of traffic cops or talk how "that's the place you don't want a traffic jam to happen". Nah cheesy as hell.

No, wait... I'll voice a concern that's totally unfounded and blow it out of proportions. Nano technology omg, will take over people and turn 'em into zombies! No wait, I'll look more intelligent if it's a question: what if is malfunctions and turn us into zombies? Nah... I've no idea how it works I might come off as a moron.

So what do I say... what do I say. Ah to hell with it!

Microsoft sucks! Hi mom!

Damn it, I think today's not my day... I'll go watch my downloaded episodes of Star Trek and see later.

Re:awesome work

[TapeCutter]

Before we can have "algorithmic control over the mixture and separation of proteins", we need a way to indetify the protiens and tie it to the switching mechanisim. In TFA the researchers used coloured protiens and appear to have switched each "junction" manually. Having said that, it's a neat trick!

OTOH: Early model computers used manually operated telephone switches.

What took so long?

[sbhobdell]

This is all a bit old hat, isn't it?
I was pushing bloodcells around using dielectrophoresis in Uni over a decade ago. Shortly thereafter, water was being tested for purity using the same method, and one of the post-docs was moving tagged proteins around too.
How come it took so long to create a system to be used in protein manufacture?
examples:
http://ieeexplore.ieee.org/xpl/abs_free.jsp?arNumb er=297897 (1994)
http://www.biophysj.org/cgi/content/abstract/77/1/ 516 (1994)
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd= Retrieve&db=PubMed&list_uids=9351287&dopt=Citation (1997)

Re:What took so long?

[pimpimpim]

Well (disclaimer: I did not really read any of the articles), dielectrophoresis seems a 'static' separation technique, to influence position of particles, and this stuff from Cees Dekker seems a sort of dynamic procedure to influence flow of particles, which is a whole step more complex. I would take 10 years to go from one to the other ;)

On a different note, I am a bit dissappointed that it is the same Cees Dekker who is a (or better: the only) big promotor in the Netherlands of the idea of Intelligent Design. This guy is doing such amazing research, that you start to wonder how he could ever combine this with the not very well-founded theory that ID is.

Note to people with mod points: I am stating my personal opinion here: if you disagree, don't mod me down because of this opinion, but give decent replies. If you think the post is crappy for what it is, then mod as you wish.

Maxwell's Demon now a possibility?

[retrosteve]

I always wondered when nanotech would get good enough to find out why (or if) Maxwell's Demon was really impossible.

Now soon we'll know.

Re:Maxwell's Demon now a possibility?

[jamesh]

Doesn't this technology allow a stream of moving molecules to be diverted down one path or another? So the Maxwell's Demon thought experiment would have to be modified so that the molecules would be pumped through a tube where they could be analysed and any that had a temperature above ambient would be diverted into the 'hot' pool, and any that were lower would be diverted back into the 'cold' pool.

Then you have to take into account the pump, the analysis, and the diversion, which would probably cancel out any effect that the 'Demon' would have on the actual temperature of either side, or at least be no more efficient than other methods of pumping heat.

Re:Maxwell's Demon now a possibility?

[wsherman]

Broadly speaking, the Fluctuation Theorem makes it unlikely that you can get more energy out of the sorting than you will have to expend to accomplish the sorting. To put it another way, any sorting process that is not driven by an external energy input will be just as likely to run in reverse. In the classic Maxwell's demon example, a sorting process that can put hot molecules in a specific place will be just as likely to run in reverse and remove hot molecules from that place.

It is interesting to note that the Fluctuation Theorem depends on microscopic reversability (time symmetry of interactions at the atomic level). On the scale that we humans experience things (the macroscopic level), our experience of time is closely correlated with increases in entropy: a person can look at a movie of a drop of ink dissolving in a glass of water and know whether or not the movie is being played in reverse. Essentially, time asymmetry at the macroscopic level (ie. the human scale) depends on time symmetry at the microscopic (atomic) level.

Getting into the realm of very wild and crazy speculation, for classical Newtonian mechanics (charged particles in non-relativistic electric fields), time symmetry holds even when the system experiences external forces (static electric fields). Once we add relativity, however, we get magnetism (magnetism is relativistic contraction of electric fields) and time symmetry does not hold for a system (of charged particles) experiencing an external (static) magnetic field.

To the extent that the Second Law of Thermodynamics still holds in external magnetic fields then it may be possible to prove a version of the Fluctuation Theorem that depends on an even weaker assumption than microscopic reversability. On the other hand, magnetic fields induce spontaneous currents (ordered atomic motion) in diamagnetic materials (superconductors, bismuth, water, etc.) and if it was ever possible to tap into these currents (or any aspect of the ordered atomic motion) then that would show that the Second Law doesn't hold under relativistic conditions (ie. external magnetic fields).

Re:Maxwell's Demon now a possibility?

[Instine]

We're still missing the big one here re Maxwell's demon, which is that we're talking about a closed sytem, which means we need to include the energy gone into creating the Demon. In this case it would include the energy needed to produce human kind, inorder for the boffins to make the system, in order to order the molecules. Or would it? Because that would mean that we'd need to include the creation of the universe. Which means our little tubules have to process a LOT of hot and cold molecules.

Paradox busted I say :)

Re:A Maxwell's Demon idea

[wsherman]

On the subject of tunnels, it's not necessary for the tunnel to involve quantum effects. A simple mechanical tunnel that opened for brief intervals would achieve the same effect: only those atoms with enough speed to traverse the tunnel would be allowed through (effectively only allowing passage to high energy atoms).

However, this mechanical tunnel has the same problem as the quantum tunnel - that the sorting is reversible (high energy atoms/electrons can go in both directions). For the mechanical tunnel, one could imagine putting doors at the ends of the tunnel that would open sequentially which would only allow the high energy atoms to travel in one direction. The problem is that (as explained by the Fluctuation Theorem) eventually the sequence of door openings would reverse and the high energy atoms would be removed from the chamber.

From the point of view of thought experiments, trying to sort atoms by energy gets complicated but simply building a one-way door at the atomic level (allowing atoms to only pass through in one direction) would be sufficient to violate the Second Law of Thermodynamics (eg. the one-way door would cause pressure to build up that could be used to run a motor).

It is trivially easy to build a one-way door on a human scale - for fire safety, doors are required to always let people out but when these doors are locked they don't let people in. The counter-intuitive conclusion of the Fluctuation Theorem, however, is that any atomic level door that can go through a series of steps to let an atom ass in one direction will also go through the reverse steps and allow an atom to pass in the other direction.