5 Responses to “Molecular motor fueled by ATP made at Cornell”

1. kurt2100 Says:
   November 26th, 2000 at 11:59 PM

   About time

   Its about time.

2. MarkGubrud Says:
   November 27th, 2000 at 1:43 PM

   What, me worry?

   By now, the front-end writers for Science know just how to calibrate the correct balance of honesty and sarcasm in discussing the idea of assembler-based nanotechnology. Here Robert Service has enlisted Richard Smalley to do the dirty work:

   Richard Smalley, a Nobel Prize-winning chemist at Rice University in Houston, Texas, says that there are several good reasons to believe that nanomachines of the sort imagined by Drexler and company can never be made. "To put it bluntly, I think it's impossible," Smalley says.

   Well, Smalley sat on a panel with Ralph Merkle in a Congressional hearing in June of last year, and said nothing about MNT being "impossible".

   As he sees it, the idea of little machines that grab atoms and assemble them into desired arrangements suffers from three faults. First, he says, it's wrong to think you can just manipulate an individual atom without handling the ones around it as well.

   Never mind that no serious MNT theorist pretends that you could.

   "The essence of chemistry is missing here. Chemistry is not just sticking one atom in one place and then going and grabbing another. Chemistry is the concerted motion of at least 10 atoms."

   I suppose this explains why no diatomic molecules exist.

   That means to move that one atom where you want it, you'll need 10 nanosized appendages to handle it along with all of its neighbors.

   Of course any design for an assembler system will have to take account of the motions of atoms in the vicinity of the reacting unit (which need not, and in many cases probably would not, be a single atom, but a group, possibly even a rather large molecular unit). But this does not imply that the reaction dynamics will be impossibly complicated to predict and control. Most of the motion will be confined to one or a few degrees of freedom involving only a few atoms. The motions of surrounding atoms need not always be completely controlled, but only constrained within certain limits.

   Which raises the second problem–what Smalley calls the "fat fingers" problem. A nanometer is just the width of eight oxygen atoms. So even if you're trying to build something hundreds of nanometers in size, "there's just not enough room" in that space to fit those 10 fingers along with everything they are trying to manipulate.

   First of all, "fingers" is a naive and incorrect image. Of course you don't have little fingers just picking up atoms and placing them one at a time. What you have is an assembler arm which determines position, angle, and applied forces, torques, voltages, etc. The end of the arm is a binding site which binds reversibly to a variety of "tool molecules" which carry the units to be added to the workpiece-in-progress. When the reaction is completed, and the unit has been transferred from the tool to the workpiece, the remainder of the tool is docked in its proper recycling station and unbound from the arm.

   Of course the girth and extent of the arm will constrain the types of structures that can be assembled. Many chemically stable structures may prove inaccessible by direct assembly, but other tricks involving "robotic" actuators as well as self-assembly and traditional chemical synthesis pathways may make some such structures accessible as subunits to be assembled into larger systems. The fact that not all structures may be directly accessible does not prove that assemblers cannot "close the loop" of self-replication and serve as the basis for a versatile manufacturing system.

   Finally, there's the "sticky fingers" problem: Even if you could wedge all those little claspers in there with their atomic cargo, you'd have to get them to release those atoms on command.

   Again, it's the wrong image. Anyway, we do know how to reversibly bind and unbind. STM experiments have already demonstrated that this can be done repeatedly in reactions with single atoms. Again, this is a cheap shot, lazy and dishonest. But I wonder if Richard Smalley still makes these arguments, or if Service was only quoting some statements he may have made several years ago.

   "My advice is, don't worry about self-replicating nanobots," says Smalley. "It's not real now and will never be in the future."

   What, me worry?

3. Saturngraphix Says:
   November 30th, 2000 at 5:46 AM

   Re:What, me worry?

   Few possibilities of what might be going on in Richards mind:

   1) He is falling prey to what commonly happens to scientist working too focused in a field…he lacks the ability to contemplate what can be done in 10 years because he can only see what can be done in 1.

   2) These quotes are old and outdated from him and he doesn't want to be proven wrong while he is alive (when your dead, who cares if your wrong). He may change his mind if he is cured of his cancer though…living means sometimes eating your words (I think he would secretly love to eat his words about this).

   3) He is securing money for the field by making sure not to sound like a quack so early on talking about nanobots and unlimited resources…tends to sound like snake oil if right after you want to ask for grants. In this case, he is doing a saints job…telling what we can accomplish and market in a couple years is the best way to have someone loan you money…talking about being immortal and godlike may get you a "will play with your atomic structure for food" sign and a cozy corner on a semi-busy highway.

   Smalley is not in assembler business…he is nanocommercialism and a good frontrunner of what Nanotech is presently. He is also doing alot for the cause…so just because he is not talking about nanites and the wonders to come, doesn't mean he isn't drumming up heavy professional interest in the rest of the field. Whatever his motives are, they are valid right now and that is important in securing spin-off tech to get funded. I say cheers to the attention he has brought…not from SF fans (dime a dozen) but from commercial and government R&D crews
   (however, I would think perhaps if he left a bit more mystery to his comments rather than flat out stating it wont work might at this point be in his best interest, especially since a basic nanomedbot is being tested out as we speak…err…type).

   Saturn

4. kurt2100 Says:
   November 30th, 2000 at 6:18 PM

   Re:What, me worry?

   Given our discussions on the advantages of biotech over nanotech, I'm supprised at your posting here. I actually am still unconvinced that "drexlerian" assembler-based nanotech is possible (although I am less skeptical than I was 10 years ago). I do admit to the possiblility of "mechano-chemistry", since this is how dynamite combusts and some of the cell membranes contain molecular "revolving-doors" that pass chemicals through the cell-mebrane. My main objection to "assembly-based" nanotech is that such a "general-purpose" assembler requires the ability to chemically identify atoms and to combine them arbitrarly with other atoms. As of yet, I am unconvinced that this is possible, espcially with the entire apparatus (assembler) being of the size that Drexler proposes. Different reaction mechanisms create different products. That's the reason why nature doesn't do it that way. Instead, nature controls reaction-site specifivity by means of protein folding, diffusion-driven processes based on reactant concentrations, and some mechano-chemistry.

   Some of Richard Smalley's arguments are redherrings. But I have yet to see any progress in overcoming any of the aformentioned technical barriers to suggest that such a "general-purpose" chemistry is possible.

5. kurt2100 Says:
   November 30th, 2000 at 7:02 PM

   the advantages of solution-phase chemistry

   For purpose of discussion: Dry¡¨ nanotech = Drexlerian nanotech, which is based on ¡§mechano-chemistry which is presumed to take place in a vacuum environment.¡§Wet¡¨ nanotech = ¡§biological¡¨-like nanotech, which is based on solution-phase chemistry

   The advantages of ¡§wet¡¦ nanotech over ¡§dry¡¨ nanotech:

   1) Solution-phase chemistry offers many more possibilities for materials manufacturing than ¡§dry¡¨ nanotech
   2) A greater variety of reaction pathways available
   3) Will be cheaper for many fabrication applications because less ¡§engineering¡¨ of the assembly process is required
   4) More possibilities based on use of different solvents, the role of solvent in chemistry still not completely understood, but is very powerful. For example, it requires a temperature of 1500C to disassociate table salt, NaCl, but water solvent does it at room temperature.
   5) 90% of the reported developments occurring in nanotech involve solution-phase chemistry.

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