X-Message-Number: 21054 Date: Tue, 4 Feb 2003 07:08:09 -0500 From: Thomas Donaldson <> Subject: CryoNet #21045 - #21050 and a bit more for Mr. Kluytmans: In a sense the cost of making these objects is given in Drexler. However I note that we have not made any at all, by your own claim. I would wait to see the results of actually making even one nanodevice: once more, the energy cost cannot be worked out on theoretical grounds alone, unless we have not just a version of the nanodevice created, but a detailed version of the system which creates it. To say that carbon and hydrogen, for instance, would be used to make this nanodevice, is meaningless without a detailed specification of how both elements are obtained and the energy involved in obtaining them. Neither element exists for very long in nature in anything like a pure state. For carbon, for instance, if we're getting it from CO2 then we'd need to calculate the energy involved in gathering together the CO2 and separating the carbon from the oxygen, WITH DEVICES WE EITHER NOW HAVE OR WHICH WE CAN REASONABLY CONSTRUCT. I would say the same, of course, of water as a source of hydrogen and oxygen. The figures I've seen assume that energy has already been spent to produce the raw materials of which we want to build our nanodevices. As for the kind of bonds which hold together biochemical systems, sorry, but you make a BIG error. It may have only been inadvertent, but given that it obviously has affected your thinking about biochemical systems, you should know that individual proteins are bound together much more tightly than by van der Waals forces. Yes, different proteins may be bound less tightly, for good reason. Consider enzymes: they act as nanomachines, and when they hold the molecules on which they're working they MAY hold them lightly. (Even nanodevices would hardly work if they bound to the objects on which they were working too tightly!). This doesn't mean that the enzyme itself is lightly bound together. When a biological molecule is floppy it is so for a reason related to its function: it may have several different forms which can be turned into one another with comparatively small energy. An enzyme may well be more complex than simply a machine to do a single task, specifically to allow other molecules to control how often it does that task and where it does it. Put briefly, a biological molecule isn't just floppy for no reason. It is floppy because that floppiness allows it to perform its function. And if we made our nanodevices rigid, they would also become limited by their rigidity. Indeed, given that your account of Freitas' nanodevice to replace red blood cells, it has several problems of this kind. Sure, it can carry more oxygen, but does that then mean that many of the cells to which it delivers that oxygen must get it not by diffusion over a short distance or actual contact with the red blood cell, but instead by diffusion over a relatively long distance? That hardly sounds very efficient. Again, the walls of our capillaries (and our other blood vessels, too) work because they compress and expand. A rigid object would not move through our circulation as well as a compressible one with movable, extendable walls. Our bones are rigid, but we could not walk without our highly nonrigid muscles... we could not even stand upright. To say that your nanodevices would be more rigid than living systems is a DEFECT, not an advantage. Best wishes and long long life for all, Thomas Donaldson Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=21054