Microsoft Word Kurzweil, Ray The Singularity Is Near doc

Emulating Biology. 
The idea of building electronic or mechanical systems that are self-replicating and self-organizing 
is inspired by biology, which relies on these properties. Research published in the 
Proceedings of the National 
Academy of Sciences
described the construction of self-replicating nanowires based on prions, which are self-
replicating proteins. (As detailed in chapter 4, one form of prion appears to play a role in human memory, whereas 
another form is believed to be responsible for variant Creutzfeldt-Iakob disease, the human form of mad-cow 
disease.)
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The team involved in the project used prions as a model because of their natural strength. Because prions do 
not normally conduct electricity, however, the scientists created a genetically modified version containing a thin layer 
of gold, which conducts electricity with low resistance. MIT biology professor Susan Lindquist, who headed the study, 
commented, "Most of the people working on nanocircuits are trying to build them using 'top-down' fabrication 
techniques. We thought we'd try a 'bottom-up' approach, and let molecular self-assembly do the hard work for us." 
The ultimate self-replicating molecule from biology is, of course, DNA. Duke University researchers created 
molecular building blocks called "tiles" out of self-assembling DNA molecules.
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They were able to control the 
structure of the resulting assembly, creating "nanogrids," This technique automatically attaches protein molecules to 
each nanogrid's cell, which could be used to perform computing operations. They also demonstrated a chemical 
process that coated the DNA nanoribbons with silver to create nanowires. Commenting on the article in the September 
26, 2003, issue of the journal Science, lead researcher Hao Yan said, "To use DNA self-assembly to template protein 
molecules or other molecules has been sought for years, and this is the first time it has been demonstrated so clearly."
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