[jrl]

Enzymes can add hydroxyl groups to molecules in specific locations. A hydroxyl group contains only two atoms. Enzymes can also remove a couple of hydrogen atoms and their electrons in particular places of a molecule. By combining these and similar reactions, cells can do extremely specific remodeling of compounds. For example, a single bond in a fatty acid chain can be turned into a double bond by the dehydrogenation reaction mentioned before, and then hydration and subsequent oxidation yields a keto group. The overall change represent the addition of ONE oxygen to the molecule in the same position.

This means that beta oxidation (the metabolic pathway where those reactions take place) of fatty acids involve manipulation of molecules at the atomic level. Drexler describes a path from biochemistry to molecular manufacturing in Engines of Creation. In fact, part of his argument is that biochemistry is similar to a great extent to the molecular machines he envisions.

[maaku]

This is not atomically precise, mechanosynthetic manufacturing. Can you use such a construction to create carbon nanotubes or equivalent and then lay them out in a three dimensional lattice structure with nanometer precision and six-sigma workpiece reliability?

Biology does not scale to Drexlarian nanotech. The domains are completely different.

[jrl]

"Can you use such a construction to create carbon nanotubes or equivalent and then lay them out in a three dimensional lattice structure with nanometer precision and six-sigma workpiece reliability?"

I can use biochemistry to build second-generation machines which might be capable of doing that. We might not have a diamondoid nanomachine but we can eventually synthesize it, since biology gives us atomically precise positioning of atoms. This looks like a feasible way to develop Drexlerian nanotech.

An analogy with computer programming could be that biology is like assembly language. Using that you can make a higher-level language such as C, and from there you can develop much more powerful abstractions and technologies (Python, Perl, Lisp, Ruby, etc.)

The domains of biochemistry and molecular manufacturing are not completely different because the former could be the foundation of the latter. Also, the science behind biology can inform nanotech. Transforming mechanical energy into chemical processes and viceversa are common processes in cells (e.g., motor proteins.), this is very similar to the type of processes molecular nanotech aspires to make.

Another thing is that cells are capable of correcting errors in DNA synthesis to a substantial degree, 1 mistake for every 1 to 10 billion nucleotides. Reliability isn't an insurmountable problem in biology.

"This is not atomically precise, mechanosynthetic manufacturing."

But we can agree that biology can do atomically precise synthesis. And enzymatic catalysis can sometimes be described in terms of mechanical bending of molecules, such as the ATP synthase.

If biochemistry were so irrelevant to molecular manufacturing, Drexler wouldn't have written so many pages talking about it or suggesting it as way to develop nanotech.

[jrkelly]

Why can't you use biology to do what you want there? Proteins have ~0.05nm precision at placing atoms and are programmable in three dimensions and biology is pretty good at working with carbon. It exceeds our genetic engineering ability today, but we're getting better. Semiconductor Research Corp recently put some money towards this: http://www.src.org/newsroom/press-release/2013/521/