An article in the February 2007 Scientific American titled Molecular Lego talks about bis-amino acids and bis-peptides. These are synthetic amino acids and peptide chains formed from them.
The Protein Folding Problem
The biggest problem in programmable matter (true nanotechnology) that cropped up is the continued defiance of nature to reveal to us how proteins will fold. We can specify genes in any sequence we like and harness bacteria to build proteins out of the amino acid sequences we specify, but we have no idea how to predict the 3D shape that natural amino acids will fold into. If we could we could be building nanometer scale machines out of precisely shaped protein components today.
Getting Around the Folding Problem
BIS stands for “two”. Normal amino acids that make up the protein building blocks of life have two arms on them and they connect together into chains by linking an arm on one to an arm on another. They are rather flexible at these arm-to-arm connection points (joints) and the long chains fold at the joints into complex shapes. The forces which govern the folding are subtle and have resisted all efforts to predict. A bis-amino acid is like two normal acids tied together so that each acid has four arms instead of two. Think of two people standing back to back, tied firmly together, with outstretched arms. The two people represent ONE bis-amino acid. When two bis-amino acids join the juncture is rigid. They don’t fold. By engineering a set of bis-amino acid building blocks with the opposing dual-arms at various angles to each other complex and predictable 3D shapes can be built from them – molecular LEGO blocks.
Not There Yet
There are a range of problems with this nascent technology but none appear to be show-stoppers. The basic problems are finding a suitable set of 20 or so stable bis-amino acid building blocks like nature has done then fashion our own assembly line (a bis-ribosome if you will) for them. That doesn’t sound easy but it sounds a whole lot easier than solving the natural protein folding problem.
Further Reading
The principle investigator’s website is Schafmeister Laboratory.