Processing with peptides

Networks of peptides can mimic logic gates.

As silicon chips increasingly come up against the laws of physics, researchers are looking around for the technology that will power the next generation of computers. As well as exploring the possibility of developing computers that work with light or subatomic particles, some researchers are turning to biology.

Nucleic acids, proteins and living cells have all been engineered to perform simple computing functions, but now a team of chemists and molecular biologists from the Scripps Research Institute, La Jolla, California, US, has shown that such functions can be performed by even simpler biological compounds. The researchers have developed networks of peptides that can mimic the actions of the simple logic gates that form the building blocks of all computing.

The idea is to group together a series of peptides that catalyse the formation of either other peptides or copies of themselves by joining together precursor peptides. These template peptides, together with the precursors, act as the input with the combined peptides as the output. The researchers created networks of these template peptides, which they had developed as part of previous research, that were able to act as OR, NOT, NOR and NOTIF logic gates.

An OR gate involves two inputs and an output, with the output only generated in the presence of either or both inputs. To create such a gate, the researchers developed networks based on three peptides, in which two of the peptides catalysed the formation of the third. Only if either or both of the two catalysing peptides were present in the network would the third peptide be produced.

As well as generating outputs, peptide networks can also block them, as a result of different template peptides competing for the same precursor peptide. For instance, the researchers were able to create a NOR gate, which is the opposite of an OR gate, by using a network of three peptides in which one of the peptides catalysed the formation of itself. However, if linked to either of two peptides that used the same precursor peptide more efficiently, the output of the self-catalysing peptide was greatly reduced.

The researchers argue that their fairly simple peptide system will help scientists understand the computing ability of more complex cellular networks.

Jon Evans