An example of such life processes is the transmission of information by nerve cells. The cells of the human nervous system are like electric lines that are connected by plugs, called synapses. Up to 1000 signals per second can be transmitted at a synapse, although the mechanism of signal transduction is complicated. Small fat bubbles called vesicles fuse with the outer wall of the cell transmitter and send messenger molecules called neurotransmitters into the cleft between the nerve cells. The neurotransmitters are recognized by the receiver cell. To be ready for the next signal, the sender cell must regenerate the fused vesicles and load them with neurotransmitters. Every such action requires a complex and precise interplay of hundreds of molecules, particularly proteins, that must work together in the correct number and order.
In the pcCell ERC project Frank Noé and his team are looking for answers to the question of how these molecules find each other. The classical idea goes back to Robert Brown, a Scottish botanist of the 18th century who observed that pollen floating on water is in constant random movement. This came to be known as "Brownian motion" or "diffusion." Diffusion requires no special propulsion energy other than heat, and it is a key factor in the microcosm. It allows proteins to constantly keep moving, such that they can find each other and interact. Diffusion is, however, aimless, which raises the issue of whether it is sufficient for the complex coordination of many molecules in the production of neuronal vesicles in such a short time.
The researchers in the ERC project aim to investigate the principle of dynamical sorting. An example of dynamical sorting is as follows: Someone goes to a fair and at the entrance, notices a person who he/she does not know. The chance of meeting this person again after an hour at the fair is very small because that would be a rare event. If a person goes to the fair with a friend, the chance of meeting him/her after an hour at the fair is very large because the two most likely will remain in the vicinity of each other. Where they walk is coordinated, but both can move freely. The principles of movement of the individuals are the same in both cases, whereas the principles of movement of the pair of them are different in the two cases. Such partnerships may also exist between molecules.
Frank Noé and his team are working under the assumption that molecule partnerships are ubiquitous and that they make signal processing in cells sufficiently efficient such that human life and thought is at all possible. It is extremely difficult to demonstrate the existence of molecule partnerships because to do so, several molecules would need to be located simultaneously with very high resolution. Currently, life cell imaging techniques do not offer high enough resolution to achieve that. For that reason the researchers working with Frank Noé in the ERC project are combining computer simulations and novel measurement techniques in order to investigate the proposed molecular partnerships.