How a cell is like an opera house
While talking casually to somebody about my research into noise in life science I began to realise we were talking at cross purposes: they were thinking about noise in the most common sense of the word, the sound that things make. Audible ‘noise’ in everyday language is detected by sensing vibrations in the air using our sensitive ear drums or even by sensing loud vibrations in surfaces. This is what Beethoven did when he cut the legs off his piano to feel it resonating though the floor, frustrated by his increasing deafness.
But noise in a technical sense isn’t necessarily the same as sound, Beethoven’s piano was generating a signal, the frequencies of vibrations propagating from particle to particle in the wooden floor were precise and intended. When a piano key is pressed a hammer strikes a taut string, causing it vibrate up and down at a specific frequency which differs between musical notes. This vibrates the air around it, which is how Beethoven in his younger days would have received this musical signal. It also vibrates the wooden piano itself, the floor it rests on eventually spreading through the solid surfaces of the room and building – how Beethoven would sense the signal after his deafness. As this musical signal travels from the source, the piano, to the receiver, Beethoven, we can expect there to be some contamination, amplification, or dampening to the pure signal as it travels through the room. In other words noise will be introduced to the signal – any deviation from the generated signal before it is detected by the listener can be thought of as noise. Anybody who is familiar in principle with the idea of tuning a radio can appreciate this concept.
Noise has long been a source of agony for physicists and engineers who deal with acoustics – performance venues have lived and died on their treatment of noise. The architecture of the Sydney opera house is famously celebrated, however there are plenty of articles grumbling about the poor acoustics of the building. This is because the size and shape of the rooms is such that it causes the musical signal generated by the players on stage to bounce off the walls and collide like separate waves in a puddle – creating pockets of turbulence, artificial loudness and quietness. The nature of music is that it has to be played somewhere, in a concert hall, a train station, played somewhat too close for comfort on the patio of a restaurant by three men with bold moustaches, noise will always be a factor in acoustic signals.
Imagine how crystalline and clear Beethoven’s piano would sound if the player and instrument were somehow suspended in mid-air, in a completely isolated pocket of the universe with no walls, no trees or annoyed looking waiters. It would sound very alien, neglecting the noise of the signal bouncing off of the player and the instrument themselves as well as in our ear canal and in our neural interpretation of it. While noise can warp a signal and make it lose its meaning, noise is undeniably part of our appreciation of music.
Part of my research is looking at the signal of protein expression in living cells. Cells produce proteins to affect their internal and external environment, more of a particular kind of protein will cause a larger effect. However, like the Sydney opera house, living cells introduce noise into their signals. Protein production does not happen in a perfectly still and ordered universe like we imagined Beethoven in, and, like that musical signal, protein expression noise strikes a balance between distorting and countering the signal and modifying and receiving it. Understanding how cells, organisms that undergo evolution, construct themselves in response to and in the manipulation of their own environment is fundamental to fully understanding how life works at a cellular level.