Quantum in se est
Ever felt a little incoherent? Or maybe you’ve been in two minds about something, or even in a bit of delicate state. Well, here’s your excuse: perhaps you are in thrall to the strange rules of quantum mechanics. (…)
On one level, you might think, we shouldn’t be surprised that life has a quantum edge. After all, biology is based on chemistry, and chemistry is all about the doings of atomic electrons - and electrons are quantum-mechanical beasts at heart. That’s true, says Jennifer Brookes, who researches biological quantum effects at Harvard University. “Of course everything is ultimately quantum because electron interactions are quantised.”
On another level, it is gobsmacking. In theory, quantum states are delicate beasts, easily disturbed and destroyed by interaction with their surroundings. So far, physicists have managed to produce and manipulate them only in highly controlled environments at temperatures close to absolute zero, and then only for fractions of a second. Finding quantum effects in the big, wet and warm world of biology is like having to take them into account in a grand engineering project, says Brookes. “How useful is it to know what electrons are doing when you’re trying to build an aeroplane?” she asks.
Take smell, Brookes’s area of interest. For decades, the line has been that a chemical’s scent is determined by molecular shape. Olfactory receptors in the nose are like locks opened only with the right key; when that key docks, it triggers nerve signals that the brain interprets as a particular smell.
Is that plausible? We have around 400 differently shaped smell receptors, but can recognise around 100,000 smells, implying some nifty computation to combine signals from different receptors and process them into distinct smells. Then again, that’s just the sort of thing our brains are good at. A more damning criticism is that some chemicals smell similar but look very different, while others have the same shape but smell different. The organic compounds vanillin and isovanillin, for example, smell differently but are two similarly shaped arrangements of the same molecule.
There is an alternative explanation. Around 70 years ago, even before the lock-and-key mechanism was suggested, the distinguished British chemist Malcolm Dyson suggested that, just as the brain constructs colours from different vibrational frequencies of light radiation, it interprets the characteristic frequencies at which certain molecules vibrate as a catalogue of smells.
photo { Steven Brahms }
