Monday, April 17, 2006

Quantum biology

Aeons ago, my biophysical chemistry lectures used to speculate about electron flows along the double helix. Now the hot topic is quantum tunneling of protons catalyzing biological reactions:
Biochemistry | Evolving enzymes |

IMAGINE hitting a tennis ball against a wall. Time after time, the ball bounces back. But, just occasionally, the ball disappears only to reappear on the other side of the wall. The wall is solid; no bricks are missing. It sounds surreal, but in the weird world of quantum mechanics such occurrences, involving very small objects over very short distances, are an everyday effect known as quantum tunnelling.

Whether such an effect could account for odd behaviour at larger sizes and distances has long been the subject of debate... The answer, reported in this week's issue of Science, is that enzymes also exploit this quantum-mechanical loophole.

The researchers, based at the University of Manchester and the University of Bristol, both in Britain, studied a compound called tryptamine ... an enzyme called aromatic amine dehydrogenase (AADH) removes hydrogen from tryptamine.

Hydrogen, the simplest atom, consists of a single proton encircled by a single electron. As electrons are point-like, their quantum mechanical behaviour is well known. But protons are far bigger, and the idea that they might be able to quantum tunnel is more controversial. Yet the AADH catalyses the breakage of the otherwise very stable, carbon-hydrogen bond at ambient temperatures, a feat that would appear to be impossible.

... the British researchers raise the possibility that short-range tunnelling in enzymes might be the result of evolutionary pressure...
Well, if it does happen, what would it arise from other than evolutionary pressures? That last sentence is an odd exception to a well done article.

It all seems very improbable, but if it is physically possible, then I suppose natural selection would come up with a solution. Maybe this is what was going on during that vast period of time between the cooling of the earth and the rise of the organism -- perhaps "solving" the puzzle of quantum catalysis is a much harder problem than going from a bacteria to a naked ape.

There's a historical angle. I dimly recall that Schrodinger and some colleagues speculated about a quasi-mystical quantum mechanical "spark" to life and consciousness; some more recent books have continued the trend. Ineffable quantum phenomemon is the geek alternative to the Soul. It would be amusing if this turned out to be, in some sense, true.

But can I trust The Economist on this? They recently wrote an article on GeneDupe's plan to create living versions of mythological monsters:
PAOLO FRIL, chairman and chief scientific officer of GeneDupe, based in San Melito, California, is a man with a dream. That dream is a dragon in every home...
I didn't blog on that one as I simply figured The Economist had been duped by some whacko; indeed I barely skimmed it. Alas, this week they revealed, through the title above a letter to the editor, that I ought to have thought about what the letters in the name PAOLO FRIL could also spell. Really, they are not trustworthy.

PS. If enzymes really can quantum tunnel protons, there will be some novel industrial applications of the technique. It would not be the first time the 'blind watchmaker' has taught we sighted watchmakers.

PPS. My second son promises that when he grows up, he will bring mythical monsters to life and resurrect beasts long extinct. Heck, maybe he'll do me too ...

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