A spectroscopist tells how the tools of his trade are revealing quantum effects in biological molecules.

In introductory quantum mechanics, one learns that particles can behave like waves, with each particle having a wavelength inversely proportional to its momentum. I am fascinated by recent work that examines how, at the molecular level, life takes advantage of these wave-like properties.

The effects aren't visible when moving biomacromolecules are viewed whole, because their large mass means they have a negligibly small 'de Broglie' wavelength. However, atoms and electrons within a molecule — for example, in active sites, where reactions such as catalysis and light-absorption take place — may interact in a wave-like way.

Researchers are thus investigating what role the wavefunctions of these molecular constituents have during biochemical reactions. And if they do interact, over what distance and for how long does the wavefunctions' phase relationship, or quantum coherence, persist?

Spectroscopists have found evidence for coherences in a few biological systems, thanks to a technique known as multidimensional spectroscopy (A. Nagy et al. Curr. Opin. Struct. Biol. 16, 654–663; 2006). This involves tracking changes in a molecule's configuration over very short timescales with laser pulses that last femtoseconds (10−15 s).

Further results reported this year suggest that the energy transfer in a photosynthetic system is wave-like (G. S. Engel et al. Nature 446, 782–786; 2007). For this process, the quantum coherence of the light-excited charges may help the charges search out an efficient pathway through the molecule, by means of a mechanism analogous to a quantum computation.

This observation provokes a question that I look forward to seeing answered. Might biological systems have evolved to use matter's wave-like properties to optimize their efficiency?

Discuss these papers at http://blogs.nature.com/nature/journalclub