Researchers in the US have come a step closer to understanding how some of the earliest biochemistry on Earth began.

In nature, there are few ambidextrous biomolecules. For example, all amino acids are left-handed (L) and all sugars are right-handed (D). The opposite hand, or enantiomer, is often biologically inactive or even toxic. How did this preference come about? Graham Cooks and his group think it could all be down to one simple amino acid - serine.

Research by Cooks' group over the past eight years has revealed serine to be unique. When examined in a mass spectrometer in the vapour phase, serine clusters together in groups of eight molecules. These clusters are all made up of the same enantiomer, a phenomenon known as homochiral clustering. 

Cooks has now found that serine can spontaneously increase the amount of one enantiomer on sublimation. This is the first time that vaporizing a solid and then recrystallizing it has been shown to affect the enantiomeric composition of an amino acid.

Cooks explained that there would have been both (D)- and (L)-serine available in the prebiotic world. However, a tiny excess of L is likely, because it is slightly more stable than D. According to Cooks, once the symmetry is broken, serine can take care of the rest, turning all other serine molecules into the L conformation. Cooks' group have also shown that serine could then have passed this conformational preference onto other biomolecules, accounting for the biochemistry we know today. 

'This work could turn out to be very important,' said David Clemmer, an expert in analytical science at Indiana University, Bloomington, US. 'This adds to the mounting evidence that some amino acid clusters appear to be especially stable, readily formed and should be considered in models that aim to explain homochirogenesis.'  

Cooks' group are currently trying to study serine in more complex and realistic conditions, but Cooks believes the hypothesis is right. 'It's not a question of the science anymore, we just have to get the conditions right in the lab.'

May Copsey