Chemical synthesis occurs more readily if the reaction takes place inside micrometre-sized compartments.

In theory, it is difficult to merge two molecules into one because of the decrease in entropy as the reaction proceeds. To overcome this hurdle, Andrew Griffiths at Strasbourg University in France and his colleagues studied chemical reactions occurring inside tiny water droplets suspended in oil.

They found that a fluorescent molecule built from two reagents formed more quickly in smaller droplets of water. A mathematical model indicated that molecules landing on a droplet's internal surface are more likely to merge with each other because the surface limits the available space and constrains the reactants' freedom of movement.

The results suggest that compartments, such as aerosol droplets or the pores in hydrothermal vents, could have assisted the organic reactions that are thought to have led to the origin of life.

Phys. Rev. Lett. 112, 028310 (2014)