J. Am. Chem. Soc. doi: 10.1021/ja800180u (2008)

Chemists have measured how much a bond between two atoms stretches in the transition state, which is the short-lived phase between the initial and end states in a chemical reaction.

Sri Rama Koti Ainavarapu and Julio Fernandez at Columbia University in New York and their colleagues developed a force clamp technique to use in 'single-molecule force spectroscopy'. Using this, they held onto individual molecules and stretched them so as to trigger the reduction of a disulphide bond in a protein, invoking the transition state of the reaction. The researchers could then measure the distance between the sulphur atoms as they stretched apart.