In Angewandte's online release last Thu there was a lovely paper about AFM studies of the enzyme titin kinase (TK), which is naturally activated by pulling force, a bit like a christmas cracker, but reversibly (that bit was known, but I wasn't aware of it before).
Puchner and Gaub at the LMU Munich have done a three-step experiment involving
1) pulling to activate
2) allowing time to bind substrate
3) further pulling to analyse
In analogy to spectroscopic methods that involve "pumping" by laser light and then probing by spectroscopic measurement, they call this a "pump and probe" force experiment.
Intriguingly, they can see in the force measurements whether or not the substrate (ATP) has bound during phase 2. Plus, they can exactly define which energy barriers the pulling has to overcome to open the path for the enzyme activity.
Exploring the Conformation-Regulated Function of Titin Kinase by Mechanical Pump and Probe Experiments with Single Molecules
Elias M. Puchner, Hermann E. Gaub
Angew Chem Int Ed 2010
Published Online: Jan 13 2010 10:57AM