Flash photolysis is a fast assay technique using lasers to break specific bonds in a reactant. This allows the reaction dead time to be reduced further, as all the reactants are mixed, but not able to react.
Caged ATP is a chemically modified form of ATP that can be ‘activated’ by exposing it to a specific wavelength of radiation. Reactions that are ATP-dependent, such as transport proteins in cell membranes, can be studied in this way. Many other ‘caged’ molecules, which are photoactivatable, are available, including nucleotides.