Scheme 1. Upon ps Excitation, Native Enzyme, E(I), Undergoes a Sub-μs Transition to an Intermediate, E(II), That Is Attributed to an Ingress of Solvent Water(s).

This intermediate can either partition back to E(I) or evolve in a few μs to a new, structurally distinct intermediate, E(III); both processes are accompanied by an expulsion of water from the dimer interface.