The kinetic isotope effect aids in the design of “analogues” to these structures, such as the inhibitors oseltamivir and saquinavir. The ratio of energies for two of these structures formed by rapidly-interconverting molecules is the focus of the Curtin–Hammett principle. (10[1])Ahmed Zewail won the Nobel Prize in Chemistry for observing some of these structures using pump-probe spectroscopy. The configurations of these structures in space are the subject of Hammond’s (10[1])postulate. (10[1])Double daggers denote these (10[1])structures, (10[1])which are (10[1])formed at the saddle points (10[1])of potential energy surfaces. For 10 points, the activation energy must be reached to form what short-lived (10[1])structures that appear at local energy maxima on a reaction coordinate diagram? ■END■ (10[1])