A transition state holds a pose

Abstract

Transition States The transition state of a chemical transformation is inherently fleeting because the structure is high in energy. Nonetheless, Pearson et al. trapped a classical example of a bond rotation transition state using a modified protein (see the Perspective by Romney and Miller). The biphenyl molecule passes through an energy maximum when its rings rotate through a parallel position. A pocket within the editing domain of threonyl–transfer RNA synthetase was modified to stabilize parallel biphenyl rings, allowing further characterization of this normally transient structure. Science , this issue p. [863][1]; see also p. [829][2] [1]: /lookup/doi/10.1126/science.aaa2424 [2]: /lookup/doi/10.1126/science.aaa5623