Following the dynamics of protein conforma-tional changes over the relatively long periods of time typical of enzyme kinetics can be challenging. Choi et al. (p. 319; see the Perspective by Lu) were able to observe changes in lysozyme conformation, which changes its electrostatic potential, by using a carbon-nanotube field-effect transistor. Slower hydrolysis steps were compared with faster, but unproductive, hinge motion, and changes in lysozyme activity that occur with pH were shown to arise from differences in the relative amount of time spent in processive versus nonprocessive states.
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