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Single-molecule dynamics in biomolecules. When isolated, the F1 part of ATP synthase hydrolyzes ATP, leading to rotation of its shaftlike g subunit within an ab-trimer. The system has a threefold rotational symmetry, and the g subunit is therefore expected to rotate by discrete 120° steps. Because of the stochastic nature of the motion, single-molecule techniques are required to resolve these individual steps. Yasuda et al. (10) attached a fluorescent molecule or gold bead to individual protein molecules and imaged them with a laser dark-field microscope and an ultrafast camera, allowing the 120° jumps of individual molecules to be observed on the submillisecond time scale. At low ATP concentrations, each 120° step can be resolved into substeps of 90° and 30°, which correspond to ATP binding and the release of the hydrolysis products, respectively (10).


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Volume 292, Number 5522, Issue of 1 Jun 2001, p. 1671.
Copyright © 2001 by The American Association for the Advancement of Science.