The hydrogen/deuterium exchange (HDX) method is useful to analyze kinetics of large macromolecular complexes, although its time resolution requires further improvement. A newly developed micro-reactor chip was made of polydimethylsiloxane with a 100-μm deep and wide microchannel. The channel in the chip has two mixing points of Y-shaped flow and allowed us to shorten time durations from the start to quenching for the HDX in 70S ribosome with high temporal resolution. This device enabled us to quench the deuterium incorporation at as early as 20 ms, detecting structural changes of individual ribosomal proteins in solution at the time scale comparable to a single reaction cycle for the peptide elongation. The profile of deuterium incorporation in individual proteins of the complex was superimposed on the X-ray crystal structure to depict the surface HDX map, revealing localization of protein movement in the ribosome. The current method serves as a useful method to visualize the regional movement of large macromolecules with high temporal resolution sufficient to examine protein dynamics.
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