Chemical reactions in the living cell occur very quickly. It had therefore been challenging to observe them on a detailed level, and there were limitations in microscopically analyzing physiological reactions. However, the IBS Center for Plant Aging Research (Director Hong Gil Nam), in collaboration with Professor Richard N. Zare and his research team at Stanford University in the U.S., recently devised a way to observe the reaction process in very short time units. The core of this newly developed method is to accelerate micrometersized droplets to high speed and have them collide. Reactions occur in the fused droplets. Meanwhile, the fused droplets enter the heated capillary inlet of the mass spectrometer and are analyzed while chemical reactions are halted. By controlling the flight distance of the fused droplet before it enters the capillary, the research group was able to analyze the reaction kinetics at a microsecond timescale. Using this new method, the research group observed phenomena similar to biochemical reactions that occur in actual cells and they expects that this research will pioneer the new field of “microdroplet biochemistry.”

Kinetics of Acid-Induced Unfolding of Cytochrome c

The Center fused water droplets containing an acidic solution with water droplets containing cytochrome c by colliding them at high speed and measured the kinetics of acid-induced unfolding of cytochrome c with 3-μs temporal resolution. As a result, they discovered that cytochrome c rapidly unfolds during a short timescale of 50μs before slowing down (right).

Published paper

Jae Kyoo Lee et al., “Microdroplet fusion mass spectrometry for fast reaction kinetics”, PNAS. Vol. 112, no. 13, pp. 3898-3903 (2015)
Jae Kyoo Lee et al., “Acceleration of Reaction in Charged Microdroplets”, Quarterly Reviews of Biophysics, 15th JULY (2015)