Stopped-flow Technique (CAT#: STEM-AC-0015-WXH)

This technique involves two reactants held in separate reservoirs that are prevented from freely flowing by syringe pumps. The reaction is initiated by depressing the reactant syringes, and thus releasing the reactants into the connecting "mixing chamber" where the solutions are mixed. The reaction is monitored by observing the change in absorbance of the reaction solution as a function of time. As the reaction progresses it fills the “stop syringe” which then expands until it hits a block at the point when the reaction has reached a continuous flow rate, thereby stopping the flow and the reaction, and thus allowing the researcher to calculate the exact initial rate of reaction.

Typically used to gain an understanding of reaction mechanisms, including drug-binding processes or following protein structural changes, stopped-flow spectroscopy enables the study of fast reactions in solution over timescales in the range of millisecond to hundreds of seconds.

1. In stopped-flow experiments, two, three, or four sample solutions are rapidly mixed and injected into an observation cell.
2. When the flow is stopped, the kinetics are recorded with a detector best suited to the chemical properties of the solutions and the information of interest (e.g. particle size, the environment of the fluorophore, chromophore).

Stopped-Flows