What is stopped-flow spectroscopy?

Typically used to gain an understanding of reaction mechanisms including drug-binding processes, or to determine protein structure, stopped-flow spectroscopy enables the study of fast reactions in solution over timescales in the range of 1 millisecond to hundreds of seconds.

How does stopped-flow work?

Mechanism. The Stopped Flow technique works because within milliseconds of combining the two reactants the absorbance can be read. In addition, the stop syringe assures for a steady rate of flow pas the spectophotometer so that reactants are being added to solution and forming products at a consistant rate.

What is quench flow?

Small volumes of solutions are driven through a high efficiency mixer and flow into a delay (or ageing) loop. After a set time, the reaction is stopped (or quenched) by the addition of a chemical quench solution.

How does quenching stop a reaction?

Quenched Flow Approach In a quenched-flow instrument, the reaction is stopped after a certain amount of time has passed after mixing. For example, an enzyme-catalyzed reaction can be stopped by adding an acid, base, or salt solution that denatures (destroys the activity of) the protein enzyme.

What is continuous flow method?

Continuous-flow methods are a simple and efficient tool for monitoring the kinetics of chemical reactions in solution. After a reaction has been initiated by a mixing step, liquid flows down an observation tube while the reaction proceeds.

What are the techniques of flow method used for fast reaction?

Flow methods, continuous flow and stopped flow, both based on the rapid mixing technique, allow the investigation of enzyme reactions down to the millisecond range. Relaxation methods, temperature jump and pressure jump, make the microsecond range accessible.

What are slow reactions?

The slow reaction is defined as the reaction which takes longer time to complete. The slow reaction possesses a low rate of reaction. They possess higher activation energy. The example of slow reactions are rusting of a water pipe, a piece of newspaper turning yellow and so forth.

What is an example of a fast reaction?

Chemical reactions that complete in a very short time, such as less than 10 -6 seconds, they are called fast reactions. Examples: Magnesium ribbon is burnt in the flame of Bunsen burner; it quickly gets combusted with a noticeable spark. Similarly, a neutralization reaction between acids and bases is a fast reaction.

What is the main benefit of continuous flow?

The key benefits of continuous flow are; product of the reactions are removed from the irradiated area, problems of photon penetration depth and mixing can be largely avoided, reactions are safer as the volume of solvent in proximity to a hot lamp is significantly reduced.

What are some examples of slow reactions?

How do you know if a reaction is slow or fast?

The overall reaction rate depends almost entirely on the rate of the slowest step. If the first step is the slowest, and the entire reaction must wait for it, then it is the rate-determining step.

How is stopped flow used in the lab?

Stopped-flow is a lab technique for studying fast chemical reactions. A stopped-flow instrument is a rapid mixing device used to study the chemical kinetics of fast reactions in solution. The solutions are first forced from syringes into a mixing chamber. After perhaps a few milliseconds the observation cell is filled by…

What is the dead time of a stopped-flow system?

The volume injected is limited by the stop syringe which provides the “stopped-flow”. Just prior to stopping, a steady state flow is achieved. The solution entering the flow cell is only milliseconds old. The age of this reaction volume is also known as the dead time of the stopped-flow system.

How is the volume of a stopped flow solution limited?

Small volumes of solutions are rapidly driven from syringes into a high efficiency mixer to initiate a fast reaction. The resultant reaction volume then displaces the contents of an optical cell thus filling it with freshly mixed reagents. The volume injected is limited by the stop syringe which provides the “stopped-flow”.

How is stopped flow used in rapid kinetics?

Perhaps the most frequently used rapid kinetics techniques is stopped-flow. Small volumes of solutions are rapidly driven from syringes into a high efficiency mixer to initiate a fast reaction. The resultant reaction volume then displaces the contents of an optical cell thus filling it with freshly mixed reagents.