Free or moving boundary electrophoresis is a type of electrophoresis technique that relies on the movement of a sharp boundary between a solution containing the analyte (the substance of interest) and a buffer solution. This technique was developed by Arne Tiselius in the 1930s and earned him the Nobel Prize in Chemistry in 1948.
Here's how it works:
1. Preparation: A solution containing the analyte is layered on top of a buffer solution in a vertical glass tube. The two solutions have different refractive indices, creating a visible boundary.
2. Electrophoresis: An electric field is applied across the tube. The charged analyte molecules migrate towards the electrode with the opposite charge.
3. Migration: The analyte molecules move through the buffer solution, creating a moving boundary that can be observed using Schlieren optics. This technique uses light refraction to visualize the boundary and measure its movement.
4. Analysis: The migration rate of the boundary is proportional to the analyte's electrophoretic mobility, which is determined by its charge and size. This information can be used to identify and quantify different components in the analyte mixture.
Key features of free or moving boundary electrophoresis:
* No supporting medium: The analyte migrates through a liquid buffer, unlike other electrophoresis techniques that use gels or membranes.
* Sharp boundary: The presence of a distinct boundary allows for precise measurement of the analyte's migration.
* Quantitative analysis: The technique is suitable for quantitative analysis of different components in a mixture.
* Limited resolution: Compared to other electrophoresis techniques, moving boundary electrophoresis has a limited resolution for separating complex mixtures.
Applications:
* Protein characterization: Determining the purity and homogeneity of protein solutions.
* Isoelectric focusing: Identifying the isoelectric point of proteins.
* Serum protein analysis: Studying the composition of serum proteins in clinical applications.
Limitations:
* Limited resolution: Compared to other techniques, it has a lower resolving power for complex mixtures.
* Technical challenges: Requires specialized equipment and precise experimental conditions.
* Time-consuming: The process can be relatively time-consuming.
Modern techniques:
While free or moving boundary electrophoresis was a significant breakthrough in its time, it has been largely replaced by more sophisticated and versatile electrophoresis techniques, such as gel electrophoresis and capillary electrophoresis. These techniques offer higher resolution, simpler operation, and wider applicability.
However, the historical significance of free or moving boundary electrophoresis remains as it paved the way for the development of modern electrophoresis techniques that are widely used in various fields today.
