What is Gel-Chromatography?

Points to Remember:

• Gel chromatography is a separation technique.
• It separates molecules based on size and shape.
• It uses a porous gel matrix.
• Applications span various scientific fields.

Introduction:

Gel chromatography, also known as size-exclusion chromatography (SEC), is a powerful analytical technique used to separate molecules based on their size and shape. Unlike other chromatography methods that rely on interactions between the molecule and the stationary phase (e.g., ion exchange chromatography), gel chromatography separates molecules based solely on their ability to enter the pores of a gel matrix. Smaller molecules penetrate the pores more readily and thus have a longer path to travel through the column, eluting later than larger molecules which are largely excluded from the pores and travel a shorter, faster path. This makes it a valuable tool in biochemistry, biotechnology, and various other scientific disciplines.

Body:

1. The Gel Matrix:

The heart of gel chromatography lies in its stationary phase: a porous gel matrix. These gels are typically composed of cross-linked polymers, such as dextran (Sephadex), agarose (Sepharose), or polyacrylamide. The pore size distribution within the gel is crucial; it determines the separation range of the technique. Gels are available with a wide range of pore sizes, allowing for the separation of molecules ranging from small ions to large proteins and even macromolecular complexes. The choice of gel depends on the size range of the molecules to be separated.

2. The Separation Mechanism:

As a sample mixture is applied to the top of the chromatography column packed with the gel, molecules begin to migrate through the column. Larger molecules, exceeding the pore size of the gel, are excluded from the pores and travel primarily through the spaces between the gel beads. Smaller molecules, however, can enter the pores, resulting in a longer path length and slower migration. This difference in path length leads to the separation of molecules based on their size. The elution profile, showing the concentration of molecules versus elution volume, provides information about the size distribution of the sample.

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