What is the Difference Between Differential and Density Gradient Centrifugation?

Differential and density gradient centrifugation are two types of centrifugation techniques used for separating particles in a mixture. The key difference between these two methods lies in the physical properties on which the separation process is based.

Differential Centrifugation:

• Separates cells and organelles based on their mass, size, and shape.
• More straightforward and simpler compared to density gradient centrifugation.
• Commonly used for the preparation of buffy coats from whole blood.

Density Gradient Centrifugation:

• Separates molecules and particles based on their density.
• Focuses on two characteristics: size and density.
• Involves the use of reagents with specific densities to isolate or separate cells, which can increase purity and throughput.

In differential centrifugation, particles in the analyte mixture move under centrifugal force until their density is similar to the surrounding medium, causing them to sediment. In contrast, density gradient centrifugation involves the rotation of the sample around a fixed axis, causing the production of a centrifugal force that moves the particles in the sample down through a liquid medium. The sedimentation of particles or cells with different sizes and densities at different rates allows for their separation.

Comparative Table: Differential vs Density Gradient Centrifugation

The main difference between differential and density gradient centrifugation lies in the physical properties they exploit for separation. Here is a table comparing the two methods:

• Differential Centrifugation: This method separates particles based on differences in mass, size, and density. As a result, particles with higher densities settle at the bottom, followed by less dense particles that form bands above the denser particles. It is commonly used for the separation of cell organelles and membranes, as well as for low-resolution separation of the nucleus.

• Density Gradient Centrifugation: This method focuses on separating cells based on their density, rather than mass and size alone. It can be further divided into rate-zonal and isopycnic centrifugation. In rate-zonal centrifugation, particles are separated based on their sedimentation coefficients, and they are obtained from the bottom of the tube through a series of fractions. In isopycnic centrifugation, particles move until their density is the same as the surrounding medium, resulting in the formation of distinct layers. This method is preferred for purifying subcellular organelles and macromolecules.

In summary, differential centrifugation separates particles based on their mass, size, and density, while density gradient centrifugation separates particles based on their density.