Difference Between Rate Zonal and Isopycnic Centrifugation

The key difference between rate zonal and isopycnic centrifugation is that rate zonal centrifugation is important in separating particles that differ in size but not in their density, whereas isopycnic centrifugation is important in separating particles that differ in density but not in their size.

Centrifugation is an analytical technique we can use to separate particles in a solution based on the size, shape, density, viscosity, etc. of the medium. Here, we need to place the solution containing the suspended particles in a centrifugal tube and then insert the tube into rotor in order to rotate it at a defined speed so that the particles will get separate from the solution.

CONTENTS

1. Overview and Key Difference
2. What is Rate Zonal Centrifugation
3. What is Isopycnic Centrifugation
4. Side by Side Comparison – Rate Zonal vs Isopycnic Centrifugation in Tabular Form
5. Summary

What is Rate Zonal Centrifugation?

Rate zonal centrifugation is an analytical technique we can use to separate particles of a solution depending on the size, but not on the density. In other words, this technique separates the particles from a solution based on the size, but it does not consider the differences in the density of the particles. Therefore, this technique is very useful in separating cellular organelles such as endosomes. Moreover, we can use it to separate proteins as well.

Furthermore, this centrifugation is time-dependent. This means the position of the sample relates to the time of sedimentation. The gradient we obtain from this method is flat, and the maximum density of this gradient never exceeds the density of the maximum dense particle in the pellet.

What is Isopycnic Centrifugation?

Isopycnic centrifugation is an analytical technique we can use to separate particles of a solution depending on the density, but not on the size. That means; we can separate particles in a solution if they are different from each other in their density. If they differ in size instead of density, then this technique is not suitable for that separation. The size of particles affects only the rate of migration of the particles. Therefore, this technique is independent of time.

More importantly, we can use this technique to separate nucleic acids in a gradient. The gradient given by isopycnic centrifugation is steep. Moreover, it does not produce a pellet because the separation is based on the buoyant densities of particles.

What is the Difference Between Rate Zonal and Isopycnic Centrifugation?

The key difference between rate zonal and isopycnic centrifugation is that the rate zonal centrifugation is important in separating particles that differ in size but not in their density, whereas the isopycnic centrifugation is important in separating particles that differ in density but not in their size.

Moreover, another significant difference between rate zonal and isopycnic centrifugation is that the rate zonal centrifugation is time-dependent, while the isopycnic centrifugation is independent of time. Besides, the gradient given by the rate zonal centrifugation is flat while in isopycnic centrifugation it is steep.

Summary – Rate Zonal vs Isopycnic Centrifugation

Centrifugation is an important analytical technique. There are two forms of centrifugation that we use in biological applications: rate zonal and isopycnic centrifugation. The key difference between rate zonal and isopycnic centrifugation is that the rate zonal centrifugation is important in separating particles that differ in size but not in their density, whereas the isopycnic centrifugation is important in separating particles that differ in density but not in their size.

Reference:

1. Dwivedi, Gaurav. “Home Exam Answers.” LinkedIn SlideShare, 20 May 2012, Available here.

Image Courtesy:

1. “Tabletop centrifuge” By Magnus Manske – Own work (CC BY 1.0) via Commons Wikimedia
2. “Density gradient” By The original uploader was Mlw3559 at English Wikibooks. – Transferred from en.wikibooks to Commons (CC BY-SA 2.5) via Commons Wikimedia