Test 1 - Virus Purification (5)

Question 1

What are the different methods of centrifugation for virus purification?

Answer 1

• Rate-zonal centrifugation
• Isopycnic Centrifugation

Question 2

What kind tool uses enough gravitational force to efficiently sediment even the smallest viruses?

Answer 2

Ultracentrifuge

Question 3

Describe Rate-Zonal centrifugation.

Answer 3

The sample is layered as a narrow zone on the top of a density gradient, e.g. sucrose of different densities. Under cetnrifugal force, particles mmove at different rates depending on their mass.

This process is time sensitive.

Question 4

Describe Isopycnic centrifugation.

Answer 4

In isopycnic separation, also called buoyant or equilibrium separation, particles are separated solely on the basis of their buoyant density. By this method the particles will never sediment to the bottom of the tube, no matter how long the centrifugation time.

Question 5

Define buoyant density.

Answer 5

If the object has exactly the same density as the fluid, then its buoyancy equals its weight. It will remain submerged in the fluid, but it will neither sink nor float.

Question 6

Define isopycnic point.

Answer 6

The point where the buoyant density of a particle equals that of the surrounding Density Gradient medium.

Question 7

Describe virus purification with membrane chromatography.

Answer 7

The macroporous structure of the membrane allows large viruses to enter it and to bind to the inner pore surface easily.

Binding of the viruses on ion exchange membranes depends on charge distribution on the virus. Adsorption and subsequent elution of viruses can be achieved by anion or cation exchange membranes.