Virus Purification and Concentration

Question 1

Why is the ultracentrifuge important for virology?

Answer 1

high speed of centrifugation can sediment even the smallest viruses

Question 2

rate-zonal centrifugation

Answer 2

sample is layered as narrow zone on the top of a density gradient (sucrose of different densities)

*particles move at different rates depending on mass

Question 3

T/F With rate-zonal centrifugation, the higher mass particles will be near the top.

Answer 3

F: they are fast sedimenting and will be on the bottom

Question 4

T/F Time is important for centrifuging because if you spin it too long everything will settle on the bottom.

Answer 4

T

Question 5

isopycnic point

Answer 5

point where buoyant density of a particle equals that of the surrounding density gradient medium

Question 6

buoyant density

Answer 6

if the object has exactly the same density as the fluid, then its buoyancy equals its weight; will remain submerged in fluid but won’t sink or float

Question 7

What are suitable density gradient media for isopycnic centrifugation?

Answer 7

sucrose or cesium chloride (better)

Question 8

T/F With isopycnic centrifugation, particles will never settle at the bottom of the tube no matter how long you centrifuge

Answer 8

T

Question 9

T/F with isopycnic centrifugation you place the sample on top of a density gradient before centrifugation

Answer 9

F you start with a uniform mixture of sample and density gradient -> particles will move until density is the same as surrounding medium (isopycnic point)

Question 10

membrane chromatography

Answer 10

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

• binding of viruses on ion exchange membranes depends on charge distribution on virus
• adsorption and elution of viruses achieved by anion or cation exchange membranes