Differential/isopycnic/rate zonal centrifugation

[jones106]

Hey guys, I'm a little confused about these types of centrifugation. Here is what I know about them: Differential centrifugation is a good way to roughly separate cellular components based on their sedimentation coefficient (which is based on mass and shape). Larger and more massive components will sediment at lower speeds, while smaller components require higher centrifugal force.
Isopycnic uses a gradient of CsCl to separate based on buoyant densities. More dense components will equilibrate in the more dense regions of the CsCl while the less dense components will equilibrate in the less dense regions of the CsCl.
Rate zonal separates components based on their S-value, which determines how quickly the particles under investigation will move through a sucrose gradient.

First of all, do I basically have the right idea about these methods?
Secondly, the book we are using in Biochem. doesn't say much about these methods, so I turned to my old Cell Bio. book. This book seems to imply that Isopycnic and Rate Zonal are only used for separating nucleic acids. Can these methods be used for separating proteins from other proteins?

Sorry for the long-windedness, but I just feel like I am missing something important here. Sorry again, I just realized I posted this in the wrong place.

Thanks in advance,
Taylor

 

[jim mcnamara]

You have the right basic idea.

IMO:
The reason for the separation (no pun itended) of the methods is somewhat historical. Early RNA researchers, like Dubin and others, used stratified sucrose and then reported distibutions of particles over time. Once they standardized times, densities, and g forces, they knew they were talking, more or less, about similar nucleic acid extracts.

You can use any method you want, but reporting results and correlating what you get with other research requires using the same methods as the original research - or developing some clearly reproducible way of doing comparisons between your data and somebody else's. Which basically means you'd have to duplicate somebody else's research data using your methods, I guess.

There are other standard ways of reporting on protein extracts, as I recall.

 

[BoomBoom]

Can these methods be used for separating proteins from other proteins?

I believe column chromatography is the preferred method for doing this.