Take the 2-minute tour ×
Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. It's 100% free, no registration required.

When applying this method we have a glass or plastic column of resin which is positively charged. Then we pour cell extract into the column in order to capture the negatively charged particles which include DNA.

After that we gradually add salt which neutralizes the molecules. But it does this gradually so strongly attached DNA molecules fall last while RNA and proteins fall first.

The question is why does DNA have a greater negative charge than RNA ?

share|improve this question
    
Perhaps this could be due to the size of the molecules? DNA is double stranded vs typically single stranded RNA and DNA is also more stable so would probably be longer. –  Bitwise Oct 22 '12 at 23:24
add comment

1 Answer 1

A longer or duplexed Nucleic acid will have more charge per mole of the molecule. But generally it is not the overall charge that matters in electrophoresis or MS or chromatography; it is the charge density and specific charge (z/m) that matters (charge density of a longer RNA will be almost same as smaller RNA. they will also have same specific charge)

The properties of stationary phase is very important in controlling the separation process. Without knowing what resin is used, it will be difficult to comment about why RNA is not retained. Sometimes the strong basicity of the stationary phase, such as in quaternary ammonium resins, degrades RNA by alkaline hydrolysis.

If yours is a commercial resin then you will have a tough time finding out what exactly it is made of. Unless of course you break the column open and do a molecular analysis of the resin :P

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.