Question

WHAT I THE ROLE OF SDS REAGENT IN NUCLEIC ACID ISOLATION?

Answer 1

I've personally never used SDS for doing nucleic acid electrophoresis, but I use it instead for proteins. When that said, the role of SDS is to create what you could call a negatively charged soap around the protein insuring that the protein becomes predominantly negatively charged.

As electrophoresis depends on the gel casting, mass and charge density, it happens that the gel casting remains constant (that is, how hard is it for the protein to move through the gel), and the charge density is also constant (as we have treated the protein with the soap to become predominantly negatively charged), the only remaining variable is the mass. So based on this treatment we can separate proteins on mass.

Now here comes my concern about about nucleic acid and SDS:
I would say that it is not required to use SDS for nucleic acid electrophoresis, as the negatively charged phosphate backbone would be making up the for the charge density. The only reason I could guess you would use SDS is for denaturnation reasons, but way better regents comes into my mind. The reason you want to "denature" your nucleic acid is due to that different topology runs faster or slower on a gel, making the gel unable to serve as mass indicator.

Answer 2

In the lysis process, SDS is used to dissolve the lipid components of the cell envelope - it also denatures proteins. It's often used together with NaOH.