For one of our lab sessions, we had to isolate DNA from E. Coli bacteria. During one of the steps in the isolation process, we had to use SDS(Sodium lauryl sulfate) at 60°C. One of the questions was:
Why do we use SDS, and why at this temperature.
I already found out that SDS is a detergent, and is therefor helping to release intracellular components.
But why is it being used at 60°C?
I found most Websites said to heat the SDS at 60C but never saying WHY. Perhaps this statement will help you:
NA samples were heated in SDS at 60 C for 5 minutes to insure. complete disruption of virions by SDS and to avoid aggregation.
So it's some property in the SDS?
Sra
Thanks a lot! I appreciate all your help. It's really hard to find decent info about this subject.
The reason why SDS is used at 60°C during the DNA isolation process is because it helps in breaking down the cell membrane and denaturing proteins.
Let's break it down into two parts:
1. Breaking down the cell membrane: SDS is an anionic detergent that has a hydrophilic (water-loving) head and a hydrophobic (water-repelling) tail. When SDS is added to the cell suspension containing E. coli, it interacts with the lipid bilayer of the cell membrane. The hydrophobic tails of SDS insert between the lipid molecules of the membrane, disrupting its structure. This leads to the breakdown of the cell membrane, allowing the release of intracellular components, including DNA.
2. Denaturing proteins: Proteins present in the E. coli cells play a significant role in protecting and compacting the DNA. To access the DNA, it is crucial to denature these proteins. SDS, at elevated temperatures, aids in denaturing proteins by disrupting their tertiary and secondary structures. The hydrophobic tail of SDS interacts with the hydrophobic regions of proteins, causing them to unfold and lose their functional structure. The high temperature (60°C) accelerates this denaturation process, making it more efficient.
By using SDS at 60°C, the combination of the detergent action and elevated temperature helps to effectively break down the cell membrane and denature proteins, which enables the release and extraction of DNA from the E. coli cells.