In these papers
- A rapid non-enzymatic method for the preparation of HMW DNA from blood for RFLP studies
- A simple salting out procedure for extracting DNA from human nucleated cells
- Modified salting-out method: high-yield, high-quality genomic DNA extraction from whole blood using laundry detergent.
In brief, red blood cells are first reduced/removed. Nucleated cells are lysed in the presence of SDS and genomic DNA are released. The resultant lysate are gooey. Addition of NaCl results in protein precipitation which is then removed by centrifugation. The genomic DNA is believed to not be precipitated by salt and thus remain in the supernatant which is recovered by ethanol/propanol precipitation.
Typically, ~30 µg of DNA is obtained per mL of blood.
I tried the salting out method recently and the yield is quite low (~ 10 µg per mL of blood), so no where near the published figure. In comparison, I obtained ~ 30 µg using phenol/chloroform from the same blood sample. I have tried using NH4Cl and still get a low DNA yield. I believe one of the reasons is that a lot of genomic DNA get trapped in the protein precipitates after addition of salt.
What can be done to prevent or minimise genomic DNA being trapped with the protein precipitate?