frozen whole blood DNA isolation

[lakshb]

hi
does anyone have the protocol for frozen whole blood dna isolation?my blood samples are 1 month old and were stored in an ordinary freezer.i have to separate serum first in order to proceed further.does any one know how to separate serum from frozen samples?.becoz even after high speed centrifugation i was not able to separate the serum.

[danfive]

You need to find out if the samples were treated with heparin, EDTA, or sodium citrate, which will inhibit coagulation, without coagulation--no serum. Centrifuge at 3000g to remove cells, and you can use the plasma. if you don't care about the clotting factors, and fibrinogens in the protein mix it shouldn't matter.

If you've done high speed centrifugation and don't see a pellet, i.e. no cells or clots, then you are probably already working with serum. Most people prepare serum and separate it from the clot before freezing it.