|MadSci Network: Molecular Biology|
Well, there are a few questions that come to mind in regards to your case. First, what is the starting volume of blood? What are the different kits you have used, or what DNA isolation techniques? And why store the blood at 4 degrees C instead of -70 degrees? And last, what is the end use of the DNA? I can't do you much good without these facts because I might mention something you have tried already, and knowing what the DNA is going to be used for has implications on what type of protocol to use so that subsequent experiments aren't hindered. There are so many kits for blood isolation, but I have used the Qiagen DNeasy kit for genomic DNA isolation and it worked well. I'll tell you what though, there is a protocol I found on the web from Methods for DNA isolation from the University of Oklahoma Dept. of Chemistry and Biochemistry. They started out with blood stored at -70, so even though you added EDTA to your samples, it might not have been enough by itself to prevent degredation. However, it is too late for your old samples to worry about that. If you write to my e-mail address (firstname.lastname@example.org ) with some more specifics I might be of better service. In the meantime, see if this protocol helps.
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