Difficulties Obtaining Genomic DNA

[MELANSOND]

***Hi -
***I'm seeking protocols for genomic DNA extraction from "difficult" 
***sources.  Thus far, standard Proteinase K methods (published in Current 
***Protocols and Maniatis) have failed miserably on the frozen tissues that 
***I'm using.  Commercial products, such as Bio 101's Genome kit and BRL's 
***DNAzol reagent work, albeit with limited success - low yield and DNA on 
***the order of 23 kb. 
***
***One explanation that I've been entertaining recently is that I'm being 
***hampered by extracellular matrix material.  Is it possible to get cells 
***apart with something like collagenase and still be able to inhibit 
***endogeneous intracellular DNAses?
***
***Thanks in advance
***Robert Schoenfeld
***Univ. Utah
***schoenfeld at med.utah.edu
***
***
Hi,	I realize you are probably working with animal cells, but how about
good old tissue grinding under liquid Nitrogen with a mortar and pestle.  If it
works for plant tissues (woody, polysaccharides, cellulose) it will probably
work for you.
Good Luck