Improved silica-guanidiniumthiocyanate DNA isolation procedure based on selective binding of bovine alpha-casein to silica particles

DNA purified from clinical cerebrospinal fluid and urine specimens by a sil ica-guanidiniumthiocyanate procedure frequently contained an inhibitor(s) o f DNA-processing enzymes which may have been introduced by the purification procedure itself. Inhibition could be relieved by the use of a novel lysis buffer containing alpha-casein. When the novel lysis buffer was used, alph a-casein was bound by the silica particles in the first step of the procedu re and eluted together with DNA in the last step, after which it exerted it s beneficial effects for DNA-processing enzymes, In the present study we ha ve compared the novel lysis buffer with the previously described lysis buff er with respect to double-stranded DNA yield (which was nearly 100%) and th e performance of DNA-processing enzymes.