I would like to know how double stranded DNA becomes single stranded when binding to nitrocellulose membrane in southern blots. Does it require a special reagent? Is denaturing a special property of the membrane itself?
The DNA is denatured in-gel prior to transfer using alkali conditions, most commonly a solution containing 0.5 M NaOH (buffered with 1.5 M NaCl). Following that the pH of the gel is neutralised in 0.5 M Tris-HCl, pH 7.5; 1.5 M NaCl.
I have found the Roche DIG application manual to be a well-written and reliable resource for performing Southern and Northern blots. The section on Southern blots starts at page 94 and you can modify the protocol to suit other detection systems.
No, there is no such property present in membrane. After transferring to membrane they treat with alkaline solution to denture dsDNA to ssDNA for binding of probe.