DNA folding to form the loop - (Mar/15/2009 )

Dose any one know or some paper introduced

How many DNA base need for a loop, to fold to form a stem. Like a haparin ?

3-4 are enough, although the stem pair nearest the loop may not bind well.

IDT have a Oligo Analyzer in there SciTool that predicts hairpins.
Input your primer sequence and it will show you the hairpin.