(A) Oligonuclotide sequences and folding schemes. R2APCW, three- stranded fold; CW, double-stranded hairpin; R2AP, single strand. 2-aminopurine is designated as a. At 0° C, in 0.5 M LiCl, 10 mM Na phosphate of Tris HCl buffer, pH8, the oligonucleotides has been proved to form the intramolecular folds shown here (9). (B) scheme of YOYO dye.