Cation-dependent transition between the quadruplex and Watson-Crick hairpin forms of d(CGCG3GCG)

The DNA oligonucleotide d(CGCG 3 GCG) can form either a Watson-Crick (WC) hairpin or a parallel-stranded quadruplex structure containing six G-quartet base pair assemblies. The exchange between these forms and single strands can be monitored using circular dichroism (CD). NMR results verified the assignment of specific CD bands to quadruplex and hairpin species, respectively