title: Thermodynamic behaviour of the heptadecadeoxynucleotide d(CGCGCGTTTTTCGCGCG) forming B and Z hairpins in aqueous solution.
abstract: UV and CD data of the partially self-complementary heptadecadeoxynucleotide d(CGCGCGTTTTTCGCGCG), obtained as a function of temperature, salt and strand concentration, show that: at low NaCl and strand concentration the oligomer exhibits, on increasing the temperature, a biphasic thermal profile which is indicative of two structural transitions, from dimeric duplex to hairpin and from hairpin to coil; the loop stabilizes enthalpically both B and Z hairpin structures with respect to the corresponding unconstrained hexamer d(CGCGCG) by a few Kcal/mol; the oligomer undergoes a B-Z transition which appears to be complete, at 0 degree C, when induced by NaClO4; by contrast the B-Z transition induced by NaCl does not reach completeness even at salt saturation. The independence of the denaturation temperature, at high salt conditions, on the oligomer concentration indicates that the Z structure is present also in the hairpin.
mesh_terms: D002942:Circular Dichroism; D004247:DNA; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009838:Oligodeoxyribonucleotides; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D014867:Water
chemical_list: D009838:Oligodeoxyribonucleotides; D014867:Water; D004247:DNA