NMR investigation of self-association of deoxyhexanucleotides 5′-d(CpGpTpApCpG) and 5′-d(CpGpCpGpCpG) in aqueous solution

The self-association of deoxyribohexanucleoside pentaphosphates 5'-d(CpCpTpApCpG) and 5'-d(CpGpCpGpCpG) in aqueous salt solutions was studied by 1D- and 2D homonuclear PMR and heteronuclear H-1-P-31-spectroscopies. Signals from nonexchangeable protons of hexamers in NMR spectra were assigned using the available 2M-TOCSY, 2M-NOESY, and H-1-P-31-(HMBS) spectra. The dependences of proton chemical shifts of deoxyhexanucleotides on concentration and temperature were measured. In terms of the two-states model (monomer-duplex), constants and thermodynamic parameters of self-association of hexamer molecules in solution were obtained based on these dependences. The values obtained correlate well with theoretical values calculated using the model of the <<nearest neighbor>> for the formation of duplexes of sequences d(CGTACG) and d(CGCGCG).