Study of self-association of molecules of deoxyhexanucleotides 5'-d(CpGpTpApCpG) and 5'-d(CpGpCpGpCpG) in water solutions by NMR

The self-association of deoxyribohexanucleoside pentaphosphates 5'-d(CpGpTpApCpG) and 5'-d(CpGpCpGpCpG) in aqueous salt solutions was studied by 1 D- and 2 D homonuclear PMR and heteronuclear 1H-31P-spectroscopies. Signals from nonexchangeable protons of hexamers in NMR spectra were assigned using the available 2M-TOCSY, 2M-NOESY, and 1H-31P-(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).