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(CpCpTp ApCpG) and 5'-d(CpGpCpGpCpG) in aqueous salt solutions was studied by 1D- a nd 2D homonuclear PMR and heteronuclear H-1-P-31-spectroscopies. Signals fr om nonexchangeable protons of hexamers in NMR spectra were assigned using t he available 2M-TOCSY, 2M-NOESY, and H-1-P-31-(HMBS) spectra. The dependenc es of proton chemical shifts of deoxyhexanucleotides on concentration and t emperature were measured. In terms of the two-states model (monomer-duplex) , constants and thermodynamic parameters of self-association of hexamer mol ecules in solution were obtained based on these dependences. The values obt ained correlate well with theoretical values calculated using the model of the <<nearest neighbor>> for the formation of duplexes of sequences d(CGTAC G) and d(CGCGCG).