Enthalpic pair wise self-interactions of four deoxynucleosides (dU, dC, dG, dT) in (dimethylsulfoxide + water) mixtures at T = 298.15 K

•Dilution enthalpies of 2′-deoxynucleosides in (DMSO + water) mixtures were determined.•Enthalpic coefficients (hxx) were calculated based on McMillan–Mayer’ theory.•The values of hxx are large negative cross the studied range of mixed solvents.•Hydrophilic interactions are proved to be prevailing in the ternary solutions.•The trends of hxx depend on the (hydrophobic / hydrophilic) equilibrium of solutes.

The dilution enthalpies of four 2′-deoxynucleosides, namely 2′-deoxyuridine (dU), 2′-deoxycytidine (dC), 2′-deoxyguanosine (dG) and 2′-deoxythymidine (dT), in (dimethylsulfoxide (DMSO) + water) mixtures of various mass fractions (wDMSO = 0 to 0.30) have been determined at T = 298.15 K, respectively, using an isothermal titration calorimeter (ITC200 MicroCal). On the basis of McMillan–Mayer’ theory, enthalpic pair wise self-interaction coefficients (hxx) of each compound at different values of wDMSO have been evaluated from successive dilution enthalpies. It was found that the values of hxx are all large negative and increase gradually with wDMSO across the whole composition range of the mixed solvent studied, though the degree of variation among them is somewhat different. The results indicate that (hydrophilic + hydrophilic) interactions are prevailing over (hydrophobic + hydrophobic) and (hydrophobic + hydrophilic) interactions in the ternary aqueous solutions under study.

Graphical abstractEnthalpic pairwise self-interaction coefficients (hxx) of the four 2′-deoxynucleosides are of uneven increasing magnitudes (■, 2′-deoxyuridine; , 2′-deoxycytidine; , 2′-deoxyguanosine; , 2′-deoxythymidine).Figure optionsDownload full-size imageDownload as PowerPoint slideFigure optionsDownload full-size imageDownload as PowerPoint slideFigure optionsDownload full-size imageDownload as PowerPoint slideFigure optionsDownload full-size imageDownload as PowerPoint slide