Spectroscopic study of polynucleotides in cationic w/o microemulsion.

Water has an active and key role in determining the structure of DNA. Entrapment of DNA and of synthetic model polynucleotides in reverse micelles, where the water activity can easily be modulated, may be a useful way of assessing the influence of water on DNA characteristics; it may also offer useful ideas on the problem of how the giant DNA molecule can be confined in the limited space of cell nuclei. The quaternary microemulsion CTAB n-hexane|n-pentanol| water was used to entrap calf thymus DNA, and the model polynucleotides single-strand polyA, single-strand polyT and duplex polyAT. Ultraviolet spectros-copy, specifically the band at 260 nm, was used to compare the pairing of complementary single-strand polynucleotides, and the dilution behaviour of native DNA and duplex polyAT in buffer solutions and in microemulsions. While pairing appears to occur to the same extent in both the microemulsive system and the buffer solution, dilution experiments show an influence from the different media. Confinement of the polynucleotides within micelles causes a hyperchromic effect, increasing with dilution, relative to the solutions. This effect has, on a preliminary basis, been attributed to denaturation of segments of the macromolecular duplex.