PolyAT chemical denaturation in w/o microemulsion

CD and UV spectroscopies have been used to investigate the effects caused by the addition of either strong acid-or base-containing microemulsions on the behaviour of the synthetic polynucleotide polyAT entrapped in the aqueous core of a cationic quaternary water-in-oil microemulsion (µE). The titrations were performed in the presence of variable concentrations of NaCl, in the range 0.00 to 0.60 M. In both cases, the primary effect was the reversible transition from B-double helix to random coil of the guest polynucleotide. However, in the microemulsive medium, the number of moles of protons (RH) and hydroxide ions (ROH) per mole of titrable sites are independent of the salt concentration but larger than 0.5, the value predicted on the basis of the stoicheiometry of the protonation-deprotonation processes. This result is in contrast with that obtained in aqueous solution (higher RH and ROH values and strongly dependent on NaCl concentration) and is explained with the presence of the cationic micellar wall (CTAB polar heads) acting as a ionic strength buffer.