A spectroscopic study of poly(dA–dT)·poly(dA–dT) in microemulsions

Abstract

The behaviour of high molecular weight [poly(dA–dT)·poly(dA–dT)] (polyAT) [(0.9–1.9)×10⁶ Da] in the quaternary water-in-oil microemulsion CTAB–n-pentanol–n-hexane–water has been studied as a function of temperature and NaCl concentration by means of UV and circular dichroism (CD) spectroscopy. Solubilization in the microemulsion stabilises the polymer double helix and no helix-to-coil thermal transition has been observed. At increasing NaCl concentration, the CD spectrum of polyAT exhibits dramatic changes and for salt concentrations 7.5×10⁻¹ M the spectral pattern suggests the formation of aggregates of the ψ(−) type. Condensation is induced by the peculiar characteristics of the aqueous core of the microemulsion. The condensates seem to destabilise the microemulsive system and, with time, separate from it.