Reentrant phase transitions of DNA-surfactant complexes

Abstract

Complexes of double-stranded DNA with the cationic surfactant cetyltrimethylammonium bromide have been studied using small angle x-ray diffraction at varying concentrations of DNA and the cosurfactant hexanol. At low DNA concentrations, an intercalated hexagonal (HIc)-lamellar (L ac )-inverted hexagonal (HIIc ) transformation is found on increasing hexanol content. The HII c structure is converted into L a c on adding more DNA. Further increase in hexanol content leads to a phase separation in the surfactant solution, and a reentrant L a c-HII c -L a c transition is observed as DNA concentration is increased. Such structural transformations of DNA-surfactant complexes, driven by DNA concentration, have not been reported until now