title: 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 (H(c)(I))-->lamellar (L(c)(alpha))-->inverted hexagonal (H(c)(II)) transformation is found on increasing hexanol content. The H(c)(II) structure is converted into L(c)(alpha) on adding more DNA. Further increase in hexanol content leads to a phase separation in the surfactant solution, and a reentrant L(c)(alpha)-->H(c)(II)-->L(c)(alpha) 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.
authors.affiliation: Raman Research Institute, Bangalore 560 080, India.
authors.forename: Rema
authors.initials: R
authors.lastname: Krishnaswamy
authors.forename: V A
authors.initials: VA
authors.lastname: Raghunathan
authors.forename: A K
authors.initials: AK
authors.lastname: Sood
mesh_terms: D000077286:Cetrimonium; D002593:Cetrimonium Compounds / Q000737:chemistry*; D045424:Complex Mixtures / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D000441:Hexanols / Q000737:chemistry*; D046911:Macromolecular Substances; D009690:Nucleic Acid Conformation; D044367:Phase Transition; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry*; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D002593:Cetrimonium Compounds; D045424:Complex Mixtures; D000441:Hexanols; D046911:Macromolecular Substances; D012996:Solutions; D013501:Surface-Active Agents; D004247:DNA; D000077286:Cetrimonium