title: Hydrodynamic properties of DNA and DNA-lipid complex in an elongational flow field.
abstract: The aim of this study was to determine the difference between hydrodynamic properties of DNA-cetyltrimethylammonium (CTA) complex and those of DNA, which may be related to the difference in fibre-forming ability of DNA-CTA from that of DNA. Responses of DNA and DNA-CTA complex to an elongational flow field were investigated. In both solution systems, results suggesting a coil-stretch transition were obtained. From a critical strain rate value, the radius of gyration of DNA-CTA molecules in ethanol-glycerol solution was revealed to be 0.3-0.5 times of that of DNA in aqueous NaCl solution. Shear viscosity of DNA-CTA solution was much smaller than that of DNA solution, also suggesting a smaller size of DNA-CTA in ethanol-glycerol solution than that of DNA in aqueous NaCl solution. The plateau birefringence value of the DNA-CTA system, a parameter that indicates the local molecular conformation and the molecular arrangement, was only about 1/10 of that of the DNA system. There is an empirically determined molecular model of DNA-CTA complex in which a DNA molecule is sheathed by a cylindrical crust made of CTA chains. This structure reduces the DNA molecular density in a pure elongational flow field region but cannot explain the observed reduction of birefringence intensity. The small plateau birefringence value of DNA-CTA compared with that of DNA was attributed to the reduced molecular polarizability by the particular conformation of DNA molecules and CTA chains in the DNA-CTA system such as that expected by the conformational models.
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan. nasa5131@sci.hokudai.ac.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Sasaki
authors.forename: Hidetomo
authors.initials: H
authors.lastname: Ashitaka
authors.forename: Kenji
authors.initials: K
authors.lastname: Ohtomo
authors.forename: Akimasa
authors.initials: A
authors.lastname: Fukui
mesh_terms: D000818:Animals; D016880:Anisotropy; D001718:Birefringence; D002593:Cetrimonium Compounds / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D012474:Salmon; D012996:Solutions; D012997:Solvents; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D002593:Cetrimonium Compounds; D008055:Lipids; D012996:Solutions; D012997:Solvents; D014867:Water; D004247:DNA