title: Structure of the complex monolayer of gemini surfactant and DNA at the air/water interface.
abstract: The properties of the complex monolayers composed of cationic gemini surfactants, [C(18)H(37)(CH(3))(2)N(+)-(CH(2))(s)-N(+)(CH(3))(2)C(18)H(37)],2Br(-) (18-s-18 with s = 3, 4, 6, 8, 10 and 12), and ds-DNA or ss-DNA at the air/water interface were in situ studied by the surface pressure-area per molecule (π-A) isotherm measurement and the infrared reflection absorption spectroscopy (IRRAS). The corresponding Langmuir-Blodgett (LB) films were also investigated by the atomic force microscopy (AFM), the Fourier transform infrared spectroscopy (FT-IR), and the circular dichroism spectroscopy (CD). The π-A isotherms and AFM images reveal that the spacer of gemini surfactant has a significant effect on the surface properties of the complex monolayers. As s ≤ 6, the gemini/ds-DNA complex monolayers can both laterally and normally aggregate to form fibril structures with heights of 2.0-7.0 nm and widths of from several tens to ~300 nm. As s > 6, they can laterally condense to form the platform structure with about 1.4 nm height. Nevertheless, FT-IR, IRRAS, and CD spectra, as well as AFM images, suggest that DNA retains its double-stranded character when complexed. This is very important and meaningful for gene therapy because it is crucial to maintain the extracellular genes undamaged to obtain a high transfection efficiency. In addition, when s ≤ 6, the gemini/ds-DNA complex monolayers can experience a transition of DNA molecule from the double-stranded helical structure to a typical ψ-phase with a supramolecular chiral order.
authors.affiliation: Key Laboratory for Advanced Materials and Department of Chemistry, East China University of Science and Technology, Shanghai 200237, P. R. China.
authors.forename: Qibin
authors.initials: Q
authors.lastname: Chen
authors.forename: Xueli
authors.initials: X
authors.lastname: Kang
authors.forename: Rong
authors.initials: R
authors.lastname: Li
authors.forename: Xuezhong
authors.initials: X
authors.lastname: Du
authors.forename: Yazhuo
authors.initials: Y
authors.lastname: Shang
authors.forename: Honglai
authors.initials: H
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Hu
mesh_terms: D000388:Air; D002412:Cations; D004247:DNA / Q000737:chemistry*; D015316:Genetic Therapy; D013057:Spectrum Analysis; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D014162:Transfection; D014867:Water
chemical_list: D002412:Cations; D013501:Surface-Active Agents; D014867:Water; D004247:DNA