title: Auto-assembly of nanometer thick, water soluble layers of plasmid DNA complexed with diamines and basic amino acids on graphite: Greatest DNA protection is obtained with arginine.
abstract: We have investigated the ability of diamines as well as basic amino acids to condense DNA onto highly ordered pyrolytic graphite with minimum damage after re-dissolution in water. Based on a bibliographic survey we briefly summarize DNA binding properties with diamines as compared to basic amino acids. Thus, solutions of DNA complexed with these linkers were drop-cast in order to deposit ultra-thin layers on the surface of HOPG in the absence or presence of Tris buffer. Atomic Force Microscopy analyses showed that, at a fixed ligand-DNA mixing ratio of 16, the mean thickness of the layers can be statistically predicted to lie in the range 0-50nm with a maximum standard deviation ±6nm, using a simple linear law depending on the DNA concentration. The morphology of the layers appears to be ligand-dependent. While the layers containing diamines present holes, those formed in the presence of basic amino acids, except for lysine, are much more compact and dense. X-ray Photoelectron Spectroscopy measurements provide compositional information indicating that, compared to the maximum number of DNA sites to which the ligands may bind, the basic amino acids Arg and His are present in large excess. Conservation of the supercoiled topology of the DNA plasmids was studied after recovery of the complex layers in water. Remarkably, arginine has the best protection capabilities whether Tris was present or not in the initial solution.
authors.affiliation: Université de Bourgogne Franche-Comté, UMR CNRS 6249 Chrono-Environnement, 16, Route de Gray, 25030 Besançon Cedex, France.
authors.forename: T T
authors.initials: TT
authors.lastname: Khalil
authors.affiliation: Université de Bourgogne Franche-Comté, UMR CNRS 6249 Chrono-Environnement, 16, Route de Gray, 25030 Besançon Cedex, France.
authors.forename: O
authors.initials: O
authors.lastname: Boulanouar
authors.affiliation: Université de Bourgogne Franche-Comté, UMR CNRS 6303Laboratoire Interdisciplinaire Carnot de Bourgogne, DTAI/Centre de micro/nano caractérisation, 9 Av. A. Savary, BP 47870, F-21078 DIJON Cedex, France.
authors.forename: O
authors.initials: O
authors.lastname: Heintz
authors.affiliation: Université de Bourgogne Franche-Comté, UMR CNRS 6249 Chrono-Environnement, 16, Route de Gray, 25030 Besançon Cedex, France. Electronic address: michel.fromm@univ-fcomte.fr.
authors.forename: M
authors.initials: M
authors.lastname: Fromm
mesh_terms: D001120:Arginine / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010957:Plasmids / Q000737:chemistry*
chemical_list: D006108:Graphite; D004247:DNA; D001120:Arginine
keywords: Amino acids; DNA thin film; Diamines; Plasmid relaxation