Structural properties of DNA complexes with new cationic surfactants

Recently an extensive development of electronics and photonics based on DNA (Deoxyribonucleic acid) has taken place. DNA has already been successfully employed in OLED´s, where it served as an electron blocking layer, in field effect transistors or in waveguides. Deoxyribonucleic acid is a biopolymer (polynucleotide) built from repeating units (mers) consisting of three fragments: purine or pyrimidine base, sugar and phosphoric acid. Native DNA molecule consists of a two helically twisted strands joint by hydrogen bonds formed between complementary bases. Owing to this particular structure, general properties of biological DNA differ from man-made synthetic polymers. A basic form of a polymer applied in organic electronics or photonics is a film of submicron thickness. DNA is a hydrophilic polymer and since compatible only with some exotic solvent and water. Films processed from aqueous solutions have insufficient mechanical strength. If sodium cations, ionically bound to the DNA backbone are replaced with molecules of a quarternized ammonium salt, containing a long alkyl chains, DNA becomes insoluble in water, yet become soluble in a range of alcohols, benzene, chloroform and similar solvents. This new stable form is referred to as DNA-lipid complex or simply DNA complex. Such a procedure does not change the basic electronic structure of DNA backbone. The aim of this work is to show our first result on structural X-ray diffraction studies of DNA - surfactant systems. Thermal stability studies and the evolution of diffraction patterns with wide range of temperatures were presented and discussed.