Interfacial Reaction Characteristic And Protective Mechanism Between Clay Minerals And DNA

Extracellular DNA released from various organisms can be adsorbed on solid particles inenvironment. This DNA can exist in the natural environment for a long time and retain itsbiological function. The aim of this study is to investigate the factors that influence DNAadsorption on different clay and to probe the mechanisms by which compound protects DNAfrom damage by heavy metal ions and nucleases, in order to approve that clay can be used asa gene repository. Montmorillonite (MMT) and rectorite (REC) are chosen as clay mineralrepresentation, salmon sperm DNA as DNA material and then studied the adsorption anddesorption properties of DNA on clay mineral. The cationic hexadecyl trimethyl ammoniumbromide (CTAB) is chosen to exchange with the hydrated cations of the interlayer to modifyMMT and REC. DNA-clay complexes were prepared, and the surface microstructure changesof these clays were analyzed by XRD, FTIR. And cyclic voltammetry, UV spectroscopy,circular dichroism and electrophoresis were used to analyze the protective effect of theDNA-clay complexes. The fixed and protection mechanism of DNA by clay were summarized.The results were shown as below：1. DNA-clay complexes were prepared. The results of XRD and FTIR demonstrate thatDNA intercalated into the CTAB modified clay mineral layers. The expanded layer space andthe changed of surface electric charge of modified clay that have made the clay minerals moreaffinity for DNA. CTAB in layer of clay attracted DNA molecules intercalate into the claymineral layers.2. Various factors such as the adsorbent dosage, pH value, the concentration of DNA andthe ions in solution were investigated. The DNA adsorbed on original clay minerals effectedby pH value and ions, and the amount of DNA adsorbed on MMT and REC is quite a little.The mechanisms for DNA adsorption on clay involve electrostatic forces, cation bridging andligand exchange. The fixation of DNA by modified clay minerals was significantly enhanced,and not effect by pH value. The amout of DNA fixed by modified clay minerals is muchlarger than adsorbed on original clay minerals, and the DNA can’t desorb easily.3. The protective effect of compound for DNA analysised by experiments. Heavy metalsdamage the structure of DNA, show the hypochromic effect and bathochromic shift. Howeverthe released DNA didn’t show the same phenomenon. Electrophoresis results also show thatclay minerals have a protective effect on DNA aganist degradation by DNase I. On one hand,clay minerals can adsorb heavy metal ions in solution, thereby reducing the threat to the DNAmolecule, on the other hand, the modified clay minerals acted as the shield prevented enzyme or metal ions from accessing to the intercalated DNA molecules.This study provide a new method for genetic preservation, provide the possibility forclay minerals used as a gene delivery vehicle, provide a simple method for the use ofmicroorganisms for environmental restoration and provide new ideas for the study of theorigin of life. Promote the development of genetically modified micro-organisms andmolecular biology.