EDTA And NaCl Induced Desorption Of DNA From Mica Surface Studied By Atomic Force Microscopy

The adsorption and motion behavior of DNA at liquid-solid interface has attracted wide attention due to its extensive application in many areas including material and medicine science. The study on the adsorption behavior of DNA on substance is relatively mature at present. However, the study on the desorption behavior of DNA on substance is still in the primary stage, and new desorption methods are still need to be explored. The complexing agent EDTA and the inorganic salt NaCl were used to desorb DNA from mica surface for the first time. Atomic force microscopy(AFM) was utilized to observe the adsorption and desorption state of DNA on mica surface. The main contents of this thesis are as following:1. EDTA induced desorption of DNA from mica surface studied by AFM. By using the complexation of EDTA and divalent metal ions for first time, the DNA molecules which were adsorbed on mica surface through the glue agent of divalent metal ions were desorbed. And the different factors on the desorption degree of DNA were studied. AFM characterization indicates that the adsorption degree of DNA on mica surface increases with the increase of the DNA concentration. The desorption degree of DNA on mica surface increases with the increase of desorption time and EDTA concentration. However, it decreases with the increase of DNA concentration and DNA length. The kinds of divalent metal ions also have effects on the desorption degree of DNA. Divalent metal ions with higher affinity to EDTA will facilitate desorption of DNA from mica surface. In iddition, experiment results showed that EDTA can induce the lightly aggregation of DNA molecules.2. NaCl induced desorption of DNA from mica surface studied by AFM. By using the charge shielding effects among Na+, mica surface and phosphate groups, the DNA molecules which were adsorbed on mica surface through the glue agent of divalent metal ions were desorbed. And the different factors on the desorption degree of DNA were studied. AFM characterization results indicate that the adsorption degree of DNA on mica surface increases with the increase of DNA concentration. The desorption degree of DNA on mica surface increases with the increase of desorption time and NaCl concentration, and it decreases with the increase of DNA concentration. However, the kinds of divalent metal ions and DNA length have no influence on the desorption degree of DNA. In addition, experiment results showed that the structure of DNA molecules is little affected by NaCl.