Disassembly of DNA–ligand on mica surface: atomic force microscopy studies

Abstract

SummaryDisassembly of DNA-ligands, including DNA-methylene blue (MB) complex and DNA-Co(phen) 3 3+ complex on mica surface, were investigated by atomic force microscopy (AFM). The disassembly of these complexes occurred after they were immersed in ultra-pure water. AFM results showed that the disassembly depended strongly on bridge ions that were used to immobilize the complex onto mica surface, DNA species and ligands. When Mg 2+ was used as the bridge ion, the DNA-MB complex was completely disassembled because of the weak interactions between Mg 2+ and DNA's bases or mica surface. Although if Co 2+ was used as the bridge ion, the disassembly of the DNA-MB complex mainly depended on the species and shape of DNA. For plasmid DNA pBR 322, plasmid DNA pUC 18 and the linear DNA pBR 322/PstI, the degree of disassembly was gradually increased. Whereas if Co(phen) 3 3+ was chosen as the ligand, the disassembly of the DNA-Co(phen) 3 3+ complex was almost blocked because Co(phen) 3 3+ could hardly diffuse into the ultra-pure water. This obtained information may be useful for practical application of the AFM imaging of biological molecules, especially in liquid.

Specific DNA−Protein Interactions on Mica Investigated by Atomic Force Microscopy

“…We found that β progressively decreased with the incubation time whether or not free EcoRI was present in solution (Figure ). In agreement with a recent study, this result indicates that EcoRI irreversibly dissociates from its specific DNA site on the mica surface under strong adsorption conditions.…”