DNA network structures induced by ferric ions on mica surfaces
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This paper explores the changes of DNA network structures with different solution concentrations of DNAs and ferric ions by atomic force microscope (AFM). AFM is a powerful tool for both the observation and manipulation of biological molecules. DNA is an important life molecule to record the biological information and it is also a natural nano material which has great potential for the fabrication of molecular devices. The mica with a flat surface can be used as a substrate for observing DNA molecules, but the combination with DNA is not controllable, and the mica surface has to be modified. Here, we used ferric ions to induce DNA network structures and they were investigated by AFM. It was observed that when the concentration of DNA solution was low, there was no DNA network structures formed, and when the concentration of DNA solution was increased to 200-280ng/ul, DNA network structures were clearly formed.Summary Analyses of individual biomolecules, like DNA, or DNA–protein complexes, via atomic force microscopy, require ‘gentle’ methods to immobilize DNA on surfaces, which allow the ensemble of molecules to adopt conformations dictated primarily by their physical characteristics, and which possibly permit the use of a wide selection of buffers. We show that poly‐ l ‐ornithine‐coated mica is a good substrate for fast, reliable deposition of DNA for wet or dry imaging. The surface firmly secures DNA, which retains the B‐form helical rise (0.34 nm bp −1 ). The conformations of DNA that result are reminiscent of three‐dimensional random coils projected on to a plane. The contrast is good, especially in solution, and buffers with physiological concentrations of salt with or without divalent cations may be used. This is important for comparison of scanning probe microscopy results with those obtained by different techniques.
Scanning Force Microscopy
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Abstract In this study, the topography of human topoisomerase I (TOPO I) on mica surfaces in air and in liquid has been studied by atomic force microscopy (AFM). The average height of TOPO I on mica surface in air measured by AFM was 2.59±0.32 nm. After adsorption of the 0.3 U/µl TOPO I on mica surfaces for 2 h, and then imaged in liquid by AFM, well‐separated single TOPO I was observed. The average height of TOPO I on mica surfaces in liquid measured by AFM was 2.93±0.42 nm. After adsorption of the 4 U/µl TOPO I on mica surfaces for 1.5 h, TOPO I monolayer can be formed. The produced TOPO I monolayer on mica was flat and exhibited good stability. SCANNING 31: 160–166, 2009. © 2009 Wiley Periodicals, Inc.
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Phlogopite mica surfaces have been observed under various conditions by an atomic force microscope (AFM). Although the AFM images change with the scan directions, we suppose that the hexagonal arrays which appeared in the AFM images are oxygen atoms from the observations of phlogopite mica surfaces after an ionexchange. Similar periodic structure images were obtained in water and in silicone oil as well as in air. Particularly clear images were obtained in pure water.
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Summary We used different methods to modify a mica surface with 3‐aminopropyltriethoxysilane (APTES), and then used it as substrate to immobilize DNA for atomic force microscopy (AFM) observation. The evaporation method and solution modifying method were investigated and evaluated. The solution modifying method was found to be relatively simple and effective. Using an APTES solution‐modified mica surface, DNA immobilization appeared more reproducible and it could be imaged in liquid. The mixed solution of APTES and DNA was dropped directly onto the mica surface for AFM imaging. We found that DNA can condense in APTES water solutions. Toroids, rods and intermediate structures of condensation were captured by AFM.
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Large DNA molecules remain difficult to be imaged by atomic force microscopy (AFM) because of the tendency of aggregation. A method is described to align long DNA fibers in a single direction on unmodified mica to facilitate AFM studies. The clear background, minimal overstretching, high reproducibility and convenience of this aligning procedure make it useful for physical mapping of genome regions and the studies of DNA-protein complexes.
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The surface topography of mica modified by 3-(trimethoxysilyl)propyl methacrylate(KH-570) was studied by atomic force microscope(AFM).Surface parameters such as roughness Rq,particle height D and the highest value at Z direction were measured.The influence of several factors on the surface topography of modified mica was investigated,including rinse,the concentration of KH-570 and the order of rinse and drying.The results indicated that the value of Rq was affected by the point defect on mica surface,rinse and the disposal after modification,while the morphology of KH-570 molecular aggregate was depended on the concentration of KH-570.As the concentration reduced,the morphology changed from cross-linked web to divergent points.
Morphology
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