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Tham khảo tài liệu 'nanotechnology science and computation part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Multicomponent Assemblies Including Long DNA and Nanoparticles 201 Fig. 1. Schematic illustration of the procedure for forming a chip-integrated nanowire a DNA and microstructured chip as building blocks b various stretching methods c DNA positioned in an electrode gap d binding of metal ions or particles and subsequent enhancement lead to a metallized nanowire are used in our workgroup. The work on the optimization of the parameters for example DNA concentration buffer conditions and conditions for the surface modification steps is very important but often tedious. Our experiments have shown that droplet sizes between 0.5 and 1 pl and DNA concentrations between 0.6 and 6 ng pl-1 are practicable. Also surface modification with a simple PDMS polydimethylsiloxane vapor treatment in a petri dish offers a possibility to obtain suitable surfaces for the stretching and positioning of DNA strands. 2.1 Immobilization on Mica A simple method for stretching DNA on mica has been described by Li et al. 46 and Cherny et al. 15 . The DNA solution is incubated on one side of the piece of mica for some minutes and then blown off slowly at an angle of 45 . The functionalization of the surface is provided by cleavage of the mica. Subsequently applied magnesium ions are then able to bridge the net negatively charged surface and the negative backbone of the DNA. However mica is not suitable for further technological applications because there is no easy possibility to contact the immobilized molecules and it is not very stable 202 A. Wolff A. Csaki W. Fritzsche Table 1. Overview of methods for stretching DNA Force Method Magnetic Magnetic tweezers Smith et al. 86 Optical Laser tweezers Perkins et al. 75 76 Moving interface Drying droplet Bensimon et al. 7 8 Jing et al. 39 Bulk fluid flow Dielectric Controlled meniscus motion Otobe and Ohtani 69 Moving meniscus Michalet et al. 60 Sliding of a coverslip edge Yokota et al. 107 Gas flow-driven droplet Li et al. 46 Spin stretching Yokota .
