Study On The Kinetics Of Stretching And Patterning Of DNA Molecule Based On Evaporation Molecular Combing Technology

The visualization and manipulation aimed at single DNA molecule in solution is conductive to study the physicochemical properties and applications of DNA molecules,which accelerate the understanding of the principle of life.Meanwhile,the 2D/3D structures based on DNA can be used in micro/nano sensors which can be used as micro-detection in life sciences research area.The molecular combing technique based on liquid surface tension is simple and efficient for stretching DNA molecules.In this paper,the effects of buffer/DNA concentration on the evaporating DNA droplet,the stretched DNA molecules and the DNA self-assembled deposition pattern were investigated by fluorescence-imaging and high-precision drop shape analyzing.The main content of this paper is as follows:Firstly,DNA molecules were fully stretched by the evaporation molecular combing(EMC)on the polymethyl methacrylate(PMMA)surface.The oriented motion of DNA in the evaporating droplet,and the influence of buffer concentration,pH and substrate hydrophobicity on the combed DNA molecules,was investigated by fluorescence imaging.Secondly,the drying process of DNA droplet,varying with different buffer/DNA concentrations,was investigated by high-precision drop shape analyzing.There are two key evaporation modes in the drying process of DNA droplet:the constant contact angle(CCA)mode and the constant contact radius(CCR)mode,which were influenced by the concentration of both buffer and DNA.The CCA mode only exits in lower concentration.When the concentration increases,it will be replaced by the mixed mode.The CCR mode is common.When the concentration increases,it will last longer.It was found that the CCA mode is critical for uniformly stretching of DNA,while the CCR mode plays a key role in forming the DNA ringlike pattern.The formation of the ringlike pattern can be attributed to the co-work of the "coffee ring" effect and molecular combing through a lot of experiments and analysis.Thirdly,a polygon-mesh pattern self-organized by DNA molecules during evaporation combing was analyzed and studied.