Study On The Application Of Dual-trap Optical Tweezers In Single-molecular Force Spectroscopy Measurement

Proteins,as important components of organism,are involved in almost all biological processes.The biological functions of proteins are determined by their three-dimensional spatial structure,and also controlled by their dynamic behaviors in biological reactions.As a result,protein analysis requires not only static measurement of protein‘s spatial structure,but also dynamic measurement of its kinetic properties.Optical tweezers provide a method of studying the kinetic properties of proteins at single-molecule level.This helps scientists deepen their understanding of the link between proteins‘ kinetic properties and their biological functions.It also contributes to life science research.The most powerful capabilities of optical tweezers are to manipulate micron-sized particles with pico-Newton level forces and measure the displacement of the particles with nanometer resolution.This paper,on the basis of the self-built dual-beam optical trapping system,investigates the appropriate system conditions for single-molecule force spectroscopy measurement.Furthermore,force spectroscopy curves of dsDNA and some proteins are measured and analyzed in order to verify the performance of the self-built optical tweezersThe main works and progresses in this paper can be included in the following aspects:1.The background and development status of optical tweezers at home and abroad are reviewed,then with a summary of the main applications of optical tweezers in biological and physical research.Furthermore,three most representative measurement techniques in single molecule biology(optical tweezers,magnetic tweezers and atomic force microscopy)are compared.Combining with the spatial structure model of biological macromolecules,the important role of optical tweezers in the study of single molecule biology is discussed.2.The theoretical models of optical trapping force for biomolecule testing system(the dumbbell-shaped bead-DNA-protein-DNA-bead construct)are studied.Combining with the self-built optical tweezers system,main parameters affecting the single-molecule force spectroscopy measurement,including laser beam,microsphere and liquid environment,are proposed by simulation and practical experiments.The effect of thermophoretic force in different liquid environment is studied.At last,the selection scheme for each parameter is given.3.Thermodynamic and kinetic information of the protein contained in the force spectroscopy curve are studied based on the protein‘s spatial structure and the related theoretical models.Furthermore,analytical method of force spectroscopy curve is summarized.4.The feasible measurement mode and experimental process of dual-beam optical trapping system are concluded.Repetitive experiments of dsDNA and some common proteins are carried out.Their force spectroscopy curves are analyzed and compared with the theoretical model.