Singal Molecular Force Spectroscopy System Based On Singal Beam Optical Tweezers

Single Molecular Force Spectrometry is an important research method in molecular biology.Since most biological reactions are accompanied by interactions between biological molecules,the study of the mechanical properties of biological molecules helps us to reveal these processes from the microscopic addition.Optical tweezers is an important method of force spectroscopy measurement for single molecule.In this thesis,a single-beam optical tweezers system based on optical momentum collection is designed for single-molecule force spectrum measurement experiments.The main research points of this project are as follows:First,The principle of trapping particles by an optical tweezer is explained by electromagnetic model,and Maxwell equation is solved by T matrix method based on the theory of electromagnetic model.The three-dimensional model of radiation force on particles in optical trap is established,and the effects of various parameters in optical tweezers system on the trapping performance of optical tweezers are analyzed.Second,on the basis of traditional stiffness method for measuring optical trap force,the method of collecting photomomentum is introduced.According to the principle of conservation of photon momentum in the process of propagation,the change of photomomentum before and after laser interacting with particles is calculated to get the value of optical trap force.Meanwhile,the collecting method of photomomentum is given.The position sensor PSD and the intensity sensor PD are used to receive scattered light from the sensor.And the relationship between trapping force and the output signal of the sensor is deduced.The feasibility of photodynamic force measurement is proved theoretically.Third,the measurement method of molecular type variables in single molecule force spectrum measurement experiment is designed.Firstly,the displacement information of optical trap on the focus plane is obtained by PSD measurement of position sensor.Then the relative position of particles and optical trap center is calculated by the stiffness of optical trap and optical trap force.Combining the two methods,the molecular deformation is calculated,which provides more basis for the analysis of molecular structure changes.Combining with the basic structure of single beam optical tweezers and the measurement principle of optical trap force and molecular deformation,the optical circuit and electronic control part of optical tweezers are designed.The optical path is divided into three parts: focusing,measuring and lighting part.The structure and principle of each part are introduced.According to the requirement of single molecule force spectrum measurement experiment,the active and passive control system of optical trap position is designed.At the same time,the hardware circuit and upper computer software are designed and manufactured to complete the data acquisition and control of optical tweezers system.Finally,A series of experiments were carried out to validate the performance of optical tweezers in particle capture control,optical trap force measurement,stiffness calibration and force feedback control.At the same time,the stretching experiment of preQ1 ribose-switched RNA was designed and completed.The influence of magnesium ions on the molecular properties was obtained by measuring and analyzing the force spectrum of ribose-switched RNA.The reliability of optical tweezers system in the single-molecule force spectrum measurement experiment was also verified.